Idea+springboot入坑之路

环境准备

IDEA 社区版: 2019.3
jdk: 1.8.0_241
tomcat: 7.0.99
maven: 3.6.3
spring-boot:2.2.5.RELEASE

插件

spring Assistant:解决社区版没有spring initializr
Smart Tomcat:解决社区版没有tomca
free mybatis plugin: 方便在mapper接口方法和mapper XML文件之间来回切换的插件

入坑之路

第一个接口，新建HomeController，@RequestMapping注解设定接口的路由，如下所示：

@RestController
public class HomeController {

    @RequestMapping("hello")
    public String hello()
    {
        return  "Hello World!";
    }
}

运行项目，在Postman中请求结果:

加上Mybatis

我在该项目中利用了mybatis，MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。用其他的框架也类似吧，大同小异，因为接触java时间比较短，之前一直从事.net方面的项目开发工作。

这是我建立的目录结构，分别建立了controller、entity、mapper、service包，按字面意思也很好理解了，控制器，实体，映射接口，服务。resources中加上mapping文件夹，用来存放xml映射。如下图所示。

配置

可以看出，我把application.properties配置文件删除了，用application.yml替换了，接下来看一下具体配置内容。

application.yml

spring:
  profiles:
    active: dev

application-dev.yml

server:
  port: 8080
spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://localhost:3306/testdb?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
    driver-class-name: com.mysql.cj.jdbc.Driver
  
mybatis:
  mapper-locations: classpath:mapping/*Mapper.xml
  type-aliases-package: com.supos.first.entity

datasource

比较简单，稍微记录下就可以。可能是因为我的环境比较新，提示com.mysql.jdbc.Driver 过时了，需要改成com.mysql.cj.jdbc.Driver。

mybatis

mapper-locations:映射的xml路径，xml的名称必须与mapper的接口名称一致。
type-aliases-package：实体类的包名

这样配置基本就OK了

码代码

首先修改入口函数，@MapperScan将mapper注入到Spring，扫描包。

@SpringBootApplication
@MapperScan("com.supos.first.mapper")
public class SuposApplication {

   public static void main(String[] args) {
      SpringApplication.run(SuposApplication.class, args);
   }
}

创建一个User实体类，很简单，只有三个字段。

package com.supos.first.entity;

/**
 * @Classname ResultInfo
 * @Description TODO
 * @Date 2020/3/26 13:47
 * @Created by zhanwei
 */
public class User {
    private Integer id;
    private String name;
    private Integer age;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
}

创建UserMapper接口，里面有三个接口

package com.supos.first.mapper;

import com.supos.first.entity.User;
import org.springframework.stereotype.Repository;
import java.util.List;

/**
 * @Classname ResultInfo
 * @Description TODO
 * @Date 2020/3/26 13:47
 * @Created by zhanwei
 */
@Repository
public interface UserMapper {

    List<User> GetAllUser();

    User GetUser(int id);

    int InsertUser(User user);
}

在resources/mapping文件夹下，新建一个UserMapper.xml文件，id必须与接口定义一样

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.supos.first.mapper.UserMapper">
    <resultMap id="userResultMap" type="com.supos.first.entity.User">
        <result column="ID" jdbcType="INTEGER" property="id" />
        <result column="Name" jdbcType="VARCHAR" property="name" />
        <result column="Age" jdbcType="INTEGER" property="age" />
    </resultMap>
    <select id="GetUser" parameterType="int" resultType="com.supos.first.entity.User">
        select * from user where ID = #{id}
    </select>
    <select id="GetAllUser" resultType="com.supos.first.entity.User">
        select * from user
    </select>
    <insert id="InsertUser" useGeneratedKeys="true" keyProperty="id" parameterType="com.supos.first.entity.User">
        insert into user(Name,Age)  values(#{name},#{age})
    </insert>
    
</mapper>

创建UserService服务类

package com.supos.first.service;

import com.supos.first.entity.User;
import com.supos.first.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;

/**
 * @Classname ResultInfo
 * @Description TODO
 * @Date 2020/3/26 13:47
 * @Created by zhanwei
 */
@Service
public class UserService {

    @Autowired
    UserMapper userMapper;

    public List<User> GetAllUser(){
        return userMapper.GetAllUser();
    }
     public User Sel(int id)
     {
         return userMapper.GetUser(id);
     }
    public int Insert(User user)
    {
        return userMapper.InsertUser(user);
    }
}

创建UserController控制器

package com.supos.first.controller;

import com.supos.first.entity.ResultInfo;
import com.supos.first.entity.User;
import com.supos.first.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;

/**
 * @Classname TestController
 * @Description TODO
 * @Date 2020/3/18 15:56
 * @Created by zhanwei
 */
@RestController
@RequestMapping("/testBoot")
public class UserController {
    @Autowired
    private UserService userService;

    @RequestMapping("getUser")
    public ResultInfo GetUser()
    {
        ResultInfo result=new ResultInfo();
        List<User> list=userService.GetAllUser();
        result.setData(list);
        result.setCode(200);
        result.setResult(true);
        return result;
    }

    @RequestMapping("getUser/{id}")
    public ResultInfo GetUser(@PathVariable int id)
    {
        ResultInfo result=new ResultInfo();
        User user=userService.Sel(id);
        result.setData(user);
        result.setCode(200);
        result.setResult(true);
        return result;
    }

    @RequestMapping(value = "Insert",method = RequestMethod.POST)
    public String InsertUser(@RequestBody User user)
    {
        int row=userService.Insert(user);
        ResultInfo result=new ResultInfo();
        if(row>0) {
            result.setResult(true);
            result.setCode(200);
        }
        else {
            result.setResult(false);
            result.setCode(0);
        }
        return result;
    }
}

为了返回结果的统一性，我定义了一个ResultInfo的类，所有返回结果都可以套用。

package com.supos.first.entity;

/**
 * @Classname ResultInfo
 * @Description TODO
 * @Date 2020/3/26 13:47
 * @Created by zhanwei
 */
public class ResultInfo {
    private boolean result;
    private Integer code;
    private String message;
    private Object data;

    public boolean getResult() {
        return result;
    }
    public void setResult(boolean result) {
        this.result = result;
    }
    public Object getData() {
        return data;
    }
    public void setData(Object data) {
        this.data = data;
    }
    public Integer getCode() {
        return code;
    }
    public void setCode(Integer code) {
        this.code = code;
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

这样就可以运行了。