引言

在此之前，我们实现了第一个Rest application，通过分析她，我们了解了 Rest 程序的基本要素；这里，我们将会对第一个 Rest application 的功能进行扩充（实现 CRUD）。为了简化流程，我们依然采用文件的方式来模拟数据库操作。

第二个 Rest application

User

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 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

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

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>";   }}

WebServiceTester（Write test client ourselves）

Jersey允许我们自己实现测试类（Web Service Client）

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 );   }}

在Eclipse里面，选中 WebServiceTester，右键 -> run as Java application, 我们会在 console 里面看到一下输出

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

Rest verbs

现在，我们再来分析一下 Rest verbs，通过一下的表格我们能够更好地理解他们...

S.N.	HTTP Method, URI and Operation
1	GET http://localhost:8080/UserManagement/rest/UserService/users 获取 users 列表 (只读的)
2	GET http://localhost:8080/UserManagement/rest/UserService/users/1 获取 id=1 的user (只读的)
3	PUT http://localhost:8080/UserManagement/rest/UserService/users/2 插入 id =2 的 user (幂等的)
4	POST http://localhost:8080/UserManagement/rest/UserService/users/2 更新 id=2 的 user (N/A)
5	DELETE http://localhost:8080/UserManagement/rest/UserService/users/1 删除 id=1 的 user (幂等的)
6	OPTIONS http://localhost:8080/UserManagement/rest/UserService/users 列出 service 上面的所有 operations (Read Only)
7	HEAD http://localhost:8080/UserManagement/rest/UserService/users 返回 HTTP HEAD (Read Only)

注：从URI 中，我们不容易看出来究竟要执行 Rest service 的那个operation，operation需要体现以Class.Method的形式体现出来。

Rest之路 -- 从第二个Rest application里面分析 Rest 方法

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