RESTful Web Services - Methods

As we have discussed in the earlier chapters that RESTful Web Service uses a lot of HTTP verbs to determine the operation to be carried out on the specified resource(s). The following table states the examples of the most commonly used HTTP Verbs.

Sr.No.	HTTP Method, URI and Operation
1	GET http://localhost:8080/UserManagement/rest/UserService/users Gets the list of users. (Read Only)
2	GET http://localhost:8080/UserManagement/rest/UserService/users/1 Gets the User of Id 1 (Read Only)
3	PUT http://localhost:8080/UserManagement/rest/UserService/users/2 Inserts User with Id 2 (Idempotent)
4	POST http://localhost:8080/UserManagement/rest/UserService/users/2 Updates the User with Id 2 (N/A)
5	DELETE http://localhost:8080/UserManagement/rest/UserService/users/1 Deletes the User with Id 1 (Idempotent)
6	OPTIONS http://localhost:8080/UserManagement/rest/UserService/users Lists out the supported operations in a web service. (Read Only)
7	HEAD http://localhost:8080/UserManagement/rest/UserService/users Returns the HTTP Header only, no Body. (Read Only)

The following points are to be considered.

• GET operations are read only and are safe.
• PUT and DELETE operations are idempotent, which means their result will always be the same, no matter how many times these operations are invoked.
• PUT and POST operation are nearly the same with the difference lying only in the result where the PUT operation is idempotent and POST operation can cause a different result.

Example

Let us update an Example created in the RESTful Web Services - First Application chapter to create a Web service which can perform CRUD (Create, Read, Update, Delete) operations. For simplicity, we have used a file I/O to replace Database operations.
Let us update the User.java, UserDao.java and UserService.java files under the com.tutorialspoint package.

User.java

package com.tutorialspoint; 

import java.io.Serializable;  
import javax.xml.bind.annotation.XmlElement; 
import javax.xml.bind.annotation.XmlRootElement; 
@XmlRootElement(name = "user") 

public class User implements Serializable {  
   private static final long serialVersionUID = 1L; 
   private int id; 
   private String name; 
   private String profession;  
   public User(){}  
   
   public User(int id, String name, String profession){ 
      this.id = id; 
      this.name = name; 
      this.profession = profession; 
   }  
    
   public int getId() {
      return id; 
   } 
   @XmlElement 
   public void setId(int id) { 
      this.id = id; 
   } 
   public String getName() { 
      return name; 
   } 
   @XmlElement 
      public void setName(String name) { 
      this.name = name; 
   } 
   public String getProfession() { 
      return profession; 
   } 
   @XmlElement 
   public void setProfession(String profession) { 
      this.profession = profession; 
   }   
   @Override 
   public boolean equals(Object object){ 
      if(object == null){ 
         return false; 
      }else if(!(object instanceof User)){ 
         return false; 
      }else { 
         User user = (User)object; 
         if(id == user.getId() 
            && name.equals(user.getName()) 
            && profession.equals(user.getProfession())){ 
               return true; 
         }
      } 
      return false; 
   }  
} 

UserDao.java

package com.tutorialspoint;  

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.util.ArrayList; 
import java.util.List;  

public class UserDao { 
   public List<User> getAllUsers(){ 
      List<User> userList = null; 
      try { 
         File file = new File("Users.dat"); 
         if (!file.exists()) { 
            User user = new User(1, "Mahesh", "Teacher"); 
            userList = new ArrayList<User>(); 
            userList.add(user); 
            saveUserList(userList);   
         } 
         else{ 
            FileInputStream fis = new FileInputStream(file); 
            ObjectInputStream ois = new ObjectInputStream(fis); 
            userList = (List<User>) ois.readObject(); 
            ois.close(); 
         }
      } catch (IOException e) { 
         e.printStackTrace(); 
      } catch (ClassNotFoundException e) { 
         e.printStackTrace(); 
      }   
      return userList; 
   }  
   public User getUser(int id){ 
      List<User> users = getAllUsers();  
      for(User user: users){ 
         if(user.getId() == id){ 
            return user; 
         } 
      } 
      return null; 
   }  
   public int addUser(User pUser){ 
      List<User> userList = getAllUsers(); 
      boolean userExists = false; 
      for(User user: userList){ 
         if(user.getId() == pUser.getId()){ 
            userExists = true; 
            break; 
         } 
      }   
      if(!userExists){ 
         userList.add(pUser); 
         saveUserList(userList); 
         return 1; 
      } 
      return 0; 
   }
   public int updateUser(User pUser){ 
      List<User> userList = getAllUsers();  
      for(User user: userList){ 
         if(user.getId() == pUser.getId()){ 
            int index = userList.indexOf(user);    
            userList.set(index, pUser); 
            saveUserList(userList); 
            return 1; 
         } 
      }   
      return 0; 
   }  
   public int deleteUser(int id){ 
      List<User> userList = getAllUsers();  
      for(User user: userList){ 
         if(user.getId() == id){ 
            int index = userList.indexOf(user);    
            userList.remove(index); 
            saveUserList(userList); 
            return 1;    
         } 
      }   
      return 0; 
   }  
   private void saveUserList(List<User> userList){ 
      try { 
         File file = new File("Users.dat"); 
         FileOutputStream fos;  
         fos = new FileOutputStream(file);
         ObjectOutputStream oos = new ObjectOutputStream(fos);   
         oos.writeObject(userList); 
         oos.close(); 
      } catch (FileNotFoundException e) { 
         e.printStackTrace(); 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } 
   } 
}

UserService.java

package com.tutorialspoint;  

import java.io.IOException; 
import java.util.List;  
import javax.servlet.http.HttpServletResponse; 
import javax.ws.rs.Consumes; 
import javax.ws.rs.DELETE; 
import javax.ws.rs.FormParam; 
import javax.ws.rs.GET; 
import javax.ws.rs.OPTIONS; 
import javax.ws.rs.POST; 
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.Context; 
import javax.ws.rs.core.MediaType;  
@Path("/UserService") 

public class UserService { 
  
   UserDao userDao = new UserDao(); 
   private static final String SUCCESS_RESULT = "<result>success</result>"; 
   private static final String FAILURE_RESULT = "<result>failure</result>";  
   @GET 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   public List<User> getUsers(){ 
      return userDao.getAllUsers(); 
   }  
   @GET 
   @Path("/users/{userid}") 
   @Produces(MediaType.APPLICATION_XML) 
   public User getUser(@PathParam("userid") int userid){ 
      return userDao.getUser(userid); 
   }  
   @PUT 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   @Consumes(MediaType.APPLICATION_FORM_URLENCODED) 
   public String createUser(@FormParam("id") int id, 
      @FormParam("name") String name, 
      @FormParam("profession") String profession, 
      @Context HttpServletResponse servletResponse) throws IOException{ 
      User user = new User(id, name, profession); 
      int result = userDao.addUser(user); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   }  
   @POST 
   @Path("/users")  
   @Produces(MediaType.APPLICATION_XML)
   @Consumes(MediaType.APPLICATION_FORM_URLENCODED) 
   public String updateUser(@FormParam("id") int id, 
      @FormParam("name") String name, 
      @FormParam("profession") String profession, 
      @Context HttpServletResponse servletResponse) throws IOException{ 
      User user = new User(id, name, profession); 
      int result = userDao.updateUser(user); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   }  
   @DELETE 
   @Path("/users/{userid}") 
   @Produces(MediaType.APPLICATION_XML) 
   public String deleteUser(@PathParam("userid") int userid){ 
      int result = userDao.deleteUser(userid); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   }  
   @OPTIONS 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   public String getSupportedOperations(){ 
      return "<operations>GET, PUT, POST, DELETE</operations>"; 
   } 
}

Now using Eclipse, export your application as a WAR File and deploy the same in Tomcat. To create a WAR file using eclipse, follow this path – File → export → Web → War File and finally select project UserManagement and the destination folder. To deploy a WAR file in Tomcat, place the UserManagement.war in the Tomcat Installation Directory → webapps directory and the start Tomcat.

Testing the Web Service

Jersey provides APIs to create a Web Service Client to test web services. We have created a sample test class WebServiceTester.java under the com.tutorialspoint package in the same project.

WebServiceTester.java

package com.tutorialspoint;  

import java.util.List; 
import javax.ws.rs.client.Client; 
import javax.ws.rs.client.ClientBuilder; 
import javax.ws.rs.client.Entity; 
import javax.ws.rs.core.Form; 
import javax.ws.rs.core.GenericType; 
import javax.ws.rs.core.MediaType;  

public class WebServiceTester  {  
   private Client client; 
   private String REST_SERVICE_URL = "
   http://localhost:8080/UserManagement/rest/UserService/users"; 
   private static final String SUCCESS_RESULT = "<result>success</result>"; 
   private static final String PASS = "pass"; 
   private static final String FAIL = "fail";  
   private void init(){ 
      this.client = ClientBuilder.newClient(); 
   }  
   public static void main(String[] args){ 
      WebServiceTester tester = new WebServiceTester(); 
      //initialize the tester 
      tester.init(); 
      //test get all users Web Service Method 
      tester.testGetAllUsers(); 
      //test get user Web Service Method  
      tester.testGetUser();
      //test update user Web Service Method 
      tester.testUpdateUser(); 
      //test add user Web Service Method 
      tester.testAddUser(); 
      //test delete user Web Service Method 
      tester.testDeleteUser(); 
   } 
   //Test: Get list of all users 
   //Test: Check if list is not empty 
   private void testGetAllUsers(){ 
      GenericType<List<User>> list = new GenericType<List<User>>() {}; 
      List<User> users = client 
         .target(REST_SERVICE_URL) 
         .request(MediaType.APPLICATION_XML) 
         .get(list); 
      String result = PASS; 
      if(users.isEmpty()){ 
         result = FAIL; 
      } 
      System.out.println("Test case name: testGetAllUsers, Result: " + result ); 
   } 
   //Test: Get User of id 1 
   //Test: Check if user is same as sample user 
   private void testGetUser(){ 
      User sampleUser = new User(); 
      sampleUser.setId(1);  
      User user = client 
         .target(REST_SERVICE_URL) 
         .path("/{userid}") 
         .resolveTemplate("userid", 1) 
         .request(MediaType.APPLICATION_XML) 
         .get(User.class); 
      String result = FAIL; 
      if(sampleUser != null && sampleUser.getId() == user.getId()){
         result = PASS; 
      } 
      System.out.println("Test case name: testGetUser, Result: " + result ); 
   } 
   //Test: Update User of id 1 
   //Test: Check if result is success XML. 
   private void testUpdateUser(){ 
      Form form = new Form(); 
      form.param("id", "1"); 
      form.param("name", "suresh"); 
      form.param("profession", "clerk");  
      String callResult = client 
         .target(REST_SERVICE_URL) 
         .request(MediaType.APPLICATION_XML) 
         .post(Entity.entity(form, 
         MediaType.APPLICATION_FORM_URLENCODED_TYPE), 
         String.class); 
      String result = PASS; 
      if(!SUCCESS_RESULT.equals(callResult)){ 
         result = FAIL; 
      }  
      System.out.println("Test case name: testUpdateUser, Result: " + result); 
   } 
   //Test: Add User of id 2 
   //Test: Check if result is success XML. 
   private void testAddUser(){ 
      Form form = new Form(); 
      form.param("id", "2"); 
      form.param("name", "naresh"); 
      form.param("profession", "clerk");  
      String callResult = client 
         .target(REST_SERVICE_URL) 
         .request(MediaType.APPLICATION_XML) 
         .put(Entity.entity(form, 
         MediaType.APPLICATION_FORM_URLENCODED_TYPE), 
         String.class); 
    
      String result = PASS; 
      if(!SUCCESS_RESULT.equals(callResult)){ 
         result = FAIL; 
      }  
      System.out.println("Test case name: testAddUser, Result: " + result ); 
   } 
   //Test: Delete User of id 2 
   //Test: Check if result is success XML. 
   private void testDeleteUser(){ 
      String callResult = client 
         .target(REST_SERVICE_URL) 
         .path("/{userid}") 
         .resolveTemplate("userid", 2) 
         .request(MediaType.APPLICATION_XML) 
         .delete(String.class);  
      String result = PASS; 
      if(!SUCCESS_RESULT.equals(callResult)){ 
         result = FAIL; 
      } 
      System.out.println("Test case name: testDeleteUser, Result: " + result); 
   } 
}

Now run the tester using Eclipse. Right click on the file and follow the option Run as → Java Application. You will see the following result in the Eclipse console −

Test case name: testGetAllUsers, Result: pass 
Test case name: testGetUser, Result: pass 
Test case name: testUpdateUser, Result: pass 
Test case name: testAddUser, Result: pass 
Test case name: testDeleteUser, Result: pass