JPA的基本使用

前提：

　　创建一个springboot项目

　　创建一个名为springboottest的MySQL数据库

　　

1 jar包准备

　　jpa的jar包

　　mysql驱动的jar包

　　druid数据库连接池的jar包

　　lombok工具jar包

　　注意01： druid的jar包在都如时一定要指定版本，其它的spring boot项目会自动进行版本管理

<?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>cn.xiangxu</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
 
    <name>springboot</name>
    <description>Demo project for Spring Boot</description>
 
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.8.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-web</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
 
        <!--数据库相关-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.19</version>
        </dependency>
 
        <!--工具-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
 
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
 
</project>

pom.xml

2 数据库连接池配置和JPA配置

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource # 指定使用druid连接池
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: 182838
    url: jdbc:mysql://127.0.0.1/springboottest?characterEncoding=utf-8&useSSL=false
 
    #最大活跃数
    maxActive: 20
    #初始化数量
    initialSize: 1
    #最大连接等待超时时间
    maxWait: 60000
    #打开PSCache，并且指定每个连接PSCache的大小
    poolPreparedStatements: true
    maxPoolPreparedStatementPerConnectionSize: 20
    #通过connectionProperties属性来打开mergeSql功能；慢SQL记录
    #connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: select 1 from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    #配置监控统计拦截的filters，去掉后监控界面sql将无法统计,'wall'用于防火墙
    filters: stat, wall, log4j
 
  jpa:
    show-sql: true
    hibernate:
      ddl-auto: update
#      format-sql: true # TODO: 配置失败

连接池和JPA配置

package cn.xiangxu.springboot.baseConfig;
 
import com.alibaba.druid.support.http.StatViewServlet;
import com.alibaba.druid.support.http.WebStatFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
/**
 * 配置DRUID访问的Sevlet和filter
 */
@Configuration
public class DruidConfiguration {
 
    @Bean
    public ServletRegistrationBean statViewServlet(){
        //创建servlet注册实体
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(new StatViewServlet(),"/druid/*");
        //设置ip白名单
        servletRegistrationBean.addInitParameter("allow","127.0.0.1");
        //设置ip黑名单，如果allow与deny共同存在时,deny优先于allow
        servletRegistrationBean.addInitParameter("deny","192.168.0.19");
        //设置控制台管理用户
        servletRegistrationBean.addInitParameter("loginUsername","wys");
        servletRegistrationBean.addInitParameter("loginPassword","123456");
        //是否可以重置数据
        servletRegistrationBean.addInitParameter("resetEnable","false");
        return servletRegistrationBean;
    }
 
    @Bean
    public FilterRegistrationBean statFilter(){
        //创建过滤器
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(new WebStatFilter());
        //设置过滤器过滤路径
        filterRegistrationBean.addUrlPatterns("/*");
        //忽略过滤的形式
        filterRegistrationBean.addInitParameter("exclusions","*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        return filterRegistrationBean;
    }
}

druid的servlet和filter配置

jpa基础配置详解：点击前往

druid配置详解：点击前往

3 创建一个实体类

　　实体类相关注解说明：点击前往

　　技巧01：lombok的妙用

　　注意01：使用lombok的坑 -> 即使导入了相关的jar包，lombok的注解在IDEA中时不会生效的，但是项目进行打包后就会生效 -> 解决办法

package cn.xiangxu.springboot.entity.dataObject;
 
import lombok.Data;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
 
@Entity
@Data
public class Girl {
    @Id
    @GeneratedValue
    @Column(name = "girlId")
    private Integer id;
    private Integer age;
    private String name;
 
    public Girl() {
    }
 
    public Girl(Integer age, String name) {
        this.age = age;
        this.name = name;
    }
}

实体类

4 创建一个与实体类对应的持久层接口

　　注意01：该接口需要实现一个特定的父接口JpaRepository，继承了这个接口后就该接口就会自动被容器管理，无需再添加注解

chijge cn.xiangxu.springboot.repository;
 
import cn.xiangxu.springboot.entity.dataObject.Girl;
import org.springframework.data.jpa.repository.JpaRepository;
 
public interface GirlRepository extends JpaRepository<Girl, Integer> {
 
}

持久层接口

5 创建一个服务层接口

　　调用持久层对象的相应方法实现简单的增删改查操作

package cn.xiangxu.springboot.service;
 
import cn.xiangxu.springboot.entity.dataObject.Girl;
 
import java.util.List;
 
public interface GirlService {
    Girl saveGirl(Girl girl);
    Girl findGirlOne(Integer id);
    List<Girl> finGirldAll();
}

服务层接口

package cn.xiangxu.springboot.service.serviceImpl;
 
import cn.xiangxu.springboot.entity.dataObject.Girl;
import cn.xiangxu.springboot.repository.GirlRepository;
import cn.xiangxu.springboot.service.GirlService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
import java.util.List;
 
@Service("girlService")
public class GirlServiceImpl implements GirlService {
    @Autowired
    private GirlRepository girlRepository;
 
    @Override
    public Girl saveGirl(Girl girl) {
        return girlRepository.save(girl);
    }
 
    @Override
    public Girl findGirlOne(Integer id) {
        return girlRepository.findOne(id);
    }
 
    @Override
    public List<Girl> finGirldAll() {
        return girlRepository.findAll();
    }
}

服务层接口实现类

6 创建服务层测试类

package cn.xiangxu.springboot.service.serviceImpl;
 
import cn.xiangxu.springboot.entity.dataObject.Girl;
import cn.xiangxu.springboot.service.GirlService;
import lombok.extern.slf4j.Slf4j;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
 
import java.util.List;
 
import static org.junit.Assert.*;
 
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j // 日志相关
public class GirlServiceImplTest {
 
    @Autowired
    private GirlService girlService;
 
    @Test
    public void saveGirl() throws Exception {
        Girl girl = new Girl(25, "三少");
        Girl result = girlService.saveGirl(girl);
        log.info("【插入数据】");
        Assert.assertNotEquals(null, result);
    }
 
    @Test
    public void findGirlOne() throws Exception {
        Girl result = girlService.findGirlOne(1);
        log.info("【查询单个】");
        Assert.assertEquals(new Integer(1), result.getId());
    }
 
    @Test
    public void finGirldAll() throws Exception {
        List<Girl> girls = girlService.finGirldAll();
        log.info("查询列表");
        Assert.assertNotEquals(new Integer(0), new Integer(girls.size()));
    }
 
}

服务层测试类

7 具体使用02

　　说明：不使用数据库连接池，这里只是给出一些特殊的地方

　　坑01：springboot版本升级后，实体类中的id字段必须根据数据库类型设定对应的默认主键值产生类型

package cn.xiangxu.jpa_demo01.domain.domain_do;
 
import lombok.Data;
 
import javax.persistence.*;
 
/**
 * @author 王杨帅
 * @create 2018-08-12 15:01
 * @desc
 **/
@Entity
@Table(name = "student")
@Data
public class Student {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private String id;
    private String name;
    private Integer age;
    private String address;
}

Student.java

spring:
  datasource:
    url: jdbc:mysql://127.0.0.1/testdemo?characterEncoding=utf-8&useSSL=false
    username: root
    password: 182838
 
  jpa:
    properties:
      hibernate:
        format_sql: true
        show_sql: true

配置类

package cn.xiangxu.jpa_demo01.repository;
 
import cn.xiangxu.jpa_demo01.domain.domain_do.Student;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
 
import java.util.List;
 
import static org.junit.Assert.*;
 
@RunWith(SpringRunner.class)
@SpringBootTest
public class StudentRepositoryTest {
 
    @Autowired
    private StudentRepository studentRepository;
 
    @Test
    public void findAll() {
        List<Student> all = studentRepository.findAll();
        Assert.assertTrue(all.size() > 0);
    }
 
}

测试类