Jars Required:
1.
asm-all-3.3.1.jar
2.
commons-codec.jar
3.
commons-httpclient.jar
4.
commons-logging.jar
5.
jersey-bundle-1.14.jar
6.
json-simple.jar
Tools Required:
1.
Eclipse
2.
Any
webserver/application server
3. JDK 1.7
References:
http://rest.elkstein.org/
Restful service:
REST (Representational state Transfer) is an
architectural style which is based on WEB standards and the HTTP protocol.
It relies on a
a.
Stateless
b.
client-server
c.
Cacheable
communications protocol.
As a programming approach
REST is light weight alternative to web service (SOAP) and RPC.
Features:
1.
Data which is retrieved
from the server is known as resource.
2.
Resources identified
over the network by URI.
3.
Bounded by
standard protocol HTTP.
4.
It’s a stateless
and simple
5.
Request response represented
in JSON/XML/TEXT etc.
REST sample:
Server side implementation:
Class: WebServices.java
Using annotation
@Path (“/WebServices”) in below code we are just saying this is class needs to
looked up for the request http://localhost:8080/Restwebservice/webservice. Annotation @Get used for querying the
resource. A method level annotation @Path (“hello”) used to identify the resource
and URI for this http://localhost:8080/Restwebservice/webservice/hello. Annotation @Produces("application/json") used for specifying the response type.
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import
javax.ws.rs.QueryParam;
@Path("/webservice")
public class WebServices {
private static Map<String,
Employee> employees = new HashMap<String, Employee>();
@GET
@Path("/hello")
@Produces("application/json")
public List<Heloo>
hello() {
Map
hellomap = new HashMap();
Heloo
h = new Heloo();
h.setLname("Savadi");
h.setName("Prashant");
hellomap.put("1", h);
Heloo
h1 = new Heloo();
h1.setLname("Savadi");
h1.setName("Sushant");
hellomap.put("2", h1);
return new
ArrayList<Heloo>(hellomap.values());
}
@GET
@Path("/message")
@Produces("text/plain")
public String showMsg(@QueryParam("message") String message) {
return message;
}
@GET
@Path("/employees")
@Produces("application/xml")
public List<Employee>
listEmployees() {
return new
ArrayList<Employee>(employees.values());
}
@GET
@Path("/employee/{employeeid}")
@Produces("application/xml")
public Employee getEmployee(@PathParam("employeeid") String employeeId) {
return employees.get(employeeId);
}
@GET
@Path("/json/employees/")
@Produces("application/json")
public Map
listEmployeesJSON() {
return employees;
}
@GET
@Path("/json/employee/{employeeid}")
@Produces("application/json")
public Employee
getEmployeeJSON(@PathParam("employeeid") String employeeId) {
return employees.get(employeeId);
}
}
Class: Heloo.java
This is model
class used for returning the data.
import
javax.xml.bind.annotation.XmlElement;
import
javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement(name = "heloo")
public class Heloo {
private String name;
private String lname;
@XmlElement
public String getName() {
return name;
}
public void setName(String name)
{
this.name = name;
}
@XmlElement
public String getLname() {
return lname;
}
public void setLname(String
lname) {
this.lname = lname;
}
}
WEB.xml file entry for servlet
registration:
REST is implemented by jersey API. Need jersey
servlet entry in the server wheel.
<servlet>
<servlet-name>jersey-serlvet</servlet-name>
<servlet-class>
com.sun.jersey.spi.container.servlet.ServletContainer
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>jersey-serlvet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
Client:
Using below client we can access the resources from server (cleint/server architecture) using URI :http://localhost:9084/Rest/webservice/hello.
Here response us JSON format and JSON data can be handled by simple-Json API.
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import
org.json.simple.JSONArray;
import
org.json.simple.JSONObject;
import
org.json.simple.parser.JSONParser;
import
com.sun.jersey.api.client.Client;
import
com.sun.jersey.api.client.ClientResponse;
import
com.sun.jersey.api.client.WebResource;
public class RestWebServiceClient
{
/**
* @param args
*/
public static void main(String[] args)
{
RestWebServiceClient
restWebServiceClient = new RestWebServiceClient();
restWebServiceClient.sayHello();
//
restWebServiceClient.getJSONEmployees();
/*
*
restWebServiceClient.getMessage("Welcome");
* restWebServiceClient.getXMLEmployees();
* restWebServiceClient.getXMLEmployee(11111);
* restWebServiceClient.getJSONEmployees();
* restWebServiceClient.getJSONEmployee(11111);
*/
}
private void sayHello() {
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:9084/Rest/webservice/hello");
ClientResponse
response = webResource.accept("application/json")
.get(ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getResponse============");
Object
p = new
JSONParser().parse(output);
JSONObject
array = (JSONObject) p;
JSONArray
jarray = (JSONArray) array.get("heloo");
Heloo
h=null;
List
list = new ArrayList();
Iterator
it = jarray.iterator();
while (it.hasNext()) {
h=
new Heloo();
JSONObject
obj=((JSONObject) it.next());
System.out.println(obj.get("name"));
System.out.println(obj.get("lname"));
h.setName(obj.get("name")+"");
h.setLname(obj.get("lname")+"");
list.add(h);
}
System.out.println(list.toString());
}
catch (Exception e) {
e.printStackTrace();
}
}
private void getMessage(String
msg) {
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:8080/Restwebservice/webservice/message/"
+
msg);
ClientResponse
response = webResource.accept("text/plain").get(
ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getCResponse============");
System.out.println(output);
}
catch (Exception e) {
e.printStackTrace();
}
}
private void getXMLEmployees()
{
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:8080/Restwebservice/webservice/employees");
ClientResponse
response = webResource.accept("application/xml")
.get(ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getCResponse============");
System.out.println(output);
}
catch (Exception e) {
e.printStackTrace();
}
}
private void getXMLEmployee(int empid) {
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:8080/Restwebservice/webservice/employee/"
+
empid);
ClientResponse
response = webResource.accept("application/xml")
.get(ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getCResponse============");
System.out.println(output);
}
catch (Exception e) {
e.printStackTrace();
}
}
private void getJSONEmployees()
{
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:8080/Restwebservice/webservice/json/employees/");
ClientResponse
response = webResource.accept("application/json")
.get(ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getCResponse============");
System.out.println(output);
}
catch (Exception e) {
e.printStackTrace();
}
}
private void getJSONEmployee(int empid) {
try {
Client
client = Client.create();
WebResource
webResource = client
.resource("http://localhost:8080/Restwebservice/webservice/json/employee/"
+
empid);
ClientResponse
response = webResource.accept("application/json")
.get(ClientResponse.class);
if
(response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP
error code : "
+
response.getStatus());
}
String
output = response.getEntity(String.class);
System.out.println("\n============getCResponse============");
System.out.println(output);
}
catch (Exception e) {
e.printStackTrace();
}
}
}
