springboot之整合JPA

接下来具体看看是怎么弄的。

1、新建一个springboot项目，选择web、data jdbc、data jpa、mysql driver。

2、建立以下目录及结构：

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>2.2.4.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>

3、在application.yml中配置连接数据库和jpa相关配置

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

4、新建一个entity包，新建实体类User.java

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;
    }
}

5、新建一个repository包，新建一个UserRepository.java

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> {
}

6、新建一个controller包，新建一个UserController.java

经过上述配置之后，我们就可以直接利用UserRepository中的一些方法进行数据库的操作啦，是不是很方便。

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;
    }

}

7、启动服务器

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