IntelliJ IDEA 2017版 spring-boot使用Spring Data JPA搭建基础版的三层架构

1、配置环境pom

<?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.spring</groupId>
    <artifactId>boot_jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>boot_jpa</name>
    <url>http://maven.apache.org</url>
    <description>Demo project for Spring Boot</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-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!--自定义配置文件-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.15</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>


        <!-- 添加fastjson 依赖包. -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.15</version>
        </dependency>

        <!-- spring boot devtools 依赖包. -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
            <scope>true</scope>
        </dependency>

        <!-- 添加MySQL数据库驱动依赖包. -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <!-- 添加Spring-data-jpa依赖. -->
        <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>
                <configuration>
                    <!--fork :  如果没有该项配置，肯呢个devtools不会起作用，即应用不会restart -->
                    <fork>true</fork>
                </configuration>
            </plugin>
        </plugins>
    </build>


</project>

2、建立数据库连接的application.properties

#######################################################
##datasource -- 指定mysql数据库连接信息.
#######################################################
spring.datasource.url = jdbc:mysql://localhost:3306/test
spring.datasource.username = root
spring.datasource.password = 123456
spring.datasource.driverClassName = com.mysql.jdbc.Driver
spring.datasource.max-active=20
spring.datasource.max-idle=8
spring.datasource.min-idle=8
spring.datasource.initial-size=10


########################################################
### Java Persistence Api --  Spring jpa的配置信息.
########################################################
# Specify the DBMS
spring.jpa.database = MYSQL
# Show or not log for each sql query
spring.jpa.show-sql = true
# Hibernate ddl auto (create, create-drop, update)
spring.jpa.hibernate.ddl-auto = update
# Naming strategy
#[org.hibernate.cfg.ImprovedNamingStrategy  #org.hibernate.cfg.DefaultNamingStrategy]
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy
# stripped before adding them to the entity manager)
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

结构如图：
       

3、建立pojo实体类

package com.spring.boot.jap.perform.pojo;

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

/**
 * Created by liuya on 2018-01-26.
 */
@Entity
public class Cat {

    /**
     * 使用@Id指定主键.
     * <p>
     * 使用代码@GeneratedValue(strategy=GenerationType.AUTO)
     * 指定主键的生成策略，mysql默认的是自增长。
     */
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;//主键.

    private String catName;//姓名. cat_name

    private int catAge;//年龄. cat_age;

    public int getId() {
        return id;
    }

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

    public String getCatName() {
        return catName;
    }

    public void setCatName(String catName) {
        this.catName = catName;
    }

    public int getCatAge() {
        return catAge;
    }

    public void setCatAge(int catAge) {
        this.catAge = catAge;
    }

}

4、通过实体类自动生成数据库表（前提建立数据库，名称为test）

package com.spring.boot.jap.perform;

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;

import java.util.ArrayList;
import java.util.List;

@SpringBootApplication
//@ComponentScan(basePackages = {"com.spring.boot.service.*"})
public class BootJpaApplication {
    public static void main(String[] args) {
        SpringApplication.run(BootJpaApplication.class,args);
    }

    /**
     * 在这里我们使用 @Bean注入 fastJsonHttpMessageConvert
     *
     * @return
     */
    @Bean
    public HttpMessageConverters fastJsonHttpMessageConverters() {
        // 1、需要先定义一个 convert 转换消息的对象;
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();

        //2、添加fastJson 的配置信息，比如：是否要格式化返回的json数据;
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);

        //处理中文乱码
        List<MediaType> fastMediaTypes = new ArrayList<>();
        fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
        fastConverter.setSupportedMediaTypes(fastMediaTypes);

        //3、在convert中添加配置信息.
        fastConverter.setFastJsonConfig(fastJsonConfig);


        HttpMessageConverter<?> converter = fastConverter;
        return new HttpMessageConverters(converter);
    }
}

建立这个BootJpaApplication类中书写内容，然后run这个类，就会在数据库中产生cat的表

5、建立dao层

package com.spring.boot.jap.perform.dao;

import com.spring.boot.jap.perform.pojo.Cat;
import org.springframework.data.repository.CrudRepository;

/**
 * Created by liuya on 2018-01-27.
 */
public interface CatDao  extends CrudRepository<Cat, Integer> {
}

6、建立service层

package com.spring.boot.jap.perform.service;

import com.spring.boot.jap.perform.dao.CatDao;
import com.spring.boot.jap.perform.pojo.Cat;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import javax.transaction.Transactional;

/**
 * Created by liuya on 2018-01-27.
 */


@Service
public class CatService {

    @Resource
    private CatDao catRepository;

    /**
     * save,update ,delete 方法需要绑定事务.
     *
     * 使用@Transactional进行事务的绑定.
     *
     * @param cat
     */

    //保存数据.
    @Transactional
    public void save(Cat cat){
        catRepository.save(cat);
    }

    //删除数据》
    @Transactional
    public void delete(int id){
        catRepository.delete(id);
    }

    //查询数据.
    public Iterable<Cat> getAll(){
        return catRepository.findAll();
    }


}

7、建立controller层

package com.spring.boot.jap.perform.controller;

import com.spring.boot.jap.perform.pojo.Cat;
import com.spring.boot.jap.perform.service.CatService;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

/**
 * Created by liuya on 2018-01-27.
 */


@RestController
@RequestMapping("/cat")
public class CatController {

    @Resource
    private CatService catService;

    @RequestMapping("/save")
    public String save(){
        Cat cat = new Cat();
        cat.setCatName("jack");
        cat.setCatAge(3);
        catService.save(cat);
        return "save ok.";
    }

    //每次需要更改delete删除的id值,否则会报错
    @RequestMapping("/delete")
    public String delete(){
        catService.delete(2);
        return "delete ok";
    }

    @RequestMapping("/getAll")
    public Iterable<Cat> getAll(){
        return catService.getAll();
    }


}

8、测试代码是否成功，启动

9、浏览器访问，url：http://127.0.0.1:8080/cat/save    首先新建数据

                                  http://127.0.0.1:8080/cat/delete   删除id为1的数据

                                 http://127.0.0.1:8080/cat/getAll    显示全部数据，如果按照上两步，就只有2和之后的数据存在