RESTful Web服务 – 方法

正如我们所讨论的那样，RESTful Web服务会大量使用HTTP动词来确定对指定资源的操作。下表列出了HTTP动词的常见用法示例。

以下是需要考虑的重要点：

• GET操作是只读且安全的。

• PUT和DELETE操作是幂等的，这意味着无论调用这些操作多少次，其结果始终相同。

• PUT和POST操作几乎是相同的，不同之处仅在于PUT操作是幂等的，而POST操作可能会导致不同的结果。

示例

让我们更新RESTful Web服务 – 第一个应用程序教程中创建的示例，创建一个可以执行CRUD（Create、Read、Update、Delete）操作的Web服务。为简单起见，我们使用文件I/O来代替数据库操作。

更新com.tutorialspoint包下的 UserService.java 、 User.java 、 UserDao.java 文件。

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

将计算机领域的英文文章翻译成中文是一项有用的技能。上面这段HTML格式的代码讲述了一个Java程序，是一个用户类。该类有一个id，一个名字和一个职业，代表了一个用户的信息。此外，该类还有一些方法，例如getId()、getName()和getProfession()，它们可以获取相应的属性。此外，在equals()方法中还有一些逻辑来比较两个用户是否相等。

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 {

   // 获取所有用户列表
   public List<User> getAllUsers(){
      List<User> userList = null;
      try {
         File file = new File("Users.dat");
         // 如果数据文件不存在，则添加初始用户并保存，否则读取保存的用户列表
         if (!file.exists()) {
            User user = new User(1, "Mahesh", "Teacher"); // 初始用户
            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(); // 读取保存的用户列表
            ois.close();
         }
      } catch (IOException e) {
         e.printStackTrace();
      } catch (ClassNotFoundException e) {
         e.printStackTrace();
      }     
      return userList;
   }

   // 根据编号获取用户
   public User getUser(int id){
      List<User> users = getAllUsers();

      for(User user: users){
         if(user.getId() == id){
            return user; // 返回匹配的用户
         }
      }
      return null; // 没有匹配的用户返回 null
   }

   // 添加用户
   public int addUser(User pUser){
      List<User> userList = getAllUsers();
      boolean userExists = false;
      // 检查用户是否已存在
      for(User user: userList){
         if(user.getId() == pUser.getId()){
            userExists = true;
            break;
         }
      }     
      // 如果用户不存在，则添加该用户
      if(!userExists){
         userList.add(pUser);
         saveUserList(userList);
         return 1;
      }
      return 0;
   }

   // 更新用户
   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; // 如果没有匹配的用户，则更新失败
   }

   // 删除用户
   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; // 如果没有匹配的用户，则删除失败
   }

   // 保存用户列表到文件
   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); // 将用户列表保存到文件
         oos.close();
      } catch (FileNotFoundException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

UserService.java

package com.tutorialspoint;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;

public class WebServiceTester {

   private static final String BASE_URL = "http://localhost:8080/UserManagement/rest/UserService/";

   public static void main(String[] args) {
      try {
         testGetAllUsers();
         testGetUser();
         testCreateUser();
         testUpdateUser();
         testDeleteUser();
         testSupportedOperations();
      } catch (Exception e) {
         e.printStackTrace();
      }
   }

   private static void testGetAllUsers() throws IOException {
      URL url = new URL(BASE_URL + "users");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("GET");
      conn.setRequestProperty("Accept", "application/xml");

      if (conn.getResponseCode() != 200) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }

   private static void testGetUser() throws IOException {
      URL url = new URL(BASE_URL + "users/1");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("GET");
      conn.setRequestProperty("Accept", "application/xml");

      if (conn.getResponseCode() != 200) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }

   private static void testCreateUser() throws IOException {
      URL url = new URL(BASE_URL + "users");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setDoOutput(true);
      conn.setRequestMethod("POST");
      conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

      String input = "id=5&name;=John&profession;=Tester";

      conn.getOutputStream().write(input.getBytes());

      if (conn.getResponseCode() != HttpURLConnection.HTTP_CREATED) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }

   private static void testUpdateUser() throws IOException {
      URL url = new URL(BASE_URL + "users");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setDoOutput(true);
      conn.setRequestMethod("PUT");
      conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

      String input = "id=5&name;=John&profession;=Developer";

      conn.getOutputStream().write(input.getBytes());

      if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }

   private static void testDeleteUser() throws IOException {
      URL url = new URL(BASE_URL + "users/5");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("DELETE");

      if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }

   private static void testSupportedOperations() throws IOException {
      URL url = new URL(BASE_URL + "users");
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("OPTIONS");
      conn.setRequestProperty("Accept", "application/xml");

      if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
         throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
      }

      BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

      String output;
      System.out.println("Output from Server .... \n");
      while ((output = br.readLine()) != null) {
         System.out.println(output);
      }

      conn.disconnect();
   }
}

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)
         .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: 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)
         .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: 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 );
   }
}

现在在Eclipse中运行测试器。右键单击该文件，然后按照以下选项 **Run as – > Java Application ** 。您将在Eclipse控制台中看到以下结果−

测试用例名称：testGetAllUsers，结果：通过
测试用例名称：testGetUser，结果：通过
测试用例名称：testUpdateUser，结果：通过
测试用例名称：testAddUser，结果：通过
测试用例名称：testDeleteUser，结果：通过