• 通用Mapper可以简化对单表的CRUD操作
• PageHelper分页插件可以帮我们自动拼接分页SQL

1.引入依赖

         <!--  mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.3</version>
        </dependency>
        <!-- 通用mapper -->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>1.2.4</version>
        </dependency>
        <!-- pagehelper 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.10</version>
        </dependency>
     <!--    引入mysql    -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.34</version>
        </dependency>

2.配置文件

2.1 pom.xml

注意版本，过高可能会报错，不要改动版本

<plugin>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-maven-plugin</artifactId>
    <version>1.3.2</version>
    <dependencies>
        <!--        mybatis自动生成代码-->
        <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.2</version>
        </dependency>
        <!-- 通用mapper -->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>1.2.4</version>
        </dependency>
    </dependencies>
    <configuration>
        <!--允许移动生成的文件 -->
        <verbose>true</verbose>
        <!-- 是否覆盖 -->
        <overwrite>true</overwrite>
        <!-- 自动生成的配置 -->
        <configurationFile>src/main/resources/mybatis-generator.xml</configurationFile>
    </configuration>
</plugin>

2.2 application.yml

# 配置mybatis
mybatis:
  # type-aliases扫描路径
  type-aliases-package: com.springboot.bean
  # mapper xml实现扫描路径
  mapper-locations: classpath:mapper/*.xml
  property:
    order: BEFORE

#mappers 多个接口时逗号隔开
mapper:
  mappers: com.suruomo.springboot10mybatis.config.MyMapper
  not-empty: false
  identity: mysql

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

#数据源
spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: suruomo
    url: jdbc:mysql://127.0.0.1:3306/demo

2.3 mybatis-generator.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
<generatorConfiguration>
    <!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包，路径不要出现中文-->
    <classPathEntry
            location="D:\Java\MAVEN\maven_repository\mysql\mysql-connector-java\5.1.34\mysql-connector-java-5.1.34.jar"/>

    <context id="DB2Tables" targetRuntime="MyBatis3">
        <plugin type="tk.mybatis.mapper.generator.MapperPlugin">
            <!-- 该配置会使生产的Mapper自动继承MyMapper -->
            <property name="mappers" value="com.suruomo.springboot10mybatis.config.MyMapper"/>
            <!-- caseSensitive默认false，当数据库表名区分大小写时，可以将该属性设置为true -->
            <!--            <property name="caseSensitive" value="false"/>-->
        </plugin>
        <commentGenerator>
            <property name="javaFileEncoding" value="UTF-8"/>
            <property name="suppressDate" value="true"/>
            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="trur"/>
        </commentGenerator>
        <!--数据库链接URL，用户名、密码 -->
        <jdbcConnection
                driverClass="com.mysql.jdbc.Driver"
                connectionURL="jdbc:mysql://localhost:3306/demo?useUnicode=true" userId="root"
                password="suruomo">
        </jdbcConnection>

        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>

        <!-- 生成模型的包名和位置-->
        <javaModelGenerator targetPackage="com.suruomo.springboot10mybatis.model" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>

        <!-- 生成映射文件的包名和位置-->
        <sqlMapGenerator targetPackage="mapper" targetProject="src/main/resources">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>

        <!-- 生成DAO的包名和位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.suruomo.springboot10mybatis.mapper"
                             targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>

        <!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
        <table tableName="user" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false"
               enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="true"></table>
    </context>
</generatorConfiguration>

3.自动执行生成代码

生成UserMapper+User+UserMapper.xml

插件执行

4.代码

4.1 创建Mapper接口

import tk.mybatis.mapper.common.Mapper;
import tk.mybatis.mapper.common.MySqlMapper;

/**
 * @author suruomo
 * @date 2020/7/29 10:18
 * @description: 该接口不能被扫描到，应该和自己定义的Mapper分开。自己定义的Mapper都需要继承这个接口。
 */
public interface MyMapper<T> extends Mapper<T>, MySqlMapper<T> {
}

4.2 让生成的UserMapper接口继承MyMapper接口

@Mapper
public interface UserMapper extends MyMapper<User> {
}

4.3 创建公共Service

IService接口：

import org.springframework.stereotype.Service;

import java.util.List;

/**
 * @author suruomo
 * @date 2020/7/29 13:26
 * @description:
 */
@Service
public interface IService<T> {

    List<T> selectAll();

    T selectByKey(Object key);

    int save(T entity);

    int delete(Object key);

    int updateAll(T entity);

    int updateNotNull(T entity);

    List<T> selectByExample(Object example);

实现类BaseService：

import org.springframework.beans.factory.annotation.Autowired;
import tk.mybatis.mapper.common.Mapper;

import java.util.List;

/**
 * @author suruomo
 * @date 2020/7/29 13:26
 * @description:
 */
public  class BaseService<T> implements IService<T> {

    @Autowired
    protected Mapper<T> mapper;

    public Mapper<T> getMapper() {
        return mapper;
    }

    @Override
    public List<T> selectAll() {
        //说明：查询所有数据
        return mapper.selectAll();
    }

    @Override
    public T selectByKey(Object key) {
        //说明：根据主键字段进行查询，方法参数必须包含完整的主键属性，查询条件使用等号
        return mapper.selectByPrimaryKey(key);
    }

    @Override
    public int save(T entity) {
        //说明：保存一个实体，null的属性也会保存，不会使用数据库默认值
        return mapper.insert(entity);
    }

    @Override
    public int delete(Object key) {
        //说明：根据主键字段进行删除，方法参数必须包含完整的主键属性
        return mapper.deleteByPrimaryKey(key);
    }

    @Override
    public int updateAll(T entity) {
        //说明：根据主键更新实体全部字段，null值会被更新
        return mapper.updateByPrimaryKey(entity);
    }

    @Override
    public int updateNotNull(T entity) {
        //根据主键更新属性不为null的值
        return mapper.updateByPrimaryKeySelective(entity);
    }

    @Override
    public List<T> selectByExample(Object example) {
        //说明：根据Example条件进行查询
        //重点：这个查询支持通过Example类指定查询列，通过selectProperties方法指定查询列
        return mapper.selectByExample(example);
    }
}

4.4 创建自定义Service

UserService接口：

import com.suruomo.springboot10mybatis.model.User;
import com.suruomo.springboot10mybatis.service.common.IService;

/**
 * @author suruomo
 * @date 2020/7/29 13:30
 * @description:
 */
public interface UserService extends IService<User> {
}

实现类：

import com.suruomo.springboot10mybatis.mapper.UserMapper;
import com.suruomo.springboot10mybatis.model.User;
import com.suruomo.springboot10mybatis.service.common.BaseService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import tk.mybatis.mapper.common.Mapper;

/**
 * @author suruomo
 * @date 2020/7/29 13:31
 * @description:
 */
@Repository("userService")
public class UserServiceImpl extends BaseService<User> implements UserService{
}

4.5 测试

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.suruomo.springboot10mybatis.model.User;
import com.suruomo.springboot10mybatis.service.UserService;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import tk.mybatis.mapper.entity.Example;

import javax.annotation.Resource;
import java.util.ArrayList;
import java.util.List;

/**
 * 测试
 */
@SpringBootTest
class Springboot10MybatisApplicationTests {

    @Resource
    private UserService userService;

    /**
     * 通用mapper的插入测试
     */
    @Test
    void save() {
        User user = new User();
        user.setUserId("susu");
        user.setUserName("suruomo");
        user.setEmail("1232@qq.com");
        user.setSex("1");
        user.setPassword("xMpCOKC5I4INzFCab3WEmw==");
        userService.save(user);
    }

    /**
     * 通用mapper的删除测试
     */
    @Test
    void delete() {
        User user = new User();
        user.setUserId("susu");
        this.userService.delete(user);
    }

    /**
     * 通用mapper的查询单个测试
     */
    @Test
    void select(){
        String userId="a";
        System.out.println(userService.selectByKey(userId).getEmail());
    }

    /**
     * 通用mapper的查询全部测试
     */
    @Test
    void selectAll(){
        List<User> list=new ArrayList<>();
        list=userService.selectAll();
        for(User user:list){
            System.out.println(user.getUserId());
        }
    }

    /**
     * 通用mapper的example自定义查询
     */
    @Test
    void selectByExample(){
        Example example = new Example(User.class);
        example.createCriteria().andCondition("user_name like '%a%'");
        List<User> userList = this.userService.selectByExample(example);
        for (User u : userList) {
            System.out.println(u.getUserName());
        }
    }

    /**
     * 通用mapper的更改
     */
    @Test
    void updateAll(){
        User user=userService.selectByKey("zxc");
        user.setLoginIp("127.0.0.1");
        userService.updateAll(user);
    }

    /**
     * 分页查询
     */
    @Test
    void selectByPage(){
        PageHelper.startPage(1 ,2);
        List<User> list = userService.selectAll();
        PageInfo<User> pageInfo = new PageInfo<User>(list);
        List<User> result = pageInfo.getList();
        for (User u : result) {
            System.out.println(u.getUserName());
        }
    }

    /**
     * 自定义mapper查询
    */
    @Test
    void selectByUserName(){
        String userName="b";
        System.out.println(userService.selectByUserName(userName));
    }

}