JPA实战之save

JPA实战之save

前言：之前一直都是直接使用JPA没有想过它内部封装的sql语言，然后看到了一篇文章 JPA踩坑系列之save方法，才发现这个框架并不好用。

验证save()的使用

pom文件

	4.0.0
	
		org.springframework.boot
		spring-boot-starter-parent
		2.6.1
		 
	
	com.example
	demo
	0.0.1-SNAPSHOT
	demo
	demo
	
		11
	
	
		
			org.springframework.boot
			spring-boot-starter-data-jpa
		

		
			mysql
			mysql-connector-java
			runtime
		
		
			org.projectlombok
			lombok
			true
		
		
			org.springframework.boot
			spring-boot-starter-test
			test
		
	

	
		
			
				org.springframework.boot
				spring-boot-maven-plugin
				
					
						
							org.projectlombok
							lombok
						
					
				
			
		
	

yml文件

spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/springboot_db?useUnicode=true&characterEncoding=UTF-8&useSSL=false
    driverClassName: com.mysql.cj.jdbc.Driver
    username: root
    password: root1234
  jpa:
    show-sql: true 
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
    hibernate:
      use-new-id-generator-mappings: false
    properties:
      hibernate.format_sql: true

show-sql: true 可以展示调用过程中的sql语句。

create table user
(
    user_id   varchar(20) null,
    enabled   tinyint(1)  not null,
    id        int auto_increment
        primary key,
    role_code varchar(50) not null,
    name      varchar(10) null,
    constraint dealer_id_role_code_idx
        unique (user_id, role_code)
)
    charset = utf8;

项目结构

user文件

package com.example.demo.entity;

import lombok.*;

import javax.persistence.*;
import java.io.Serializable;

@Builder
@NoArgsConstructor
@AllArgsConstructor
@Entity
@Getter
@Setter
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @Column(name = "user_id", length = 50, nullable = false)
    private String userId;

    @Column(name = "enabled", length = 1, nullable = false)
    private Boolean enabled;

    @Column(name = "role_code", length = 50, nullable = false)
    private String roleCode;

    private String name;

}

UserRepository文件

package com.example.demo.repository;

import com.example.demo.entity.User;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
@ComponentScan
public interface UserRepository extends JpaRepository {

    User findByUserIdAndRoleCode(String userID, String roleCode);
}

UserService文件

package com.example.demo.service;

import com.example.demo.entity.User;
import com.example.demo.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public int addUser(String userId) {
        User user = User.builder()
                .id(45747)
                .userId(userId)
                .enabled(false)
                .roleCode("Sup")
                .name("haha").build();
        return userRepository.save(user).getId();
    }
}

调用的mysql语句

Hibernate: 
    select
        user0_.id as id1_0_0_,
        user0_.enabled as enabled2_0_0_,
        user0_.name as name3_0_0_,
        user0_.role_code as role_cod4_0_0_,
        user0_.user_id as user_id5_0_0_ 
    from
        user user0_ 
    where
        user0_.id=?
Hibernate: 
    insert 
    into
        user
        (enabled, name, role_code, user_id) 
    values
        (?, ?, ?, ?)

因为创建user对象的时候涉及到了主键id，所以在save之前会进行一次select *** 作，以主键id为依据。

UserService文件

 public int addUser(String userId) {
        User user = User.builder()
                .userId(userId)
                .enabled(false)
                .roleCode("Sup")
                .name("haha").build();
        return userRepository.save(user).getId();
    }

调用的mysql语句

Hibernate: 
    insert 
    into
        user
        (enabled, name, role_code, user_id) 
    values
        (?, ?, ?, ?)

当没有涉及主键的 *** 作后，会直接调用insert *** 作。

UserService文件

 public int addUser(String userId) {
    User user = userRepository.findByUserIdAndRoleCode(userId,"Sup");
        user.setEnabled(true);
        return userRepository.save(user).getId();
    }

调用的mysql语句

Hibernate: 
    select
        user0_.id as id1_0_,
        user0_.enabled as enabled2_0_,
        user0_.name as name3_0_,
        user0_.role_code as role_cod4_0_,
        user0_.user_id as user_id5_0_ 
    from
        user user0_ 
    where
        user0_.user_id=? 
        and user0_.role_code=?
Hibernate: 
    select
        user0_.id as id1_0_0_,
        user0_.enabled as enabled2_0_0_,
        user0_.name as name3_0_0_,
        user0_.role_code as role_cod4_0_0_,
        user0_.user_id as user_id5_0_0_ 
    from
        user user0_ 
    where
        user0_.id=?
Hibernate: 
    update
        user 
    set
        enabled=?,
        name=?,
        role_code=?,
        user_id=? 
    where
        id=?

会按照查询条件先查一遍，然后再根据主键进行查找，发现值发生变化后，再进行update *** 作，没有变化不再进行 *** 作，如下所示。
UserService文件

 public int addUser(String userId) {
    User user = userRepository.findByUserIdAndRoleCode(userId,"Sup");
        user.setEnabled(false);
        return userRepository.save(user).getId();
    }

调用的mysql语句

Hibernate: 
    select
        user0_.id as id1_0_,
        user0_.enabled as enabled2_0_,
        user0_.name as name3_0_,
        user0_.role_code as role_cod4_0_,
        user0_.user_id as user_id5_0_ 
    from
        user user0_ 
    where
        user0_.user_id=? 
        and user0_.role_code=?
Hibernate: 
    select
        user0_.id as id1_0_0_,
        user0_.enabled as enabled2_0_0_,
        user0_.name as name3_0_0_,
        user0_.role_code as role_cod4_0_0_,
        user0_.user_id as user_id5_0_0_ 
    from
        user user0_ 
    where
        user0_.id=?

当给方法加上事务的注解(@Transactional)后，
UserService文件

@Transactional
 public int addUser(String userId) {
    User user = userRepository.findByUserIdAndRoleCode(userId,"Sup");
        user.setEnabled(false);
        return userRepository.save(user).getId();
    }

调用的mysql如下：

Hibernate: 
    select
        user0_.id as id1_0_,
        user0_.enabled as enabled2_0_,
        user0_.name as name3_0_,
        user0_.role_code as role_cod4_0_,
        user0_.user_id as user_id5_0_ 
    from
        user user0_ 
    where
        user0_.user_id=? 
        and user0_.role_code=?

但是当加上事物注解@Transactional，save前没有查询的话还是会先调用select语句
UserService文件

@Transactional
    public int addUser(String userId) {
    User user = User.builder()
                .id(123)
                .userId(userId)
                .enabled(false)
                .roleCode("Sup")
                .name("haha").build();
    return userRepository.save(user).getId();
    }

调用的mysql如下：

Hibernate: 
select
        user0_.id as id1_0_0_,
        user0_.enabled as enabled2_0_0_,
        user0_.name as name3_0_0_,
        user0_.role_code as role_cod4_0_0_,
        user0_.user_id as user_id5_0_0_ 
    from
        user user0_ 
    where
        user0_.id=?
Hibernate: 
    insert 
    into
        user
        (enabled, name, role_code, user_id) 
    values
        (?, ?, ?, ?)