springboot整合JPA过程解析

<?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>2.2.4.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>
  <groupId>com.gong</groupId>
  <artifactId>springbootjpa</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>springbootjpa</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-data-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>
      <version>5.1.41</version>
      <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>

spring:
 datasource:
  url: jdbc:mysql://192.168.124.22:3306/jpa
  username: root
  password: 123456
  driver-class-name: com.mysql.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

package com.gong.springbootjpa.entity;


import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

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；
@JsonIgnoreProperties(value = {"hibernateLazyInitializer","handler"})
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;
  }
}

package com.gong.springbootjpa.repository;

import com.gong.springbootjpa.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

//继承JpaRepository来完成对数据库的操作，在JdbcRepository中指定实体类，数据库中主键对应的java类型
public interface UserRepository extends JpaRepository<User,Integer> {
}

package com.gong.springbootjpa.controller;

import com.gong.springbootjpa.entity.User;
import com.gong.springbootjpa.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 getUser(@PathVariable("id") Integer id){
    User user = userRepository.getOne(id);
    return user;
  }

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

}