ReST Web Service Implementation step by step.

www.javabykiran.com

Below are steps should be followed to make simple application for REST full Web service implementation.

First create server (Host web service) -- Create web application [Web Project in eclipse]

Add below Jars

Web.xml

<web-app>
<display-name>Archetype Created Web Application</display-name>
<!--  Auto scan REST service  -->
<context-param>
<param-name>resteasy.scan</param-name>
<param-value>true</param-value>
</context-param>
<servlet>
<servlet-name>resteasy-servlet</servlet-name>
<servlet-class>
org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>resteasy-servlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>

Create Model Class

import java.io.Serializable;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "user")
public class User implements Serializable {

private static final long serialVersionUID = 1L;

@XmlAttribute(name = "id" )
private int id;

@XmlElement(name = "firstName")
private String firstName;

@XmlElement(name = "lastName")
private String lastName;

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getFirstName() {
return firstName;
}

public void setFirstName(String firstName) {
this.firstName = firstName;
}

public String getLastName() {
return lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

}

Create Service Class

import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;

@Path("/user-management")
public class UserManagementModule {
@GET
@Path("/users")
public Response getAllUsers() {
String result = "First demo ";
System.out.println(result);
return Response.status(200).entity(result).build();
}

@GET
@Path("/users/{id}")
public Response getUserById(@PathParam("id")
Integer id) {
String result = "<user id=\"10\"><firstName>demo</firstName>"
+ "<lastName>user</lastName></user>";
return Response.status(200).entity(result).build();

}

/*
* @GET @Path("retrieve/{uuid}") public Response
* retrieveSomething(@PathParam("uuid") String uuid) { if(uuid == null ||
* uuid.trim().length() == 0) { return Response.serverError().entity("UUID
* cannot be blank").build(); } // Entity entity = service.getById(uuid);
* if(entity == null) { return
* Response.status(Response.Status.NOT_FOUND).entity("Entity not found for
* UUID: " + uuid).build(); } String json = //convert entity to json return
* Response.ok(json, MediaType.APPLICATION_JSON).build(); }
*/
@POST
@Path("/users123")
public Response createUser(String dd) {
System.out.println(dd);
String result = "<user id=\"10\"><firstName>demo</firstName><lastName>user</lastName></user>";
return Response.status(200).entity(result).build();

}

/*@Path("/hello")
public class Hello {

@POST
@Produces(MediaType.APPLICATION_ATOM_XML)
@Consumes(MediaType.MULTIPART_FORM_DATA)
public JSONObject sayPlainTextHello(JSONObject inputJsonObj)
throws Exception {

String input = (String) inputJsonObj.get("input");
String output = "The input you sent is :" + input;
JSONObject outputJsonObj = new JSONObject();
outputJsonObj.put("output", output);

return outputJsonObj;
}
}
*/
}

Client Code not to be deployed on server

import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import com.howtodoinjava.model.User;

public class DemoHttpRESTfulClient
{
public static void main(String[] args) throws Exception
{
//Demo Get request
//demoGetRESTAPI();

//Demo Post request
demoPostRESTAPI();
}


public static void demoGetRESTAPI() throws Exception
{
DefaultHttpClient httpClient = new DefaultHttpClient();
try
{
//Define a HttpGet request; You can choose between HttpPost, HttpDelete or HttpPut also.
//Choice depends on type of method you will be invoking.
//HttpGet getRequest = new HttpGet("http://localhost:8090/RestSer/user-management/users/10");
//HttpGet getRequest = new HttpGet("http://localhost:8090/RestSer/user-management-service/user1");
HttpGet getRequest = new HttpGet("http://localhost:8090/RestSer/user-management-service/user2XML");

//Set the API media type in http accept header
getRequest.addHeader("accept", "application/xml");

//Send the request; It will immediately return the response in HttpResponse object
HttpResponse response = httpClient.execute(getRequest);

//verify the valid error code first
int statusCode = response.getStatusLine().getStatusCode();
if (statusCode != 200)
{
throw new RuntimeException("Failed with HTTP error code : " + statusCode);
}

//Now pull back the response object
HttpEntity httpEntity = response.getEntity();
String apiOutput = EntityUtils.toString(httpEntity);

//Lets see what we got from API
System.out.println(apiOutput); //<user id="10"><firstName>demo</firstName><lastName>user</lastName></user>

//In realtime programming, you will need to convert this http response to some java object to re-use it.
//Lets see how to jaxb unmarshal the api response content
JAXBContext jaxbContext = JAXBContext.newInstance(User.class);
       Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
       User user = (User) jaxbUnmarshaller.unmarshal(new StringReader(apiOutput));
     
     
     
     
     
       //Verify the populated object
       System.out.println(user.getId());
       System.out.println(user.getFirstName());
       System.out.println(user.getLastName());
}
finally
{
//Important: Close the connect
httpClient.getConnectionManager().shutdown();
}
}

public static void demoPostRESTAPI() throws Exception
{
DefaultHttpClient httpClient = new DefaultHttpClient();

User user = new User();
user.setId(100);
user.setFirstName("jbk");
user.setLastName("javabykiran");

StringWriter writer = new StringWriter();
JAXBContext jaxbContext = JAXBContext.newInstance(User.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
        jaxbMarshaller.marshal(user, writer);
     
try
{
//Define a postRequest request
HttpPost postRequest = new HttpPost("http://localhost:8090/RestSer/user-management/users123");

//Set the API media type in http content-type header
postRequest.addHeader("content-type", "application/xml");

//Set the request post body
StringEntity userEntity = new StringEntity(writer.getBuffer().toString());
postRequest.setEntity(userEntity);

//Send the request; It will immediately return the response in HttpResponse object if any
HttpResponse response = httpClient.execute(postRequest);

//verify the valid error code first
int statusCode = response.getStatusLine().getStatusCode();
if (statusCode != 200)
{
throw new RuntimeException("Failed with HTTP error code : " + statusCode);
}
}
finally
{
//Important: Close the connect
httpClient.getConnectionManager().shutdown();
}
}

public static void demoPostJsonRESTAPI() throws Exception
{/*
DefaultHttpClient httpClient = new DefaultHttpClient();

User user = new User();
user.setId(100);
user.setFirstName("jbk");
user.setLastName("javabykiran");

StringWriter writer = new StringWriter();
JAXBContext jaxbContext = JAXBContext.newInstance(User.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
        jaxbMarshaller.marshal(user, writer);
     
try
{
 ClientConfig config = new DefaultClientConfig();
 Client client = Client.create(config);
 client.addFilter(new LoggingFilter());
 WebResource service = client.resource(getBaseURI());
 JSONObject inputJsonObj = new JSONObject();
 inputJsonObj.put("input", "Value");
 System.out.println(service.path("rest").path("hello").accept(MediaType.APPLICATION_JSON).post(JSONObject.class, inputJsonObj));}
finally
{
//Important: Close the connect
httpClient.getConnectionManager().shutdown();
}*/
}


}