==> 学习汇总（持续更新）
==> 从零搭建后端基础设施系列（一）-- 背景介绍

---

注：我是在mac下搭建的demo，在windows下同理，这个不存在什么太大差异。后面会有源码，直接导入idea即可，只是环境的配置稍有不同。

一、准备工作
下载最新版idea.。
下载mysql。
下载postman，这是一款用于前后端接口请求测试的神器。
以上自行百度安装。

二、创建项目

1.new project->选择 spring initalizr

3.这里只需要选web就可以了

4.最后只需要填写项目路径以及名字就行了

5.目录结构

6.打开pom文件，添加几个依赖

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-jdbc</artifactId>
			<version>RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.mybatis</groupId>
			<artifactId>mybatis</artifactId>
			<version>RELEASE</version>
		</dependency>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.25</version>
		</dependency>

三、配置mybatis
1.配置mybatis xml文件，该文件放在resource下
文件名：spring-mybatis.xml
代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    <!--这里是全局配置，具体的可以去查mybatis配置-->
    <settings>
        <setting name="cacheEnabled" value="false" />
        <setting name="useGeneratedKeys" value="true" />
        <setting name="defaultExecutorType" value="REUSE" />
    </settings>
    <!--别名，就是将后面那一堆，用User代替-->
    <typeAliases>
        <typeAlias alias="User" type="com.example.springboot.demo.bean.User"/>
    </typeAliases>
    <!--环境配置-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="jdbc"/>
            <!--连接数据库-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_test"/>
                <property name="username" value="root"/>
                <property name="password" value="acme1234"/>
            </dataSource>
        </environment>
    </environments>
    <!--这个就是指定映射的xml，mapper xml中的SQL查询 都要对应java接口类里面的方法-->
    <mappers>
        <mapper resource="mappers/mapper-mybatis.xml"/>
    </mappers>
</configuration>

2.创建userMapper.xml文件

代码如下：

<?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.example.springboot.demo.UserMapper">

    <!--id对应接口中的方法，名字要一样，parameterType是方法的参数类型，
    resultType是查询返回的类型，需要注意的是，这里的SQL语句后面不能加分号，变量不能加引号-->
    <select id="getById" parameterType="int" resultType="User">
        select * from user where id = #{id}
    </select>

    <insert id="insert" parameterType="string">
        insert into user(name) values(#{name})
    </insert>

    <select id="getUsers"  resultType="User">
        select * from user order by #{id}
    </select>

    <update id="updateUser" parameterType="User">
        update user set name=#{name} where id = #{id}
    </update>
    <delete id="deleteAllUsers">
        delete from user
    </delete>
    <delete id="deleteUser" parameterType="int">
        delete from user where id = #{id}
    </delete>

</mapper>

3.创建User类和UserMapper接口类

User类代码：

package com.example.springboot.demo.bean;


public class User {
    private String name;
    private int id;

    public User(){

    }
    public User(int id,String name){
        this.id = id;
        this.name = name;
    }
    public String getName() {
        return name;
    }

    public int getId() {
        return id;
    }

    public void setName(String name) {
        this.name = name;
    }

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

}

UserMapper类代码:

package com.example.springboot.demo.Mapper;

import com.example.springboot.demo.bean.User;

import java.util.List;

public interface UserMapper {
    public User getById(int id);
    public boolean insert(String name);
    public List<User> getUsers();
    public boolean updateUser(User user);
    public boolean deleteUser(int id);
    public boolean deleteAllUsers();
}

4.为mybatis创建单例模式类

代码如下：

package com.example.springboot.demo.singleton;

import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class SingletonMybatis {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "spring-mybatis.xml";
        Reader reader = null;
        try {
            reader = Resources.getResourceAsReader(resource);
        } catch (IOException e) {
            System.out.println(e.getMessage());

        }
        //这里相当于生成一个数据库管理者，它可以返回一个连接给使用者。
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    }

    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }
}

四、实现Controller并设计 restful api
restful是什么？
如何设计restful api

Controller类代码如下：

package com.example.springboot.demo.controller;

import com.example.springboot.demo.Mapper.UserMapper;
import com.example.springboot.demo.bean.User;
import com.example.springboot.demo.singleton.SingletonMybatis;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/index") //在类上使用RequestMapping，里面设置的value就是方法的父路径
public class Controller {

    private static SqlSessionFactory sqlSessionFactory;
    static {
        sqlSessionFactory =  SingletonMybatis.getSqlSessionFactory();
    }
    @RequestMapping  //如果方法上的RequestMapping没有value，则此方法默认被父路径调用
    public String index(){
        return "hello spring boot";
    }
    //这里体现了restful风格的请求，按照请求的类型，来进行增删查改。
    //设计restful api（其实也就是URL），不要有冗余，例如不要写成getUsers，URL中
    //最好不要有动词。
    @RequestMapping(method = RequestMethod.GET,value = "/users")
    public List<User> getUsers(){
        List<User> listUsers;
        //获取一个连接
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            //得到映射器
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            //调用接口中的方法去执行xml文件中的SQL语句
            listUsers = userMapper.getUsers();
            //要提交后才会生效
            sqlSession.commit();
        }finally {
            //最后记得关闭连接
            sqlSession.close();
        }

        return listUsers;
    }
    //这里用的是路径变量，就是{}括起来的，会当做变量读进来
    @RequestMapping(method = RequestMethod.GET,value = "/users/{userId}")
    public User getUser(@PathVariable int userId){
        User user;
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            user = userMapper.getById(userId);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
        return user;
    }
    //RequestBody这个注解可以接收json数据
    @RequestMapping(method = RequestMethod.POST,value = "/user")
    public boolean setUser(@RequestBody String name){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            userMapper.insert(name);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
        return true;
    }
    @RequestMapping(method = RequestMethod.PUT,value = "/user/{userid}/{name}")
    public boolean updateUser(@PathVariable int userid,@PathVariable String name){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            User user = new User(userid,name);
            userMapper.updateUser(user);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
        return true;
    }

    @RequestMapping(method = RequestMethod.DELETE,value = "/users")
    public boolean deleteUsers(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            userMapper.deleteAllUsers();
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
        return true;
    }

    @RequestMapping(method = RequestMethod.DELETE,value = "/users/{userId}")
    public boolean deleteUser(@PathVariable int userId){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            userMapper.deleteUser(userId);
            sqlSession.commit();
        }finally {
            sqlSession.close();
        }
        return true;
    }


}

五.在mysql中创建mybatis_test数据库以及User表

这里就省略了，要注意的是User表的字段和类型都要和User类中的字段一致。

六.用postman测试接口是否正常

六.源码下载

github
csdn