Mybatis注解开发

一、MyBatis的常用注解类型

package com.ithiema.Dao;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class User {
    private int id;
    private String username;
    private String password;
    private String perms;
}

package com.ithiema.Mapper;

import com.ithiema.Dao.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

public interface UserMapper {
@Insert("INSERT INTO user(username,password,perms) VALUES(#{username},#{password},#{perms})")
    public void save(User user);

    @Select("SELECT * FROM user")
    public List<User> findAll();

    @Select("SELECT id,username,password,perms FROM user WHERE id = #{id}")
    public User findById(int id);

    @Delete("DELETE FROM user WHERE id=#{id}")
    public void delete(int id);

    @Update("UPDATE user SET username=#{username},password=#{password},perms=#{perms} WHERE id=#{id}")
    public void update(User user);
}

driver=com.mysql.cj.jdbc.Driver
username=root
password=admin
url=jdbc:mysql://localhost:3306/dbstudy?useSSL=false&serverTimezone=Asia/Shanghai&allowPublicKeyRetrieval=true

<?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>
    <!-- 顺序不能乱：properties -> settings -> typeAliases -> typeHandlers -> environments -> mappers -->

    <!-- 1.加载外部properties数据库配置文件 -->
    <properties resource="jdbc.properties">
        <!-- 也可以直接写property -->
    </properties>

    <!-- 2.全局设置 -->
    <settings>
        <setting name="logImpl" value="SLF4J"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!-- 3.起别名，简化mapper中实体类全限定名 -->
    <typeAliases>
        <typeAlias type="com.ithiema.Dao.User" alias="user"></typeAlias>
    </typeAliases>

    <!-- 4.多环境配置，default指定使用哪个环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 5.注册Mapper映射文件（核心！） -->
    <mappers>
        <!-- 方式1：resource加载xml -->
<!--        <mapper resource="com.ithiema.mapper/UserMapper.xml"/>-->
        <!-- 方式2：扫描整个包，接口名和xml同名同路径 -->
         <package name="com.ithiema.Mapper"/>
    </mappers>
</configuration>

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.itheima</groupId>
  <artifactId>Mybatis_anno</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>Mybatis_anno Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>

      <!-- MyBatis核心包 -->
      <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.5.19</version>
      </dependency>

      <!-- MySQL8驱动 -->
      <dependency>
          <groupId>com.mysql</groupId>
          <artifactId>mysql-connector-j</artifactId>
          <version>8.3.0</version>
      </dependency>

      <!-- logback，SLF4J实现，不用log4j -->
      <dependency>
          <groupId>ch.qos.logback</groupId>
          <artifactId>logback-classic</artifactId>
          <version>1.2.11</version>
      </dependency>


      <!-- Junit4 测试用（可选，写单元测试） -->
      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.13.2</version>
          <scope>test</scope>
      </dependency>
      <dependency>
          <groupId>org.projectlombok</groupId>
          <artifactId>lombok</artifactId>
          <version>1.18.46</version>
          <scope>provided</scope>
      </dependency>

  </dependencies>
  <build>
    <finalName>Mybatis_anno</finalName>
  </build>
</project>

二、注解实现复杂映射开发

一对一查询的两种方式

package com.ithiema.Mapper;

import com.ithiema.Dao.Order;
import com.ithiema.Dao.User;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface OrderMapper {
    @Select("select *,o.id oid from orders o,user u where o.uid=u.id")
//    @Results({
//            @Result(column = "oid", property = "id"),
//            @Result(column = "total", property = "total"),
//            @Result(column = "uid", property = "user.id"),
//            @Result(column = "username", property = "user.username"),
//            @Result(column = "password", property = "user.password"),
//    })
    @Results({
            @Result(column = "oid", property = "id"),
            @Result(column = "total", property = "total"),
            @Result(
                    property = "user",//要封装的属性的名称
                    column = "uid",//根据哪个字段去查询user表的数据
                    javaType = User.class,//要封装的实体类型
                    //select属性，代表  查询 的哪个接口的方法获得数据
                    one = @One(select = "com.ithiema.Mapper.UserMapper.findById")
            )

    })
    public List<Order> findAll();

}

一对多查询

package com.ithiema.Mapper;

import com.ithiema.Dao.Order;
import com.ithiema.Dao.User;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface OrderMapper {
    @Select("select *,o.id oid from orders o,user u where o.uid=u.id")
//    @Results({
//            @Result(column = "oid", property = "id"),
//            @Result(column = "total", property = "total"),
//            @Result(column = "uid", property = "user.id"),
//            @Result(column = "username", property = "user.username"),
//            @Result(column = "password", property = "user.password"),
//    })
    @Results({
            @Result(column = "oid", property = "id"),
            @Result(column = "total", property = "total"),
            @Result(
                    property = "user",//要封装的属性的名称
                    column = "uid",//根据哪个字段去查询user表的数据
                    javaType = User.class,//要封装的实体类型
                    //select属性，代表  查询 的哪个接口的方法获得数据
                    one = @One(select = "com.ithiema.Mapper.UserMapper.findById")
            )

    })
    public List<Order> findAll();

    @Select("select * from orders where uid=#{uid}")
    public List<Order> findByUid(int uid);
}

OrderMapper加一句以供调用

@Select("select * from orders where uid=#{uid}")
public List<Order> findByUid(int uid);

package com.ithiema.Mapper;

import com.ithiema.Dao.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserMapper {
@Insert("INSERT INTO user(username,password,perms) VALUES(#{username},#{password},#{perms})")
    public void save(User user);

    @Select("SELECT * FROM user")
    public List<User> findAll();

    @Select("SELECT id,username,password,perms FROM user WHERE id = #{id}")
    public User findById(int id);

    @Delete("DELETE FROM user WHERE id=#{id}")
    public void delete(int id);

    @Update("UPDATE user SET username=#{username},password=#{password},perms=#{perms} WHERE id=#{id}")
    public void update(User user);

    @Select("select * from user")
    @Results({
            @Result( id=true, property = "id", column = "id"),//id=true表明是主键id
            @Result(column = "username",property = "username"),
            @Result(column = "password", property = "password"),
            @Result(
                    property = "orderList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.ithiema.Mapper.OrderMapper.findByUid")
            )
    })
    public List<User> findUserAndOrder(String username);
}

多对多查询

图表见下方链接：https://blog.csdn.net/m0_57532232/article/details/164811038?spm=1001.2014.3001.5501

    @Select("select * from user")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "roleList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.ithiema.Mapper.RoleMapper.findByUid")
            )
    })
    public List<User> findUserAndRole

package com.ithiema.Mapper;

import org.apache.ibatis.annotations.Select;

public interface RoleMapper {

    @Select("select * from sys_user_role ur,sys_role r where ur.roleId=r.id AND ur.userId=#{uid}")
    public List<Role> findByUid();
}

相对于一对多，一对一的查询，一对多查询多了一张中间表，即：将userid 与 roleid 对应的中间表。先将中间表和职能表进行链接得出内容再与user表进行链接。

posted @ 2026-09-24 12:32 吴中正Kevin 阅读(6) 评论(0) 收藏举报

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棱镜PrismK(观自在)

Mybatis注解开发

一、MyBatis的常用注解类型

二、注解实现复杂映射开发

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