#631 - Partial Response : Implement Field to json conversion

partial-response/src/main/java/com/iluwatar/partialresponse/FieldJsonMapper.java

@@ -24,6 +24,8 @@
 
 package com.iluwatar.partialresponse;
 
+import java.lang.reflect.Field;
+
 /**
  * Map a video to json
  */
@@ -34,7 +36,25 @@ public class FieldJsonMapper {
    * @param fields fields information to get
    * @return json of required fields from video
    */
-  public String toJson(Video video, String[] fields) {
-    return null;
+  public String toJson(Video video, String[] fields) throws Exception {
+    StringBuilder json = new StringBuilder().append("{");
+
+    for (int i = 0, fieldsLength = fields.length; i < fieldsLength; i++) {
+      json.append(getString(video, Video.class.getDeclaredField(fields[i])));
+      if (i != fieldsLength - 1) {
+        json.append(",");
+      }
+    }
+    json.append("}");
+    return json.toString();
+  }
+
+  private String getString(Video video, Field declaredField) throws IllegalAccessException {
+    declaredField.setAccessible(true);
+    Object value = declaredField.get(video);
+    if (declaredField.get(video) instanceof Integer) {
+      return "\"" + declaredField.getName() + "\"" + ": " + value;
+    }
+    return "\"" + declaredField.getName() + "\"" + ": " + "\"" + value.toString() + "\"";
   }
 }

partial-response/src/main/java/com/iluwatar/partialresponse/Video.java

@@ -59,7 +59,7 @@ public class Video {
   @Override
   public String toString() {
     return "{"
-        + "\"id\": \"" + id + "\","
+        + "\"id\": " + id + ","
         + "\"title\": \"" + title + "\","
         + "\"length\": " + length + ","
         + "\"description\": \"" + description + "\","

partial-response/src/main/java/com/iluwatar/partialresponse/VideoResource.java

@@ -48,7 +48,7 @@ public class VideoResource {
    * @param fields fields to get information about
    * @return json of specified fields of particular video by id
    */
-  public String getDetails(Integer id, String... fields) {
+  public String getDetails(Integer id, String... fields) throws Exception {
     if (fields.length == 0) {
       return videos.get(id).toString();
     }

partial-response/src/test/java/com/iluwatar/partialresponse/FieldJsonMapperTest.java

@@ -0,0 +1,53 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Gopinath Langote
+ *
+ * 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.partialresponse;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * tests {@link FieldJsonMapper}.
+ */
+public class FieldJsonMapperTest {
+  private FieldJsonMapper mapper;
+
+  @Before
+  public void setUp() {
+    mapper = new FieldJsonMapper();
+  }
+
+  @Test
+  public void shouldReturnJsonForSpecifiedFieldsInVideo() throws Exception {
+    String[] fields = new String[]{"id", "title", "length"};
+    Video video = new Video(2, "Godzilla Resurgence", 120, "Action & drama movie|", "Hideaki Anno", "Japanese");
+
+    String jsonFieldResponse = mapper.toJson(video, fields);
+
+    String expectedDetails = "{\"id\": 2,\"title\": \"Godzilla Resurgence\",\"length\": 120}";
+    assertEquals(expectedDetails, jsonFieldResponse);
+  }
+}

partial-response/src/test/java/com/iluwatar/partialresponse/VideoResourceTest.java

@@ -58,19 +58,19 @@ public class VideoResourceTest {
   }
 
   @Test
-  public void shouldGiveVideoDetailsById() {
+  public void shouldGiveVideoDetailsById() throws Exception {
     String actualDetails = resource.getDetails(1);
 
-    String expectedDetails = "{\"id\": \"1\",\"title\": \"Avatar\",\"length\": 178,\"description\": "
+    String expectedDetails = "{\"id\": 1,\"title\": \"Avatar\",\"length\": 178,\"description\": "
         + "\"epic science fiction film\",\"director\": \"James Cameron\",\"language\": \"English\",}";
     assertEquals(expectedDetails, actualDetails);
   }
 
   @Test
-  public void shouldGiveSpecifiedFieldsInformationOfVideo() {
-    String[] fields = new String[]{"title", "length"};
+  public void shouldGiveSpecifiedFieldsInformationOfVideo() throws Exception {
+    String[] fields = new String[]{"id", "title", "length"};
 
-    String expectedDetails = "{\"id\": \"1\",\"title\": \"Avatar\",\"length\": 178}";
+    String expectedDetails = "{\"id\": 1,\"title\": \"Avatar\",\"length\": 178}";
     when(fieldJsonMapper.toJson(any(Video.class), eq(fields))).thenReturn(expectedDetails);
 
     String actualFieldsDetails = resource.getDetails(2, fields);