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
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.1</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>demo</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>
</project>
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, Integer> {
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操作，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
(?, ?, ?, ?)
当没有涉及主键的操作后，会直接调用insert操作。
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操作，没有变化不再进行操作，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
(?, ?, ?, ?)