04_通用mapper

张创琦 2022.03.11

避免重复书写CRUD映射的框架有两个

• 通用mybatis（tk mybatis）

• mybatis plus，通能更加强大，后面实战项目中讲解

1 tk mybatis

1. pom.xml 配置文件

<!-- 通用mapper -->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>2.0.2</version>
        </dependency>

1. 实体类配置

@Table(name = "tb_user") // 表名相关注解
@Column(name="fieldName") // 属性名和字段名的相关注解

package com.lxs.domain;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import java.io.Serializable;
import java.util.Date;
@Table(name = "tb_user") // 如果不声明则默认一样的表名
// 支持驼峰转下划线的命名
public class User implements Serializable {
    // private static final long serialVersionUID = 1L;
    // 主键的映射一定要进行
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) // 逐渐策略是自增
    private Long id;
    // 用户名
    //自动转换下换线到驼峰命名 user_name -> userName
    private String userName;
    // 密码
    private String password;
    // 姓名
    private String name;
    // 年龄
    private Integer age;
    // 性别，1男性，2女性
    private Integer sex;
    // 出生日期
    private Date birthday;
    // 创建时间
    private Date created;
    // 更新时间
    private Date updated;
    // 备注
    private String note;
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", sex=" + sex +
                ", birthday=" + birthday +
                ", created=" + created +
                ", updated=" + updated +
                ", note='" + note + '\'' +
                '}';
    }
    // 省略 getter 和 setter 方法
}

1. UserMapper

一旦继承了Mapper，继承的Mapper就拥有了Mapper所有的通用方法。

具体方法见 pdf 文档

package com.lxs.dao;
import com.lxs.domain.User;
import tk.mybatis.mapper.common.Mapper;
import java.util.List;
// import org.apache.ibatis.annotations.Mapper;
// 注意：在mapper导包时，导入的是tk.mybatis的
public interface UserMapper extends Mapper<User> {
    public List<User> findByUser(User user);
}

注意以下的写法：

package com.lxs.dao;
import com.lxs.domain.User;
//import tk.mybatis.mapper.common.Mapper;
import java.util.List;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface UserMapper extends tk.mybatis.mapper.common.Mapper<User> {
    public List<User> findByUser(User user);
}

1. 映射复杂文件：

resources/mappers/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.lxs.dao.UserMapper">
    <select id="findByUser" resultType="user">
        SELECT * FROM tb_user
        <where>
            <if test="name != null"> name like '%${name}%' </if>
            <if test="note != null"> and note like '%${note}%' </if>
        </where>
    </select>
</mapper>

1. 注意Application的导包问题

一个是 mybatis 的，一个是 tk mybatis 的

// import org.mybatis.spring.annotation.MapperScan; // myBatis的
import org.springframework.boot.SpringApplication; // tk myBatis的
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import tk.mybatis.spring.annotation.MapperScan;
@SpringBootApplication
@EnableConfigurationProperties
@MapperScan("com.lxs.dao")
public class Application {

1. 测试

package com.lxs.dao;
import com.lxs.domain.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import tk.mybatis.mapper.entity.Example;
import java.util.Date;
import java.util.List;
import static org.junit.Assert.*;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
    @Autowired
    private UserMapper userMapper;
    @Autowired
    private UserDao userDao;
    /* chenggong */
    @Test
    public void testFindByUser() {
        User condition = new User();
        condition.setName("a");
        List<User> list = userMapper.findByUser(condition);
        for (User user : list) {
            System.out.println(user);
        }
    }
    /* chenggong
    @Test
    public void testFindAll() {
        userMapper.selectAll().forEach(user -> {
            System.out.println(user);
        });
    }*/
    /* 查询不到userName
    @Test
    public void testFindAll1() {
        List<User> list = userDao.findAll();
        for (User user : list) {
            System.out.println(user);
        }
    }*/
    /* 未测试
    @Test
    public void testFindById() {
        User user = userDao.selectByPrimaryKey(4);
        System.out.println(user);
    }
*/
    /* 测试成功 */
    @Test
    public void testFindByExample() {
        Example example = new Example(User.class);
        example.createCriteria().andLike("name", "%a%");
        userMapper.selectByExample(example).forEach(user -> {
            System.out.println(user);
        });
    }
    /* 未测试
    @Test
    public void testInsert() {
        User user = new User();
        user.setAge(18);
        user.setBirthday(new Date());
        user.setCreated(new Date());
        user.setName("周星驰");
        userDao.insert(user);
    }
*/
}