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Implementatation of the Service locator pattern

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This commit is contained in:
MSaifAsif 2014-12-06 02:39:54 +05:00
parent 3e42a10060
commit 1cb62f543b
10 changed files with 282 additions and 0 deletions
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1
pom.xml
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@ -37,6 +37,7 @@
<module>visitor</module>
<module>double-checked-locking</module>
<module>servant</module>
<module>service-locator</module>
</modules>
<build>

74
service-locator/etc/model.ucls Normal file
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@ -0,0 +1,74 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.7" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<interface id="1" language="java" name="com.iluwater.Service" project="service-locator"
file="/service-locator/src/main/java/com/iluwater/Service.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="110" y="182"/>
<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="2" language="java" name="com.iluwater.ServiceImpl" project="service-locator"
file="/service-locator/src/main/java/com/iluwater/ServiceImpl.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="342" 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>
<class id="3" language="java" name="com.iluwater.ServiceLocator" project="service-locator"
file="/service-locator/src/main/java/com/iluwater/ServiceLocator.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="702" y="175"/>
<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="4" language="java" name="com.iluwater.ServiceCache" project="service-locator"
file="/service-locator/src/main/java/com/iluwater/ServiceCache.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="397" y="81"/>
<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>
<realization id="5">
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="1"/>
</realization>
<association id="6">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="7" name="serviceCache">
<position height="0" width="0" x="0" y="0"/>
</attribute>
<multiplicity id="8" minimum="0" maximum="1">
<position height="0" width="0" x="0" y="0"/>
</multiplicity>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<association id="9">
<end type="SOURCE" refId="4" navigable="false">
<attribute id="10" name="serviceCache">
<position height="0" width="0" x="0" y="0"/>
</attribute>
<multiplicity id="11" minimum="0" maximum="2147483647">
<position height="0" width="0" x="0" y="0"/>
</multiplicity>
</end>
<end type="TARGET" refId="1" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<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>

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service-locator/pom.xml Normal file
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<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">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>service-locator</artifactId>
</project>

20
service-locator/src/main/java/com/iluwater/App.java Normal file
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@ -0,0 +1,20 @@
package com.iluwater;
/**
* Service locator pattern, used to lookup jndi services
* and cache them for subsequent requests.
* @author saifasif
*
*/
public class App {
public static void main(String[] args) {
Service service = ServiceLocator.getService("jndi/serviceA");
service.execute();
service = ServiceLocator.getService("jndi/serviceB");
service.execute();
service = ServiceLocator.getService("jndi/serviceA");
service.execute();
service = ServiceLocator.getService("jndi/serviceA");
service.execute();
}
}

29
service-locator/src/main/java/com/iluwater/InitContext.java Normal file
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@ -0,0 +1,29 @@
package com.iluwater;
/**
* For JNDI lookup of services from the web.xml. Will match name of the service name that
* is being requested and return a newly created service object with the name
* @author saifasif
*
*/
public class InitContext {
/**
* Perform the lookup based on the service name. The returned object will need to be
* casted into a {@link Service}
* @param serviceName
* @return
*/
public Object lookup(String serviceName){
if( serviceName.equals("jndi/serviceA") ){
System.out.println("Looking up service A and creating new serivce for A");
return new ServiceImpl("jndi/serviceA");
} else if( serviceName.equals("jndi/serviceB") ){
System.out.println("Looking up service B and creating new serivce for B");
return new ServiceImpl("jndi/serviceB");
} else {
return null;
}
}
}

29
service-locator/src/main/java/com/iluwater/Service.java Normal file
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@ -0,0 +1,29 @@
package com.iluwater;
/**
* This is going to be the parent service interface which we will
* use to create our services. All services will have a
* <li>service name</li>
* <li>unique id</li>
* <li>execution work flow</li>
* @author saifasif
*
*/
public interface Service {
/*
* The human readable name of the service
*/
public String getName();
/*
* Unique ID of the particular service
*/
public int getId();
/*
* The workflow method that defines what this service does
*/
public void execute();
}

46
service-locator/src/main/java/com/iluwater/ServiceCache.java Normal file
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@ -0,0 +1,46 @@
package com.iluwater;
import java.util.HashMap;
import java.util.Map;
/**
* The service cache implementation which will cache services that are being created.
* On first hit, the cache will be empty and thus any service that is being requested, will be
* created fresh and then placed into the cache map. On next hit, if same service name will
* be requested, it will be returned from the cache
* @author saifasif
*
*/
public class ServiceCache {
private Map<String, Service> serviceCache;
public ServiceCache() {
serviceCache = new HashMap<String, Service>();
}
/**
* Get the service from the cache. null if no service is found matching the
* name
* @param serviceName
* @return {@link Service}
*/
public Service getService(String serviceName){
Service cachedService = null;
for (String serviceJndiName : serviceCache.keySet()){
if( serviceJndiName.equals( serviceName ) ){
cachedService = serviceCache.get(serviceJndiName);
System.out.println("(cache call) Fetched service " + cachedService.getName() + "("+cachedService.getId()+") from cache... !");
}
}
return cachedService;
}
/**
* Adds the service into the cache map
* @param newService
*/
public void addService(Service newService){
serviceCache.put(newService.getName(), newService);
}
}

37
service-locator/src/main/java/com/iluwater/ServiceImpl.java Normal file
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@ -0,0 +1,37 @@
package com.iluwater;
/**
* This is a single service implementation of a sample service. This is the actual
* service that will process the request. The reference for this service is to
* be looked upon in the JNDI server that can be set in the web.xml deployment descriptor
* @author saifasif
*
*/
public class ServiceImpl implements Service {
private String serviceName;
private int id;
public ServiceImpl(String serviceName) {
// set the service name
this.serviceName = serviceName;
// Generate a random id to this service object
this.id = (int)Math.floor(Math.random()*1000)+1;
}
@Override
public String getName() {
return serviceName;
}
@Override
public int getId() {
return id;
}
@Override
public void execute() {
System.out.println("Service " + getName() + " is now executing with id " + getId());
}
}

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service-locator/src/main/java/com/iluwater/ServiceLocator.java Normal file
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@ -0,0 +1,37 @@
package com.iluwater;
/**
* The service locator module.
* Will fetch service from cache, otherwise creats a fresh service and update cache
*
* @author saifasif
*
*/
public class ServiceLocator {
private static ServiceCache serviceCache = new ServiceCache();
/**
* Fetch the service with the name param from the cache first,
* if no service is found, lookup the service from the {@link InitContext} and
* then add the newly created service into the cache map for future requests.
* @param serviceJndiName
* @return {@link Service}
*/
public static Service getService(String serviceJndiName){
Service serviceObj = serviceCache.getService(serviceJndiName);
if ( serviceObj != null ){
return serviceObj;
} else {
/*
* If we are unable to retrive anything from cache, then
* lookup the service and add it in the cache map
*/
InitContext ctx = new InitContext();
serviceObj = (Service) ctx.lookup(serviceJndiName);
serviceCache.addService(serviceObj);
return serviceObj;
}
}
}