Spring REST Template 快速入門

本篇將使用Spring Boot發佈REST Service，使用Spring REST Template來調用服務

本篇代碼均已上傳到GITHUB，https://github.com/IloveZiHan/restfultemplate.git

介紹

我們之前都使用過HttpClient來發送HTTP請求，但我們很多時間都需要將HttpClient請求或者響應的數據轉換爲Java對象，HttpClient需要我們自己手動來解析。我們今天要介紹的Spring REST Template比HttpClient用起來更加方便簡潔。

背景

案例分爲兩個部分：

1. CRM_MANAGEMENT——後臺主要提供RESTFUL Service服務，因爲儘量使案例簡單，所以數據部分是直接使用內存中的列表來模擬
2. PORTAL——門戶，也就是前端系統，用來處理瀏覽器提交的請求，接收到用戶請求會使用Spring REST Template來提交RESTFUL Service請求

環境說明

• 本案例基於Maven構建，使用Spring Boot 2.x開發
• 可以選擇IDEA或者Eclipse導入案例運行

項目開發

CRM_DOMAIN實體

POM依賴

• pom.xml

  <?xml version="1.0" encoding="UTF-8"?>
  <project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"&gt;
  <parent>
  <artifactId>resttemplate_common</artifactId>
  <groupId>com.itheima</groupId>
  <version>0.0.1-SNAPSHOT</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>

  <artifactId>crm_domain</artifactId>
  <packaging>jar</packaging>

  </project>

• User實體類

  package com.itheima.crm.domain;

  public class User {

  private Integer id;     // id
  private String username; // 用戶名
  private String password; // 密碼
  
  public Integer getId() {
      return id;
  }
  
  public void setId(Integer id) {
      this.id = id;
  }
  
  public String getPassword() {
      return password;
  }
  
  public void setPassword(String password) {
      this.password = password;
  }
  
  public String getUsername() {
      return username;
  }
  
  public void setUsername(String username) {
      this.username = username;
  }
  
  public boolean matchUsernameAndPassword(String username, String password) {
      if(this.username.equals(username) && this.password.equals(password)) {
          return true;
      }
      else {
          return false;
      }
  }

  }

ResResult——封裝響應結果

package com.itheima.crm.domain;

/**
 * 響應結果
 */
public class ResResult {

    private Boolean success; // 是否操作成功
    private String message; // 消息

    public ResResult() {
    }

    public ResResult(Boolean success, String message) {
        this.success = success;
        this.message = message;
    }

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

CRM_MANAGEMENT後臺

POM依賴

• pom.xml

  <?xml version="1.0" encoding="UTF-8"?>
  <project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"&gt;

  <modelVersion>4.0.0</modelVersion>
  
  <artifactId>crm_management</artifactId>
  
  <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.0.1.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
  </parent>
  
  <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
  </properties>
  
  <dependencies>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
  
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-devtools</artifactId>
          <scope>runtime</scope>
      </dependency>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-test</artifactId>
          <scope>test</scope>
      </dependency>
  
      <dependency>
          <groupId>com.itheima</groupId>
          <artifactId>crm_domain</artifactId>
          <version>0.0.1-SNAPSHOT</version>
      </dependency>
  </dependencies>
  
  <build>
      <plugins>
          <plugin>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-maven-plugin</artifactId>
          </plugin>
      </plugins>
  </build>

  </project>

RESTFUL Service接口開發

package com.itheima.crm.webservice;

import com.itheima.crm.domain.ResResult;
import com.itheima.crm.domain.User ;
import com.itheima.crm.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/user")
public class UserRestService {

    @Autowired
    private UserService userService;

    /**
     * 註冊服務
     * @param user 用戶
     * @return
     */
    @RequestMapping(method = RequestMethod.POST)
    public ResResult regist(@RequestBody User user) {
        try {
            userService.regist(user);
            return new ResResult(true, "添加成功");
        } catch (Exception e) {
            e.printStackTrace();
            return new ResResult(false, "添加失敗");
        }
    }

    /**
     * 登錄服務
     * @param username 用戶名
     * @param password 密碼
     * @return
     */
    @RequestMapping(value = "/{username}/{password}", method = RequestMethod.GET)
    public User login(@PathVariable("username") String username, @PathVariable("password") String password) {
        try {
            return userService.login(username, password);
        } catch (Exception e) {
            return null;
        }
    }

    @RequestMapping(method = RequestMethod.GET)
    public List<User> findAll() {
        return userService.findAll();
    }
}

Service層開發

• UserService接口

  package com.itheima.crm.service;

  import com.itheima.crm.domain.User ;

  import java.util.List;

  public interface UserService {
  void regist(User user);

  User login(String username, String password);
  
  List<User> findAll();

  }

• UserServiceImpl實現類

  package com.itheima.crm.service;

  import com.itheima.crm.dao.UserDao;
  import com.itheima.crm.domain.User;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.stereotype.Service;

  import java.util.List;

  @Service
  public class UserServiceImpl implements UserService{

  @Autowired
  private UserDao userDao;
  
  @Override
  public void regist(User user) {
      userDao.save(user);
  }
  
  @Override
  public User login(String username, String password) {
      return userDao.findOne(username, password);
  }
  
  @Override
  public List<User> findAll() {
      return userDao.findAll();
  }

  }

DAO層開發

• UserDao接口

  package com.itheima.crm.dao;

  import com.itheima.crm.domain.User ;

  import java.util.List;

  public interface UserDao {
  /**

  • 保存用戶

  • @param user 用戶
    */
    void save(User user);

    User findOne(String username, String password);

    List<User> findAll();
    }

• UserDaoImpl實現類

  package com.itheima.crm.dao;

  import com.itheima.crm.domain.User;
  import org.springframework.stereotype.Repository;

  import java.util.ArrayList;
  import java.util.List;

  @Repository
  public class UserDaoImpl implements UserDao{

  private List<User> users = new ArrayList<>();
  
  @Override
  public void save(User user) {
      users.add(user);
  }
  
  @Override
  public User findOne(String username, String password) {
      User userTmp = new User();
      userTmp.setUsername(username);
      userTmp.setPassword(password);
  
      for(User user : users) {
          if(user.matchUsernameAndPassword(username, password)) {
              return user;
          }
      }
  
      return null;
  }
  
  @Override
  public List<User> findAll() {
      return users;
  }
  
  public UserDaoImpl() {
      // 添加一些測試的用戶
      User user1 = new User();
      user1.setId(1);
      user1.setUsername("zhangsan");
      user1.setPassword("0");
  
      User user2 = new User();
      user2.setId(2);
      user2.setUsername("lisi");
      user2.setPassword("0");
  
      User user3 = new User();
      user3.setId(3);
      user3.setUsername("wangwu");
      user3.setPassword("0");
  
      User user4 = new User();
      user4.setId(4);
      user4.setUsername("zhaoliu");
      user4.setPassword("0");
  
      users.add(user1);
      users.add(user2);
      users.add(user3);
      users.add(user4);
  }

  }

Spring Boot入口

• 配置文件(application.properties)

  server.port=9001
  server.servlet.context-path=/

• 入口

  package com.itheima.crm;

  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;

  @SpringBootApplication
  public class Application {

  public static void main(String[] args) {
      SpringApplication.run(Application.class, args);
  }

  }

RESTFUL Service接口調用URL

• 添加用戶
  Requsest URL: http://localhost:9001/user/ Request Method: POST
• 根據用戶名密碼查詢用戶
  Requsest URL: http://localhost:9001/user/用戶名/密碼 Request Method: GET
• 查詢所有用戶
  Requeset URL: http://localhost:9001/user/ Request Method: GET

PORTAL門戶

POM依賴

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <modelVersion>4.0.0</modelVersion>
    <artifactId>portal</artifactId>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28</version>
        </dependency><dependency>
            <groupId>com.itheima</groupId>
            <artifactId>crm_domain</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Controller開發

package com.itheima.portal.controller;

import com.itheima.crm.domain.ResResult;
import com.itheima.crm.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private RestTemplate restTemplate;

    private String USERSERVICE_URL = "http://localhost:9001/user";

    @RequestMapping("/login")
    public Map login(String username, String password) {
        // 構建要傳遞的參數
        Map<String, String> params = new HashMap<>();
        params.put("username", username);
        params.put("password", password);
        // 發送GET請求
        User user = restTemplate.getForObject(USERSERVICE_URL + "/{username}/{password}", User.class, params);
        Map<String, Object> result = new HashMap<>();
        if(user != null) {
             result.put("success", true);
        }
        else {
            result.put("success", false);
            result.put("message", "登錄失敗");
        }

        return result;
    }

    @RequestMapping("/regist")
    public ResResult login(@RequestBody  User user) throws IOException {
        // 使用REST Template發送POST請求
        return restTemplate.postForObject(USERSERVICE_URL + "/", user, ResResult.class);
    }
}

Spring Boot入口

• 配置文件(application.properties)

  server.port=9002
  server.servlet.context-path=/

• 入口

  package com.itheima.portal;

  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  import org.springframework.context.annotation.Bean;
  import org.springframework.web.client.RestTemplate;

  @SpringBootApplication
  public class Application {

  public static void main(String[] args) {
      SpringApplication.run(Application.class, args);
  }
  
  /**
   * 創建RestTemplate Bean
   */
  @Bean
  public RestTemplate restTemplate() {
      return new RestTemplate();
  }

  }

• 前端頁面

1. 導入jquery.js

2. login.html登錄頁面

   <!doctype html>
   <html lang="`">
   <head>
   <meta charset="UTF-8">
   <meta name="viewport"
   content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
   <meta http-equiv="X-UA-Compatible" content="ie=edge">
   <title>登錄</title>
   <script src="jquery-1.11.3.js"></script>
   </head>
   <body>
   <table class="table">
   <tr>
   <td>用戶名</td>
   <td><input type="text" id="username"></td>
   </tr>
   <tr>
   <td>密碼</td>
   <td><input type="text" id="password"></td>
   </tr>
   <tr>
   <td></td>
   <td>
   <button id="btn">登錄</button>
   <button id="btn1">註冊</button>
   </td>
   </tr>
   </table>

   <script type="text/javascript">
       $(function() {
          $('#btn').click(function() {
              $.get('user/login?username=' + $('#username').val() + '&password=' + $('#password').val(), function(data) {
                 if(!data.success) {
                     alert(data.message);
                 }
                 else {
                     window.location.href = "success.html";
                 }
              });
          });
   
           $('#btn1').click(function() {
               var user = {
                       username: $('#username').val(),
                       password: $('#password').val()
               };
               $.ajax({
                   type:'POST',
                   url:'user/regist',
                   dataType:"json",
                   contentType:"application/json",
                   data:JSON.stringify(user),
                   success:function(data){
                       if(!data.success) {
                           alert(data.message);
                       }
                       else {
                           alert("註冊成功！");
                       }
                   }
               });
           });
       });
   </script>

   </body>
   </html>

3. success.html登錄成功頁面

   <!DOCTYPE html>
   <html lang="en">
   <head>
   <meta charset="UTF-8">
   <title>登錄成功</title>
   </head>
   <body>
   <h1>登錄成功</h1>
   </body>
   </html>

總結

Spring REST Template比HttpClient更加快捷方便的調用RS服務，它自動封裝和解析Java對象。而且可以很方便的與Spring整合，快速注入Spring的bean對象。

注意

注意Jquery $.get、$.post、$.ajax的區別

• $.get(url, json對象)表示發送一個get請求，使用queryString的方式提交。url?username=tom...

• $.post(url, json對象)表示發送一個post請求，數據部分類似於提交表單。

• $.ajax可以選擇數據傳遞的格式、類型等。我們要將一個json串發送到spring mvc @RequestBody來接收需要使用$.ajax。下面是示例代碼

  $.ajax({
  type:'POST',
  url:'user/regist',
  dataType:"json",
  contentType:"application/json",
  data:JSON.stringify(user),
  success:function(data){
  if(!data.success) {
  alert(data.message);
  }
  else {
  alert("註冊成功！");
  }
  }
  });