JPA全称(Java Persistence API),JPA 的目标之一是制定一个可以由很多供应商实现的API，不了解的小伙伴...emm虽然没人看，，可以看一下我的JPA系列学习笔记，JPA学习笔记emm..日后再改。
整个pom文件

<?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.yjj</groupId>
    <artifactId>sb-first</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>sb-first</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.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>
        <!-- You can easily generate your own configuration metadata file
         from items annotated with @ConfigurationProperties by using the
         spring-boot-configuration-processor jar.
        -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <!-- mysql连接-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!-- jpa -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa
            </artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

配置文件application.yml加入

spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
    username: root
    password: 123456

  jpa:
    hibernate:
      ddl-auto: update  # 第一次简表create  后面用update
    show-sql: true

注意，如果通过jpa在数据库中建表，将jpa.hibernate,ddl-auto改为create，建完表之后，要改为update,要不然每次重启工程会删除表并新建。

创建实体类

通过@Entity 表明是一个映射的实体类， @Id表明id， @GeneratedValue 字段自动生成

package com.yjj.sbfirst.entity;

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

@Table(name="account")
@Entity
public class Account {
    @Id
    @GeneratedValue
    private int id;
    private String name;
    private double money;

    //省略getter setter
}

service层

package com.yjj.sbfirst.repository;
import com.yjj.sbfirst.entity.Account;
import org.springframework.data.jpa.repository.JpaRepository;

public interface AccountRepository extends JpaRepository<Account,Integer>{

}

Controller层

package com.yjj.sbfirst.controller;

import com.yjj.sbfirst.entity.Account;
import com.yjj.sbfirst.repository.AccountRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping(value = "/account")
public class AccountController {
    @Autowired
    AccountRepository accountRepository;

    @RequestMapping(value="/list")
    public List<Account> getAccounts(){
        return accountRepository.findAll();
    }

    @RequestMapping(value = "/{id}",method = RequestMethod.GET)
    public String getAccountById(@PathVariable("id") int id){
        return accountRepository.findById(0).get().toString();
    }

    @RequestMapping(value = "/update/{id}",method = RequestMethod.POST)
    public String updateAccount( @PathVariable("id") int id,@RequestParam(value="name",required = true) String name,
                                @RequestParam(value="money",required = true) double money){
        Account account=new Account();
        account.setMoney(money);
        account.setName(name);
        account.setId(id);
        Account account1=accountRepository.saveAndFlush(account);
        return account1.toString();
    }


}

以上代码均测试过，就是有的没通过。。emm。。findOne和findByID返回Optional是怎么搞啊。。
查询全部和更新是可以的。嗯，暂时到这里