57.SpringBoot学习笔记--SpringData-整合SpringDataJPA

SpringData JPA 简介

参考：

Java Persistence API 2.0 FINAL 官方文档.pdf

整合 SpringData JPA

pom.xml

<?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>2.3.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>demo.yangxu</groupId>
    <artifactId>springboot-05-data-jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-05-data-jpa</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

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

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

JPA: ORM（Object Relational Mapping）

1、编写一个实体类（Bean）和数据表进行映射，并且配置好映射关系

demo.yangxu.springboot.entity.User

package demo.yangxu.springboot.entity;

import javax.persistence.*;

//使用JPA注解配置映射关系
@Entity //告诉JPA这是一个实体类（和数据表映射的类）
@Table(name = "tbl_user") //@Table来指定和哪个数据表对应;如果省略默认表名就是user；
public class User {
    
    @Id //这是一个主键
    @GeneratedValue(strategy = GenerationType.IDENTITY) //自增主键
    private Integer id;
    
    @Column(name = "last_name",length = 50) //这是和数据表对应的一个列
    private String lastName;
    
    @Column //省略默认列名就是属性名
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

2、编写一个 Dao 接口来操作实体类对应的数据表（Repository）

demo.yangxu.springboot.repository.UserRepository

package demo.yangxu.springboot.repository;

import demo.yangxu.springboot.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

//继承JpaRepository来完成对数据库的操作
public interface UserRepository extends JpaRepository<User,Integer> {
}

3、基本的配置 JpaProperties

application.yml

spring:
  datasource:
    url: jdbc:mysql://192.168.25.157/jpa
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    hibernate:
      #     更新或者创建数据表结构
      ddl-auto: update
    #    控制台显示SQL
    show-sql: true

4、编写 Controller 进行测试

demo.yangxu.springboot.controller.UserController

package demo.yangxu.springboot.controller;

import demo.yangxu.springboot.entity.User;
import demo.yangxu.springboot.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    UserRepository userRepository;

    @GetMapping("/user/{id}")
    public User getUserById(@PathVariable("id") Integer id){
        User user = userRepository.findById(id).orElse(null);
        return user;
    }

    @GetMapping("/user")
    public User insertUser(User user){
        User save = userRepository.save(user);
        return save;
    }
}

启动控制台后可以看到自动生成的建表语句：

Hibernate: create table tbl_user (id integer not null auto_increment, email varchar(255), last_name varchar(50), primary key (id)) engine=InnoDB

可以访问以下网址测试：

http://localhost:8080/user?lastName=AA&[email protected]
http://localhost:8080/user/1