SpringBoot整合jpa

一、Spring boot jpa 简介

Jpa（Java Persistence API）是Sun官方提出的Java持久化规范。它为Java开发人员提供了一种对象/关系映射（ORM）工具来管理Java应用中的关系数据。它的出现是为了简化现有的持久化开发工作和整合ORM技术。Spring Boot Jpa 是 Spring 基于 ORM 框架、Jpa 规范的基础上封装的一套 Jpa 应用框架，提供了包括增删改查等在内的常用功能。（封装好了，可以直接调用）

二、Springboot中 Jpa的基本使用

1.创建Springboot项目，导入依赖

<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>4.0.0modelVersion>
    <groupId>com.zccgroupId>
    <artifactId>jpatestartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>jpatestname>
    <description>Demo project for Spring Bootdescription>


    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.3.7.RELEASEversion>
        <relativePath/> 
    parent>

    <properties>
        <java.version>1.8java.version>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8project.reporting.outputEncoding>
        <spring-boot.version>2.3.7.RELEASEspring-boot.version>
        <mysql-connector-java.version>8.0.23mysql-connector-java.version>
    properties>

    <dependencies>
    
        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-data-jpaartifactId>
        dependency>


        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>${mysql-connector-java.version}version>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-devtoolsartifactId>
            <scope>runtimescope>
            <optional>trueoptional>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-configuration-processorartifactId>
            <optional>trueoptional>
        dependency>
        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>

        dependency>


    dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-dependenciesartifactId>
                <version>${spring-boot.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.pluginsgroupId>
                <artifactId>maven-compiler-pluginartifactId>
                <version>3.8.1version>
                <configuration>
                    <source>1.8source>
                    <target>1.8target>
                    <encoding>UTF-8encoding>
                configuration>
            plugin>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
                <version>2.3.7.RELEASEversion>
            plugin>
        plugins>
    build>

project>

2.配置数据源和jpa

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/args_db?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf8&useSSL=false
    username: root
    password: 111111
  jpa:
    hibernate:          
      ddl-auto: update  # 更新或者创建数据表结构 之前提到过，如果数据库中没做表，
                          Jpa会我们创建 这个配置就是在没有表的时候创建，
                          实体类发生改变的话 会更新表结构          
    show-sql: true    # 配置在日志中打印出执行的 SQL 语句信息

3.编写实体类添加Jpa注解配置映射关系

通过jpa操作数据就需要将实体类和数据库建立联系

package com.zcc.jpatest.domain;

import lombok.Data;
import org.hibernate.annotations.GenericGenerator;

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

/**
 * @author zhouchen
 * @date 2021/09/14
 **/

@Data
@Entity
@Table(name ="admin") //与哪张表映射
//使用jpa的uuid自动生成主键id策略，此外还可使用底层数据库的主键自增策略
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class Admin implements Serializable {
    @Column(length = 32)
    private static final long serialVersionUID = -805053659777047779L;
    @Id
    @GeneratedValue(generator = "jpa-uuid")
    @Column(name = "id",length = 32)
    private String adminId;
    private String username;
    private String password;

}
``

4.编写一个接口来操作实体类对应的数据表

```java
/**
 * JpaRepository 泛型1 被操作的实体类 泛型2 主键属性的类型
 */
public interface AdminRepository extends JpaRepository<Admin,String> {
}

5.编写测试类测试

@SpringBootTest(classes = JpatestApplication.class)
@RunWith(SpringRunner.class)
public class Jpatest {

    @Autowired
    private AdminRepository adminRepository;

    @Test
    public void testAdd(){
        System.out.println("添加操作：");
        Admin admin = new Admin();

        admin.setUsername("1991hhh9");
        admin.setPassword("993336");
        adminRepository.save(admin);
        System.out.println(admin);
        System.out.println("添加成功");
    }

    @Test
    public void testFind(){
        Optional<Admin> optional = adminRepository.findById("2c96ba4b7be25e2c017be25e2f660000");
        if(optional.isPresent()){
            Admin aa = optional.get();
            System.out.println(aa);
        }

    }
}

参考链接：

https://www.cnblogs.com/ityouknow/p/5891443.html

https://juejin.cn/post/6844904084282015757