SpringBoot+Jpa+MySql学习

时间：2023-12-28 15:40:32

上一篇介绍了springboot简单整合mybatis的教程。这一篇是介绍springboot简单整合jpa的教程。

由于jpa的功能强大，后续会继续写关于jpa的介绍已经使用，本文只是简单介绍一下它与springboot的整合。

jpa不需要像mybatis一样创建表，首先给大家看一下application.properties文件代码，其中包含了jpa的配置和数据库配置，尤其注意一下spring.jpa.hibernate.ddl-auto属性，代码如下：

##端口号

server.port=8888

##数据库配置

##数据库地址

spring.datasource.url=jdbc:mysql://localhost:3306/test?characterEncoding=utf8&useSSL=false

##数据库用户名

spring.datasource.username=root

##数据库密码

spring.datasource.password=root

##数据库驱动

spring.datasource.driver-class-name=com.mysql.jdbc.Driver

##validate  加载hibernate时，验证创建数据库表结构

##create   每次加载hibernate，重新创建数据库表结构，这就是导致数据库表数据丢失的原因。

##create-drop        加载hibernate时创建，退出是删除表结构

##update                 加载hibernate自动更新数据库结构

##validate 启动时验证表的结构，不会创建表

##none  启动时不做任何操作

spring.jpa.hibernate.ddl-auto=create

##控制台打印sql

spring.jpa.show-sql=true

启动类application

package com.dalaoyang;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

public class SpringbootJpaApplication {

    public static void main(String[] args) {

        SpringApplication.run(SpringbootJpaApplication.class, args);

    }

}

pom文件大致和整合mybatis一样，只是把其中的mybatis改成了jpa，代码如下：

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.dalaoyang</groupId>

    <artifactId>springboot_jpa</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <packaging>jar</packaging>

    <name>springboot_jpa</name>

    <description>springboot_jpa</description>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>1.5.9.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

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

    </properties>

    <dependencies>

        <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>org.springframework.boot</groupId>

            <artifactId>spring-boot-devtools</artifactId>

            <scope>runtime</scope>

        </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>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

实体类city，其中@Table中的name对应数据库中表的名称

package com.dalaoyang.entity;

import javax.persistence.*;

/**

 * @author dalaoyang

 * @Description

 * @project springboot_learn

 * @package com.dalaoyang.Entity

 * @email 397600342@qq.com

 * @date 2018/4/7

 */

@Entity

@Table(name="city")

public class City {

    @Id

    @GeneratedValue(strategy=GenerationType.AUTO)

    private int cityId;

    private String cityName;

    private String cityIntroduce;

    public City(int cityId, String cityName, String cityIntroduce) {

        this.cityId = cityId;

        this.cityName = cityName;

        this.cityIntroduce = cityIntroduce;

    }

    public City(String cityName, String cityIntroduce) {

        this.cityName = cityName;

        this.cityIntroduce = cityIntroduce;

    }

    public City() {

    }

    public int getCityId() {

        return cityId;

    }

    public void setCityId(int cityId) {

        this.cityId = cityId;

    }

    public String getCityName() {

        return cityName;

    }

    public void setCityName(String cityName) {

        this.cityName = cityName;

    }

    public String getCityIntroduce() {

        return cityIntroduce;

    }

    public void setCityIntroduce(String cityIntroduce) {

        this.cityIntroduce = cityIntroduce;

    }

}

然后就是jpa的重要地方，CityRepository，继承了JpaRepository，

由于本文只是简单介绍了jpa的简单功能，所以JpaRepository中内置的方法已经足够使用。

代码如下：

package com.dalaoyang.repository;

import com.dalaoyang.entity.City;

import org.springframework.data.jpa.repository.JpaRepository;

/**

 * @author dalaoyang

 * @Description

 * @project springboot_learn

 * @package com.dalaoyang.Repository

 * @email 397600342@qq.com

 * @date 2018/4/7

 */

public interface CityRepository extends JpaRepository<City,Integer> {

}

最后是controller，里面和mybatis整合一样，方法上面写的就是对应的测试方法。

package com.dalaoyang.controller;

import com.dalaoyang.entity.City;

import com.dalaoyang.repository.CityRepository;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

/**

 * @author dalaoyang

 * @Description

 * @project springboot_learn

 * @package com.dalaoyang.controller

 * @email 397600342@qq.com

 * @date 2018/4/7

 */

@RestController

public class CityController {

    @Autowired

    private CityRepository cityRepository;

    //http://localhost:8888/saveCity?cityName=北京&cityIntroduce=中国首都

    @GetMapping(value = "saveCity")

    public String saveCity(String cityName,String cityIntroduce){

        City city = new City(cityName,cityIntroduce);

        cityRepository.save(city);

        return "success";

    }

    //http://localhost:8888/deleteCity?cityId=2

    @GetMapping(value = "deleteCity")

    public String deleteCity(int cityId){

        cityRepository.delete(cityId);

        return "success";

    }

    //http://localhost:8888/updateCity?cityId=3&cityName=沈阳&cityIntroduce=辽宁省省会

    @GetMapping(value = "updateCity")

    public String updateCity(int cityId,String cityName,String cityIntroduce){

        City city = new City(cityId,cityName,cityIntroduce);

        cityRepository.save(city);

        return "success";

    }

    //http://localhost:8888/getCityById?cityId=3

    @GetMapping(value = "getCityById")

    public City getCityById(int cityId){

        City city = cityRepository.findOne(cityId);

        return city;

    }

}

到这里启动项目就可以简单测试一下整合的效果了。

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