上一篇我們講了spring boot 整合JdbcTemplate來進行數據的持久化，

這篇我們來說下怎麽通過spring boot 整合JPA來實現數據的持久化。

一、代碼實現　

1. 修改pom，引入依賴

     <!-- 引入jpa 依賴 -->
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-data-jpa</artifactId>
    
   
           </dependency>

2. 修改application.properties，配置相關信息

   #修改tomcat默認端口號
   server.port=8090
   #修改context path
   server.context-path=/test
   
   #配置數據源信息
   spring.datasource.driver-class-name=com.mysql.jdbc.Driver
   spring.datasource.url=jdbc:mysql://localhost:3306/test
   spring.datasource.username=root
   spring.datasource.password=root
   #配置jpa
   spring.jpa.hibernate.ddl-auto=update
   spring.jpa.show-sql=true
   spring.jackson.serialization.indent_output=true
    
   

3. 創建實體類

   package com.study.entity;
   
   import javax.persistence.Entity;
   import javax.persistence.GeneratedValue;
   import javax.persistence.GenerationType;
   import javax.persistence.Id;
   import javax.persistence.Table;
   
   @Entity
   @Table(name="t_user")
   public class User {
   
       @Id @GeneratedValue(strategy=GenerationType.AUTO)
       
    
   private Integer id;
       private String userName;
       private String password;
   
       public Integer getId() {
           return id;
       }
   
       public void setId(Integer id) {
           this.id = id;
       }
   
       public String getUserName() {
           return userName;
       }
   
       public void setUserName(String userName) {
           this.userName = userName;
       }
   
       public String getPassword() {
           return password;
       }
   
       public void setPassword(String password) {
           this.password = password;
       }
   
   }

4. 創建repository接口並繼承CrudRepository

   package com.study.repository;
   
   import org.springframework.data.jpa.repository.Query;
   import org.springframework.data.repository.CrudRepository;
   import org.springframework.data.repository.query.Param;
   
   import com.study.entity.User;
   
   /**
    * 註意：
    * 1.這裏這裏是interface，不是class
    * 
    * 2.CrudRepository裏面的泛型，第一個是實體類，第二個是主鍵的類型
    * 
    * 3.由於crudRepository 裏面已經有一些接口了，如deleteAll，findOne等， 我們直接調用即可
    * 
    * 4.當然，我們也可以根據自己的情況來實現自己的接口,如下面的getUser()方法，jpql語句和hql語句差不多
    * 
    * */
   public interface UserRepository extends CrudRepository<User, Integer> {
   
       /**
        * 我們這裏只需要寫接口，不需要寫實現，spring boot會幫忙自動實現
        * 
        * */
       
       @Query("from User where id =:id ")
       public User getUser(@Param("id") Integer id);
   }

5. 創建service
   1. 接口

      package com.study.service;
      
      import com.study.entity.User;
      
      
      public interface UserService {
          public User getUser(Integer id);
      }

   2. 實現

      package com.study.service.impl;
      
      import org.springframework.beans.factory.annotation.Autowired;
      import org.springframework.stereotype.Service;
      
      import com.study.entity.User;
      import com.study.repository.UserRepository;
      import com.study.service.UserService;
      
      @Service
      public class UserServiceImpl implements UserService {
      
          @Autowired
          UserRepository repository;
          
          @Override
          public User getUser(Integer id) {
              //有兩種方式：
              //1.調用crudRepository的接口
      //        return repository.findOne(id);
              //2.調用我們自己寫的接口
              return repository.getUser(id);
          }
      
          
      }

6. 創建controller

   package com.study.controller;
   
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.web.bind.annotation.PathVariable;
   import org.springframework.web.bind.annotation.RequestMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   import com.study.entity.User;
   import com.study.service.UserService;
   
   @RestController
   public class UserController {
       @Autowired
       UserService service;
       
       @RequestMapping("/getUser/{id}")
       public User getUser(@PathVariable("id") Integer id){
           
           return service.getUser(id);
       }
   }

7. 測試，頁面以json格式顯示數據庫值

二、知識點引申

關於Repository知識點，可以去看下下面這篇文章

https://segmentfault.com/a/1190000012346333

spring boot 系列之四：spring boot 整合JPA