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Spring Boot2.x集成JPA Spring Boot2.x集成JPA快速开发的代码实例

拾荒者的笔记 人气:0

 什么是JPA

一种规范,并非ORM框架,也就是ORM上统一的规范

解决

用了之后可以做什么,为什么要用?如下代码解释

实体类

package com.example.springredis.entity;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import java.io.Serializable;

@Entity
@Data
public class User implements Serializable {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;
  private String name;
  private String account;
  private String pwd;

}

dao层

@Repository
public interface UserDao extends JpaRepository<User, Long> {

}

测试类

@Autowired
  private UserDao userDao;

  public void findAllTest() {
    System.out.println(userDao.findAll().toString());
  }

上面的操作已经完成了一个查询全部,相信不用在做多余的解释了

JPA优点:主要就是简单易用,集成方便,可以不用写SQL语句

准备工作

这里使用的是Maven,下载之后请在IDEA导入项目

项目结构图

先看pom.xml配置

国外依赖下载慢,更换阿里源

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
     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>2.3.0.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>
  <groupId>com.example</groupId>
  <artifactId>springboot-jpa</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>springboot-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-data-jpa</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
      <groupId>com.h2database</groupId>
      <artifactId>h2</artifactId>
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
    </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>

  <repositories>
    <!--阿里云主仓库,代理了maven central和jcenter仓库-->
    <repository>
      <id>aliyun</id>
      <name>aliyun</name>
      <url>https://maven.aliyun.com/repository/public</url>
      <releases>
        <enabled>true</enabled>
      </releases>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
    </repository>
    <!--阿里云代理Spring 官方仓库-->
    <repository>
      <id>spring-milestones</id>
      <name>Spring Milestones</name>
      <url>https://maven.aliyun.com/repository/spring</url>
      <releases>
        <enabled>true</enabled>
      </releases>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
    </repository>
  </repositories>

</project>

定义一个实体对象 SysUser.java

package com.example.demo.model;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity(name = "sys_user")
public class SysUser {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  private String email;

  private String username;

  private String password;

  public SysUser(String email, String username, String password) {
    this.email = email;
    this.username = username;
    this.password = password;
  }
}

 创建一个 UserRepository.java 接口

这里很简单,直接继承核心接口 JpaRepository

package com.example.demo.repository;

import com.example.demo.model.SysUser;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<SysUser, Long> {

}

配置文件application.yml

修改application.properties 为 application.yml

src/main/resources/application.yml

spring:
 datasource:
  driverClassName: org.h2.Driver
  password: root
  url: jdbc:h2:mem:demodb:file:data/demo
  username: root
 jpa:
  open-in-view: true
  database-platform: org.hibernate.dialect.H2Dialect
  # spring.jpa.show-sql=true 配置在日志中打印出执行的 SQL 语句信息。
  show-sql: true
  # 配置指明在程序启动的时候要删除并且创建实体类对应的表。
  # create 这个参数很危险,因为他会把对应的表删除掉然后重建。所以千万不要在生成环境中使用。只有在测试环境中,一开始初始化数据库结构的时候才能使用一次。
  # ddl-auto:create----每次运行该程序,没有表格会新建表格,表内有数据会清空
  # ddl-auto:create-drop----每次程序结束的时候会清空表
  # ddl-auto:update----每次运行程序,没有表格会新建表格,表内有数据不会清空,只会更新(推荐)
  # ddl-auto:validate----运行程序会校验数据与数据库的字段类型是否相同,不同会报错
  hibernate.ddl-auto: update

h2数据库

在resources 文件夹下新建 data.sql

data.sql

DROP TABLE IF EXISTS sys_user;

CREATE TABLE sys_user
(
  id    INT AUTO_INCREMENT PRIMARY KEY,
  email  VARCHAR(250) DEFAULT NULL,
  username VARCHAR(250) NOT NULL,
  password VARCHAR(250) NOT NULL
);

测试类进行测试 SpringbootJpaApplicationTests.java

package com.example.demo;

import com.example.demo.model.SysUser;
import com.example.demo.repository.UserRepository;
import lombok.extern.slf4j.Slf4j;
import org.junit.After;
import org.junit.Before;
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;

@Slf4j
@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringbootJpaApplicationTests {

  @Autowired
  private UserRepository userRepository;

  @Before
  public void add() {
    userRepository.save(new SysUser("123@qq.com", "root", "root"));
  }

  @Test
  public void contextLoads() {
    System.out.println(userRepository.findAll().toString());
  }

  //修改操作
  @After
  public void update() {
    // ifPresent 如果存在值,则使用值调用指定的使用者,否则不执行任何操作。
    userRepository.findById(1L).ifPresent(user -> {
      user.setUsername("马华云腾");
      userRepository.save(user);
      System.out.println(user.toString());
    });
  }

  //删除
  @After
  public void del() {
    userRepository.findById(2L).ifPresent(user -> userRepository.delete(user));
  }

}

测试输出

常见异常

如果出现下列等错误:

Error:(41, 13) java: 找不到符号
符号: 方法 setName(java.lang.String)
位置: 类型为com.example.springbootjpademo.entity.User的变量 user

请注意下面的设置是否正确:

RestClient API 测试

### 新增1

POST http://localhost:8080/user/add
Content-Type: application/json

{
 "email": "eyck@aws.com",
 "username": "root",
 "password": "root"
}

### 新增2

POST http://localhost:8080/user/add
Content-Type: application/json

{
"email": "ekko@aws.com",
"username": "ekko",
"password": "ekko"
}

### 修改

PUT http://localhost:8080/user/update
Content-Type: application/json

{
 "id": 1,
 "email": "eyck@aws.com",
 "username": "root",
 "password": "root"
}

### 获取所有
GET http://localhost:8080/user/all
Accept: */*
Cache-Control: no-cache

### 删除

PUT http://localhost:8080/user/del/2

### 获取所有
GET http://localhost:8080/user/all
Accept: */*
Cache-Control: no-cache

左上角 Run all ...

测试结果....

代码地址

https://github.com/Gleans/spring-boot/tree/master/springboot-jpa

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