（四）SpringBoot——JPA

1、JPA

JPA（Java Persistence API），經過JDK5註解或者xml描述對象-關係表的映射關係，並將運行期的實體對象持久化到數據庫中。

例如，開源的Hibernate就是遵循JPA規範的，咱們常常用到的Mybatis其實並無遵循JPA規範。固然，和編程語言同樣，持久層的框架沒有好壞之分，更重要的是，是否符合你的業務需求。

 

2、構建JPA項目流程

一、經過IDEA編譯器建立，以下圖所示：

二、pom依賴

根據上圖的配置，將自動生成pom.xml文件的配置以下：

<?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.solid4j</groupId>
	<artifactId>springboot-jpa</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>springboot-jpa</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.1.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>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>

三、編寫JPA數據源

咱們此次採用yml文件進行數據源的配置（SpringBoot是支持多種類型的配置文件的，application.yml的配置結構以下所示）

spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
    username: root
    password: root
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    database: mysql

四、定義model

/*
 * Copyright (c) 2018 solidwang. All Rights Reserved
 */
package com.solid4j.model;
import javax.persistence.*;

/**
 * @author: solidwang
 * @date：2018/4/23 上午11:20
 */
@Entity
@Table(name = "t_user")
public class User {

    @Id
    @GeneratedValue
    @Column(name = "id")
    private Integer id;

    @Column(name = "user_name")
    private String username;

    @Column(name = "passport")
    private String passport;

    @Column(name = "age")
    private Integer age;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassport() {
        return passport;
    }

    public void setPassport(String passport) {
        this.passport = passport;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", passport='" + passport + '\'' +
                ", age=" + age +
                '}';
    }
}

五、定義controller

/*
 * Copyright (c) 2018 solidwang. All Rights Reserved
 */
package com.solid4j.controller;

import com.solid4j.model.User;
import com.solid4j.service.UserJPA;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author: solidwang
 * @date：2018/4/23 上午11:37
 */
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserJPA userJPA;

    @RequestMapping(value = "/list", method = RequestMethod.GET)
    public List<User> list() {
        return userJPA.findAll();
    }

    @RequestMapping(value = "/save", method = RequestMethod.GET)
    public User save(User user) {
        return userJPA.save(user);
    }

    @RequestMapping(value = "/delete", method = RequestMethod.GET)
    public List<User> delete(User user) {
        userJPA.delete(user);
        return userJPA.findAll();
    }
}

六、進行數據測試

啓動服務進行測試