Merge pull request #427 from surgeforward/297

#297 Create API Gateway pattern

api-gateway/README.md

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+---
+layout: pattern
+title: API Gateway
+folder: api-gateway
+permalink: /patterns/api-gateway/
+categories: Architectural
+tags:
+- Java
+- Difficulty-Intermediate
+- Spring
+---
+
+## Intent
+
+Aggregate calls to microservices in a single location: the API Gateway. The user makes a single
+call to the API Gateway, and the API Gateway then calls each relevant microservice.
+
+![alt text](./etc/api-gateway.png "API Gateway")
+
+## Applicability
+
+Use the API Gateway pattern when
+
+* you're also using the Microservices pattern and need a single point of aggregation for your
+microservice calls
+
+## Credits
+
+* [microservices.io - API Gateway](http://microservices.io/patterns/apigateway.html)
+* [NGINX - Building Microservices: Using an API Gateway](https://www.nginx.com/blog/building-microservices-using-an-api-gateway/)

api-gateway/api-gateway-service/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2014 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>api-gateway</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.12.0-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+  <artifactId>api-gateway-service</artifactId>
+  <packaging>jar</packaging>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-dependencies</artifactId>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-webmvc</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.httpcomponents</groupId>
+      <artifactId>httpclient</artifactId>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+        <version>${spring-boot.version}</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>repackage</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import javax.annotation.Resource;
+
+/**
+ * The ApiGateway aggregates calls to microservices based on the needs of the individual clients.
+ */
+@RestController
+public class ApiGateway {
+
+  @Resource
+  private ImageClient imageClient;
+
+  @Resource
+  private PriceClient priceClient;
+
+  /**
+   * Retrieves product information that desktop clients need
+   * @return Product information for clients on a desktop
+   */
+  @RequestMapping("/desktop")
+  public DesktopProduct getProductDesktop() {
+    DesktopProduct desktopProduct = new DesktopProduct();
+    desktopProduct.setImagePath(imageClient.getImagePath());
+    desktopProduct.setPrice(priceClient.getPrice());
+    return desktopProduct;
+  }
+
+  /**
+   * Retrieves product information that mobile clients need
+   * @return Product information for clients on a mobile device
+   */
+  @RequestMapping("/mobile")
+  public MobileProduct getProductMobile() {
+    MobileProduct mobileProduct = new MobileProduct();
+    mobileProduct.setPrice(priceClient.getPrice());
+    return mobileProduct;
+  }
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/App.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * With the Microservices pattern, a client may need data from multiple different microservices.
+ * If the client called each microservice directly, that could contribute to longer load times,
+ * since the client would have to make a network request for each microservice called. Moreover,
+ * having the client call each microservice directly ties the client to that microservice - if the
+ * internal implementations of the microservices change (for example, if two microservices are
+ * combined sometime in the future) or if the location (host and port) of a microservice changes,
+ * then every client that makes use of those microservices must be updated.
+ *
+ * <p>
+ * The intent of the API Gateway pattern is to alleviate some of these issues. In the API Gateway
+ * pattern, an additional entity (the API Gateway) is placed between the client and the
+ * microservices. The job of the API Gateway is to aggregate the calls to the microservices.
+ * Rather than the client calling each microservice individually, the client calls the API Gateway
+ * a single time. The API Gateway then calls each of the microservices that the client needs.
+ *
+ * <p>
+ * This implementation shows what the API Gateway pattern could look like for an e-commerce site.
+ * The {@link ApiGateway} makes calls to the Image and Price microservices using the
+ * {@link ImageClientImpl} and {@link PriceClientImpl} respectively. Customers viewing the site on a
+ * desktop device can see both price information and an image of a product, so the {@link ApiGateway}
+ * calls both of the microservices and aggregates the data in the {@link DesktopProduct} model.
+ * However, mobile users only see price information; they do not see a product image. For mobile
+ * users, the {@link ApiGateway} only retrieves price information, which it uses to populate the
+ * {@link MobileProduct}.
+ */
+@SpringBootApplication
+public class App {
+
+  /**
+   * Program entry point
+   *
+   * @param args
+   *          command line args
+   */
+  public static void main(String[] args) {
+    SpringApplication.run(App.class, args);
+  }
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+/**
+ * Encapsulates all of the information that a desktop client needs to display a product.
+ */
+public class DesktopProduct {
+  /**
+   * The price of the product
+   */
+  private String price;
+
+  /**
+   * The path to the image of the product
+   */
+  private String imagePath;
+
+  public String getPrice() {
+    return price;
+  }
+
+  public void setPrice(String price) {
+    this.price = price;
+  }
+
+  public String getImagePath() {
+    return imagePath;
+  }
+
+  public void setImagePath(String imagePath) {
+    this.imagePath = imagePath;
+  }
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClient.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+/**
+ * An interface used to communicate with the Image microservice
+ */
+public interface ImageClient {
+  String getImagePath();
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java

@@ -0,0 +1,56 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.util.EntityUtils;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+/**
+ * An adapter to communicate with the Image microservice
+ */
+@Component
+public class ImageClientImpl implements ImageClient{
+  /**
+   * Makes a simple HTTP Get request to the Image microservice
+   * @return The path to the image
+   */
+  @Override
+  public String getImagePath() {
+    String response = null;
+    try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
+      HttpGet httpGet = new HttpGet("http://localhost:50005/image-path");
+      try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
+        response = EntityUtils.toString(httpResponse.getEntity());
+      }
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+    return response;
+  }
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/MobileProduct.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+/**
+ * Encapsulates all of the information that mobile client needs to display a product.
+ */
+public class MobileProduct {
+  /**
+   * The price of the product
+   */
+  private String price;
+
+  public String getPrice() {
+    return price;
+  }
+
+  public void setPrice(String price) {
+    this.price = price;
+  }
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClient.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+/**
+ * An interface used to communicate with the Price microservice
+ */
+public interface PriceClient {
+  String getPrice();
+}

api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.util.EntityUtils;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+/**
+ * An adapter to communicate with the Price microservice
+ */
+@Component
+public class PriceClientImpl implements PriceClient{
+  /**
+   * Makes a simple HTTP Get request to the Price microservice
+   * @return The price of the product
+   */
+  @Override
+  public String getPrice() {
+    String response = null;
+    try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
+      HttpGet httpGet = new HttpGet("http://localhost:50006/price");
+      try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
+        response = EntityUtils.toString(httpResponse.getEntity());
+      }
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+    return response;
+  }
+}

api-gateway/api-gateway-service/src/main/resources/application.properties

@@ -0,0 +1,24 @@
+#
+# The MIT License
+# Copyright (c) 2014 Ilkka Seppälä
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+#
+
+server.port=50004

api-gateway/api-gateway-service/src/test/java/com/iluwatar/api/gateway/ApiGatewayTest.java

@@ -0,0 +1,78 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.api.gateway;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
+
+public class ApiGatewayTest {
+
+  @InjectMocks
+  private ApiGateway apiGateway;
+
+  @Mock
+  private ImageClient imageClient;
+
+  @Mock
+  private PriceClient priceClient;
+
+  @Before
+  public void setup() {
+    MockitoAnnotations.initMocks(this);
+  }
+
+  /**
+   * Tests getting the data for a desktop client
+   */
+  @Test
+  public void testGetProductDesktop() {
+    String imagePath = "/product-image.png";
+    String price = "20";
+    when(imageClient.getImagePath()).thenReturn(imagePath);
+    when(priceClient.getPrice()).thenReturn(price);
+
+    DesktopProduct desktopProduct = apiGateway.getProductDesktop();
+
+    assertEquals(price, desktopProduct.getPrice());
+    assertEquals(imagePath, desktopProduct.getImagePath());
+  }
+
+  /**
+   * Tests getting the data for a mobile client
+   */
+  @Test
+  public void testGetProductMobile() {
+    String price = "20";
+    when(priceClient.getPrice()).thenReturn(price);
+
+    MobileProduct mobileProduct = apiGateway.getProductMobile();
+
+    assertEquals(price, mobileProduct.getPrice());
+  }
+}

api-gateway/etc/api-gateway.ucls

@@ -0,0 +1,97 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.api.gateway.ApiGateway" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="125" y="87"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="com.iluwatar.api.gateway.DesktopProduct" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="388" y="109"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <interface id="3" language="java" name="com.iluwatar.api.gateway.ImageClient" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClient.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="81" width="129" x="13" y="197"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </interface>  
+  <class id="4" language="java" name="com.iluwatar.api.gateway.ImageClientImpl" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="99" width="129" x="13" y="325"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="5" language="java" name="com.iluwatar.api.gateway.MobileProduct" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/MobileProduct.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="376" y="293"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <interface id="6" language="java" name="com.iluwatar.api.gateway.PriceClient" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClient.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="222" y="231"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </interface>  
+  <class id="7" language="java" name="com.iluwatar.api.gateway.PriceClientImpl" project="api-gateway" 
+    file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java" binary="false" corner="BOTTOM_RIGHT">
+    <position height="-1" width="-1" x="223" y="374"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="8">    
+    <end type="SOURCE" refId="1" navigable="false">      
+      <attribute id="9" name="imageClient"/>      
+      <multiplicity id="10" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="3" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <realization id="11">    
+    <end type="SOURCE" refId="4"/>    
+    <end type="TARGET" refId="3"/>  
+  </realization>  
+  <association id="12">    
+    <end type="SOURCE" refId="1" navigable="false">      
+      <attribute id="13" name="priceClient"/>      
+      <multiplicity id="14" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="6" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <realization id="15">    
+    <end type="SOURCE" refId="7"/>    
+    <end type="TARGET" refId="6"/>  
+  </realization>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

api-gateway/image-microservice/etc/image-microservice.ucls

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.image.microservice.ImageController" project="image-microservice" 
+    file="/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageController.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="87" y="61"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

api-gateway/image-microservice/pom.xml

@@ -0,0 +1,79 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2014 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>api-gateway</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.12.0-SNAPSHOT</version>
+  </parent>
+
+  <modelVersion>4.0.0</modelVersion>
+  <artifactId>image-microservice</artifactId>
+  <packaging>jar</packaging>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-dependencies</artifactId>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-webmvc</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+        <version>${spring-boot.version}</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>repackage</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

api-gateway/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageApplication.java

@@ -0,0 +1,43 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.image.microservice;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * ImageApplication starts up Spring Boot, exposing endpoints for the Image microservice through
+ * the {@link ImageController}.
+ */
+@SpringBootApplication
+public class ImageApplication {
+
+  /**
+   * Microservice entry point
+   * @param args
+   *          command line args
+   */
+  public static void main(String[] args) {
+    SpringApplication.run(ImageApplication.class, args);
+  }
+}

api-gateway/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageController.java

@@ -0,0 +1,43 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.image.microservice;
+
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * Exposes the Image microservice's endpoints
+ */
+@RestController
+public class ImageController {
+
+  /**
+   * An endpoint for a user to retrieve an image path
+   * @return An image path
+   */
+  @RequestMapping(value = "/image-path", method = RequestMethod.GET)
+  public String getImagePath() {
+    return "/product-image.png";
+  }
+}

api-gateway/image-microservice/src/main/resources/application.properties

@@ -0,0 +1,24 @@
+#
+# The MIT License
+# Copyright (c) 2014 Ilkka Seppälä
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+#
+
+server.port=50005

api-gateway/image-microservice/src/test/java/com/iluwatar/image/microservice/ImageControllerTest.java

@@ -0,0 +1,37 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.image.microservice;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ImageControllerTest {
+  @Test
+  public void testGetImagePath() {
+    ImageController imageController = new ImageController();
+
+    String imagePath = imageController.getImagePath();
+
+    Assert.assertEquals("/product-image.png", imagePath);
+  }
+}

api-gateway/pom.xml

@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2014 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>java-design-patterns</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.12.0-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+  <artifactId>api-gateway</artifactId>
+  <packaging>pom</packaging>
+
+  <modules>
+    <module>image-microservice</module>
+    <module>price-microservice</module>
+    <module>api-gateway-service</module>
+  </modules>
+</project>

api-gateway/price-microservice/etc/price-microservice.ucls

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.price.microservice.PriceController" project="price-microservice" 
+    file="/price-microservice/src/main/java/com/iluwatar/price/microservice/PriceController.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="82" y="63"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

api-gateway/price-microservice/pom.xml

@@ -0,0 +1,79 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2014 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>api-gateway</artifactId>
+    <groupId>com.iluwatar</groupId>
+    <version>1.12.0-SNAPSHOT</version>
+  </parent>
+
+  <modelVersion>4.0.0</modelVersion>
+  <artifactId>price-microservice</artifactId>
+  <packaging>jar</packaging>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-dependencies</artifactId>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-webmvc</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+        <version>${spring-boot.version}</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>repackage</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

api-gateway/price-microservice/src/main/java/com/iluwatar/price/microservice/PriceApplication.java

@@ -0,0 +1,43 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.price.microservice;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * PriceApplication starts up Spring Boot, exposing endpoints for the Price microservice through
+ * the {@link PriceController}.
+ */
+@SpringBootApplication
+public class PriceApplication {
+
+  /**
+   * Microservice entry point
+   * @param args
+   *          command line args
+   */
+  public static void main(String[] args) {
+    SpringApplication.run(PriceApplication.class, args);
+  }
+}

api-gateway/price-microservice/src/main/java/com/iluwatar/price/microservice/PriceController.java

@@ -0,0 +1,43 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.price.microservice;
+
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * Exposes the Price microservice's endpoints
+ */
+@RestController
+public class PriceController {
+
+  /**
+   * An endpoint for a user to retrieve a product's price
+   * @return A product's price
+   */
+  @RequestMapping(value = "/price", method = RequestMethod.GET)
+  public String getPrice() {
+    return "20";
+  }
+}

api-gateway/price-microservice/src/main/resources/application.properties

@@ -0,0 +1,24 @@
+#
+# The MIT License
+# Copyright (c) 2014 Ilkka Seppälä
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+#
+
+server.port=50006

api-gateway/price-microservice/src/test/java/com/iluwatar/price/microservice/PriceControllerTest.java

@@ -0,0 +1,37 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.price.microservice;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class PriceControllerTest {
+  @Test
+  public void testgetPrice() {
+    PriceController priceController = new PriceController();
+
+    String price = priceController.getPrice();
+
+    Assert.assertEquals("20", price);
+  }
+}

pom.xml

@@ -33,6 +33,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<hibernate.version>5.0.1.Final</hibernate.version>
 		<spring.version>4.2.4.RELEASE</spring.version>
+    <spring-boot.version>1.3.3.RELEASE</spring-boot.version>
 		<spring-data.version>1.9.2.RELEASE</spring-data.version>
 		<h2.version>1.4.190</h2.version>
 		<junit.version>4.12</junit.version>
@@ -46,6 +47,7 @@
 		<systemrules.version>1.15.1</systemrules.version>
 		<mockito.version>1.10.19</mockito.version>
 		<hierarchical-junit-runner-version>4.12.1</hierarchical-junit-runner-version>
+    <apache-httpcomponents.version>4.5.2</apache-httpcomponents.version>
 	</properties>
 	<modules>
 		<module>abstract-factory</module>
@@ -116,6 +118,7 @@
 		<module>publish-subscribe</module>
 		<module>delegation</module>
 		<module>event-driven-architecture</module>
+		<module>api-gateway</module>
 		<module>factory-kit</module>
 		<module>feature-toggle</module>
 		<module>value-object</module>
@@ -142,11 +145,33 @@
 				<artifactId>spring-test</artifactId>
 				<version>${spring.version}</version>
 			</dependency>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-dependencies</artifactId>
+        <version>${spring-boot.version}</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
             		<dependency>
 				<groupId>org.springframework.data</groupId>
 				<artifactId>spring-data-jpa</artifactId>
 				<version>${spring-data.version}</version>
 			</dependency>
+      <dependency>
+        <groupId>org.springframework</groupId>
+        <artifactId>spring-webmvc</artifactId>
+        <version>${spring.version}</version>
+      </dependency>
+      <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-web</artifactId>
+        <version>${spring-boot.version}</version>
+      </dependency>
+      <dependency>
+        <groupId>org.apache.httpcomponents</groupId>
+        <artifactId>httpclient</artifactId>
+        <version>${apache-httpcomponents.version}</version>
+      </dependency>
 			<dependency>
 				<groupId>com.h2database</groupId>
 				<artifactId>h2</artifactId>