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How To Create Rest WebServices With GUICE And Jersey

Posted on the 03 September 2015 by Abhishek Somani @somaniabhi
This is a simple example of how to use Google Guice , with Jersey to create JAX-RS web services , which can be deployed to any servlet container like Tomcat , Jboss , GlassFish etc . We will be creating a simple Transaction Service , which will Create , update , and query Transactions . For this example , we are not using any database but a simple hashmap to store it . So , first of all lets have a look at our maven pom.xml file . I have added dependency for Guice(jersey-guice) which is a guice extension of jersey.

<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>
<groupId>com.javaroots</groupId>
<artifactId>codeChallenge</artifactId>
<version>1.0</version>
<packaging>war</packaging>
<name>Code Challenge</name>
<description>Code Challenge Sample Prject</description>
<dependencies>
<dependency>
<groupId>com.sun.jersey.contribs</groupId>
<artifactId>jersey-guice</artifactId>
<version>1.19</version>
</dependency>
<dependency>
<groupId>com.sun.jersey</groupId>
<artifactId>jersey-json</artifactId>
<version>1.19</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.9.5</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.1</version>
</dependency>
</dependencies>
<build>
<finalName>${artifactId}</finalName>
</build>
</project>
Now we have DAO like this .

package com.javaroots.dao;
import java.util.List;
import com.javaroots.model.Transaction;
public interface TransferDAO {
public void create(Transaction tr);
public Transaction get(Long id) ;
}

package com.javaroots.dao.impl;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import com.google.inject.Singleton;
import com.javaroots.dao.TransferDAO;
import com.javaroots.model.Transaction;
@Singleton
public class TransferDAOMemoryImpl implements TransferDAO{
private ReadWriteLock lock ;
private Lock readLock ;
private Lock writeLock ;
private Map store ;
public TransferDAOMemoryImpl()
{
lock = new ReentrantReadWriteLock();
readLock = lock.readLock();
writeLock = lock.writeLock();
store = new HashMap();
}
public void create(Transaction t){
if(t.getParent_id() !=null)
{
Transaction parent = get(t.getParent_id());
if(parent == null)
throw new RuntimeException(" Invalid parent id . id not exist in system");
}
writeLock.lock();
try
{
store.put(t.getId(),t);
}
finally
{
writeLock.unlock();
}
}
public Transaction get(Long id) {
readLock.lock();
try
{
return store.get(id);
}
finally
{
readLock.unlock();
}
}
}
Model Class :

package com.javaroots.model;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.annotate.JsonIgnoreProperties;
@JsonIgnoreProperties(ignoreUnknown=true)
public class Transaction {
private Long id ;
private Long parent_id ;
private String type ;
private Double amount ;
public Transaction(){};
public Transaction(Transaction t)
{
this.id = t.id ;
this.parent_id = t.parent_id;
this.type = t.type ;
this.amount = t.amount ;
}
@JsonIgnore
public Long getId() {
return id;
}
@JsonIgnore
public void setId(Long id) {
this.id = id;
}
public Long getParent_id() {
return parent_id;
}
public void setParent_id(Long parent_id) {
this.parent_id = parent_id;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public Double getAmount() {
return amount;
}
public void setAmount(Double amount) {
this.amount = amount;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Transaction other = (Transaction) obj;
if (id == null) {
if (other.id != null)
return false;
} else if (!id.equals(other.id))
return false;
return true;
}
}
Now following is our Rest Service class :

package com.javaroots.services.rest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.javaroots.dao.TransferDAO;
import com.javaroots.model.Transaction;
@Singleton
@Path("transactionservice/")
public class TransactionService {
private TransferDAO transferDAO ;
@Inject
public TransactionService(TransferDAO transferDAO)
{
this.transferDAO = transferDAO ;
}
@PUT
@Path("transaction/{transaction_id}")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public Response createTransaction(@PathParam("transaction_id")Long transactionId , Transaction entity) {
entity.setId(transactionId);
transferDAO.create(entity);
Map map = new HashMap();
map.put("status","OK");
return Response.status(Status.OK).entity(map).build();
}
@GET
@Path("transaction/{transaction_id}")
@Produces(MediaType.APPLICATION_JSON)
public Response getByType(@PathParam("transaction_id")Long transactionId) {
Transaction toRet = transferDAO.get(transactionId);
return Response.status(Status.OK).entity(toRet).build();
}
}
Now we bind this together using google Guice's ServletContextListener . To enable json support , you need to bind JacksonJsonProvider as well .

package com.javaroots.listeners;
import org.apache.log4j.Logger;
import org.codehaus.jackson.jaxrs.JacksonJsonProvider;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Singleton;
import com.google.inject.servlet.GuiceServletContextListener;
import com.javaroots.dao.TransferDAO;
import com.javaroots.dao.impl.TransferDAOMemoryImpl;
import com.javaroots.exception.RestExceptionMapper;
import com.javaroots.services.rest.TransactionService;
import com.sun.jersey.guice.JerseyServletModule;
import com.sun.jersey.guice.spi.container.servlet.GuiceContainer;
public class AppInitilizer extends GuiceServletContextListener {
Logger log = Logger.getLogger(AppInitilizer.class);
@Override
protected Injector getInjector() {

return Guice.createInjector(new JerseyServletModule() {
@Override
protected void configureServlets() {
bind(TransferDAO.class).to(TransferDAOMemoryImpl.class);
serve("/*").with(GuiceContainer.class);
// Configuring Jersey via Guice:
bind(TransactionService.class);
bind(RestExceptionMapper.class);
bind(JacksonJsonProvider.class).in(Singleton.class);
}
});
}
}
Now include this in web.xml .

<?xml version="1.0" encoding="ISO-8859-1" ?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<filter>
<filter-name>guiceFilter</filter-name>
<filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>guiceFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<listener>
<listener-class>com.javaroots.listeners.AppInitilizer</listener-class>
</listener>
</web-app>
Now you can access service at localhost:8080/{contextpath}/transactionservice Post Comments And Suggestions !!!

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