Springboot整合使用JPA进行增删改查

ゝ一世哀愁。 2024-04-06 12:05 82阅读 0赞

## Springboot整合使用JPA进行增删改查 ##

### 一、添加maven依赖 ###

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

### 二、创建数据库表t\_user ###

![在这里插入图片描述][51b6191cec2f4ccf8f81ee552d5df013.png]

CREATE TABLE `t_user` (
      `id` bigint NOT NULL AUTO_INCREMENT,
      `username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '' COMMENT '用户',
      `password` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '密码',
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=131 DEFAULT CHARSET=utf8mb3;

### 三、yaml文件配置 ###

#MySql8.0
    spring:
      datasource:
        driverClassName: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/order_system?useSSL=false&characterEncoding=utf-8&useUnicode=true&serverTimezone=Asia/Shanghai
        username: root
        password: 123456
    
      #JPA配置
      jpa:
        hibernate:
          #更新或创建表结构
          ddl-auto: update
        #控制台显示sql
        show-sql: true

### 四、创建实体类TUser ###

import lombok.Getter;
    import lombok.Setter;
    import lombok.ToString;
    
    import javax.persistence.*;
    
    @Entity
    @Table(name = "t_user")
    @Setter
    @Getter
    @ToString
    public class TUser {
        
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)//配置主键的生成策略
        @Column(name = "id") //指定和表中id字段的映射关系
        private Integer id;
    
        @Column(name = "username") //指定和表中username字段的映射关系
        private String username;
    
        @Column(name = "password") //指定和表中password字段的映射关系
        private String password;
    
    }

### 五、编写DAO层`extends CrudRepository` ###

import com.example.domain.TUser;
    import org.springframework.data.repository.CrudRepository;
    
    @Repository
    public interface TUserRepository extends CrudRepository<TUser,Integer> {
        
        
    }

### 六、编写controller层测试增删改查 ###

#### 1、增加`save` ####

@RestController
    public class TUserController {
        
    
        @Autowired
        private TUserRepository tUserRepository;
    
        @PostMapping("/addTUser")
        public String addTUser(@RequestBody TUser tUser){
        
            tUserRepository.save(tUser);
            return "SUCCESS";
        }

**postman测试：**

![在这里插入图片描述][fb19bc4464354d1787cfd8d8ff8234a2.png]

#### 2、删除`deleteById` ####

@RestController
    public class TUserController {
        
    
        @Autowired
        private TUserRepository tUserRepository;
    
        @DeleteMapping("/deleteTUser")
        public String deleteTUser(Integer id) {
        
            tUserRepository.deleteById(id);
            return "SUCCESS";
        }
    }

**postman测试：**

![在这里插入图片描述][a8a3a9bdebf84149988c7bf916d2cfd7.png]

#### 3、查询`findById` ####

@RestController
    public class TUserController {
        
    
        @Autowired
        private TUserRepository tUserRepository;
    
        @GetMapping("/getUser")
        public Optional<TUser> getUser(Integer id) {
        
            return tUserRepository.findById(id);
        }
    }

**postman测试：**

![在这里插入图片描述][ae05d8a162fc489daea16d558e915b44.png]

#### 4、自定义查询 ####

JPA可以根据不同的查询条件在`DAO层接口中`自定义查询。  
比如：定义一个`根据id和username为查询条件`的方法。

**controller层调用：**

@RestController
    public class TUserController {
        
    
        @Autowired
        private TUserRepository tUserRepository;
    
        @GetMapping("/getTuser")
        public TUser getTuser(@RequestParam Integer id,@RequestParam String username){
        
          return   tUserRepository.findTUserByIdAndUsername(id,username);
        }
    }

**postman测试：**

![在这里插入图片描述][31af7e9eb3984d89b729d8e0ef721a9b.png]

#### 5、修改 ####

***注意：***

在使用JPA中，发现JPA实现了一些方法，如find，save等，但是没有update。如果想通过JPA进行修改，可以通过以下两种方式：

1.  使用@Query，编写nativeSQL，通过原生的SQLupdate。优点，可以自己定制，缺点，SQL语句繁琐，不灵活，不能实现动态更改某个属性。

***在DAO层接口定义update方法：***

***注意：***

①写update原生sql语句，与查询语句的注解不同，除了`@Query`，还需要两个额外注解 `@Modifying`和`@Transactional`

②SQL语句用了`具名参数`,在方法中用`@Param`注解与其映射

import org.springframework.data.jpa.repository.Modifying;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.data.repository.CrudRepository;
    import org.springframework.data.repository.query.Param;
    import org.springframework.transaction.annotation.Transactional;
    
    @Repository
    public interface TUserRepository extends CrudRepository<TUser, Integer> {
        
        @Modifying
        @Transactional
        @Query(value = "UPDATE T_USER SET USERNAME = :username WHERE ID = :id", nativeQuery = true)
        void updateTUser(@Param("username") String username, @Param("id") int id);
    }

***controller层调用：***

***注意：***

*调用update方法传入参数的顺序要和定义方法传入参数的顺序一致。*

@RestController
    public class TUserController {
        
    
        @Autowired
        private TUserRepository tUserRepository;
    
        @PutMapping("/updTUser")
        public String updTUser(@RequestParam String username,@RequestParam Integer id){
        
             tUserRepository.updateTUser(username,id);
             return "SUCCESS";
        }
    }

**postman测试：**  
![在这里插入图片描述][b2597872c15644bdad14ce9d50dddb36.png]

1.  其实save方法中JPA已经对update做了处理，save方法可以看做saveOrUpdate。

[51b6191cec2f4ccf8f81ee552d5df013.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/9a53fa9d12c1446890f4fb175892d8fb.png
[fb19bc4464354d1787cfd8d8ff8234a2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/e10c792041c94575aefbe604516bf196.png
[a8a3a9bdebf84149988c7bf916d2cfd7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/be265fcc49ea44999776d5aa41afa9e2.png
[ae05d8a162fc489daea16d558e915b44.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/7e7c81ce2b2c4a0c93d4118007f3637a.png
[31af7e9eb3984d89b729d8e0ef721a9b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/8f3603c3bc124a9cbc1c1290f193ff2c.png
[b2597872c15644bdad14ce9d50dddb36.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/64453598096049e68fedf63580f5d2b1.png