springboot整合mybatis（映射文件方式和注解方式）

　　springboot作为一个微服务框架，给我们开发人员提供极大的便利，秉着约定大于配置的原则，通过starter包的形式为我们做了许多默认的配置，在进行数据持久化到关系型数据库时，我们一般都会首选spring data jpa，springboot为我们提供了starter包，只需配置很少的参数，就能满足我们的需求，非常方便。但是当我们遇到一些比较复杂的查询、多表关联查询及动态sql时，mybatis则在这方面更出色，并且在使用mybatis时我们可以通过sql优化来提高查询效率，springboot并没有给我们提供整合mybatis的starter包，因此我们需要自己整合。记录一下我的整合过程，以供后续参考。

　　本人使用的是sts，新建springboot项目加入web、mysql、mybatis模块，springboot版本2.0.1。

　　1、pom.xml

<?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.example</groupId>
	<artifactId>springboot-mybatis</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

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

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.0.BUILD-SNAPSHOT</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.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>1.3.2</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>

		 <!-- 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.5</version>
        </dependency>
        <!-- alibaba的druid数据库连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.9</version>
        </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>

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>

	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</pluginRepository>
	</pluginRepositories>

</project>

　　2、实体类UserDomain.java

package com.example.demo.model;

public class UserDomain {
    private Integer userId;

    private String userName;

    private String password;

    private String phone;

    //get和set方法
}

　　3、持久化接口

package com.example.demo.dao;

import java.util.List;

import com.example.demo.model.UserDomain;

public interface UserDao {

    int insert(UserDomain record);

    List<UserDomain> selectUsers();
}

　　4、建表语句，注意数据库的ip和名称

CREATE TABLE t_user(
  user_id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
  user_name VARCHAR(255) NOT NULL ,
  password VARCHAR(255) NOT NULL ,
  phone VARCHAR(255) NOT NULL
) ENGINE=INNODB AUTO_INCREMENT=1000 DEFAULT CHARSET=utf8;

　　5、service层

package com.example.demo.service;

import com.example.demo.model.UserDomain;
import com.github.pagehelper.PageInfo;

public interface UserService {

    int addUser(UserDomain user);

    PageInfo<UserDomain> findAllUser(int pageNum, int pageSize);
}

package com.example.demo.service.impl;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.example.demo.dao.UserDao;
import com.example.demo.model.UserDomain;
import com.example.demo.service.UserService;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;

@Service(value = "userService")
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;

    @Override
    public int addUser(UserDomain user) {

        return userDao.insert(user);
    }

    //分页查询
    @Override
    public PageInfo<UserDomain> findAllUser(int pageNum, int pageSize) {
        PageHelper.startPage(pageNum, pageSize);
        List<UserDomain> userDomains = userDao.selectUsers();
        PageInfo result = new PageInfo(userDomains);
        return result;
    }
}

　　6、控制层

package com.example.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import com.example.demo.model.UserDomain;
import com.example.demo.service.UserService;

@Controller
@RequestMapping(value = "/user")
public class UserController {

    @Autowired
    private UserService userService;

    @ResponseBody
    @PostMapping("/add")
    public int addUser(UserDomain user){
        return userService.addUser(user);
    }

    @ResponseBody
    @GetMapping("/all")
    public Object findAllUser(
            @RequestParam(name = "pageNum", required = false, defaultValue = "1")
                    int pageNum,
            @RequestParam(name = "pageSize", required = false, defaultValue = "10")
                    int pageSize){
        return userService.findAllUser(pageNum,pageSize);
    }
}

　　7、application.yml

server:
  port: 8080

spring:
    datasource:
        name: mysql_test
        type: com.alibaba.druid.pool.DruidDataSource
        #druid相关配置
        druid:
          #监控统计拦截的filters
          filters: stat
          driver-class-name: com.mysql.jdbc.Driver
          #基本属性
          url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
          username: root
          password: root
          #配置初始化大小/最小/最大
          initial-size: 1
          min-idle: 1
          max-active: 20
          #获取连接等待超时时间
          max-wait: 60000
          #间隔多久进行一次检测，检测需要关闭的空闲连接
          time-between-eviction-runs-millis: 60000
          #一个连接在池中最小生存的时间
          min-evictable-idle-time-millis: 300000
          validation-query: SELECT 'x'
          test-while-idle: true
          test-on-borrow: false
          test-on-return: false
          #打开PSCache，并指定每个连接上PSCache的大小。oracle设为true，mysql设为false。分库分表较多推荐设置为false
          pool-prepared-statements: false
          max-pool-prepared-statement-per-connection-size: 20

mybatis:
  mapper-locations: classpath:mapper/*.xml
  type-aliases-package: com.example.demo.model

#pagehelper
pagehelper:
    helperDialect: mysql
    reasonable: true
    supportMethodsArguments: true
    params: count=countSql
    returnPageInfo: check

　　8、UserMapper.xml

<?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.demo.dao.UserDao" >
  <sql id="BASE_TABLE">
    t_user
  </sql>

  <sql id="BASE_COLUMN">
    userId,userName,password,phone
  </sql>

  <insert id="insert" parameterType="com.example.demo.model.UserDomain">
    INSERT INTO
      <include refid="BASE_TABLE"/>
    <trim prefix="(" suffix=")" suffixOverrides=",">
      userName,password,
      <if test="phone != null">
        phone,
      </if>
    </trim>
    <trim prefix="VALUES(" suffix=")" suffixOverrides=",">
      #{userName, jdbcType=VARCHAR},#{password, jdbcType=VARCHAR},
      <if test="phone != null">
        #{phone, jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>

  <select id="selectUsers" resultType="com.example.demo.model.UserDomain">
      SELECT
        <include refid="BASE_COLUMN"/>
      FROM
        <include refid="BASE_TABLE"/>
  </select>

</mapper>

　　9、项目目录结构如下

　　在项目启动类SpringbootMybatisApplication上加上@MapperScan("com.example.demo.dao")注解，以便spring容器可以扫描到持久化接口，创建对应的代理类。springboot默认为mybatis、jpa、jdbc等开启了事务，如果需要开启事务，则在service层对应的方法上加上@Transactional即可。启动项目，访问localhost:8080/user/add,添加用户；访问localhost:8080/user/all，可以看到分页查询效果。

　　补充：相比与映射文件方式，注解方式会更加方便，但是功能有限，使用注解方式只需做如下修改即可

　　1、持久化接口修改为如下

package com.example.demo.dao;

import java.util.List;

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

import com.example.demo.model.UserDomain;

@Mapper
public interface UserDao {

	@Insert("INSERT INTO t_user(name, password, phone) VALUES(#{name}, #{password}, #{phone})")
	 int insert(@Param("name") String name, @Param("password") String password, @Param("phone") String phone);

	@Select("SELECT * FROM t_user ")
    List<UserDomain> selectUsers();
}

　　2、删除掉UserMappper.xml文件即可。