MyBatis快速入门——第二章、参数传递demo(id查询&模糊查询)

红目香薰

发布于 2022-11-30 15:15:14

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发布于 2022-11-30 15:15:14

文章被收录于专栏：CSDNToQQCode

MyBatis快速入门——第二章、参数传递demo(id查询&模糊查询)

1、前置环境

MyBatis快速入门——第一章、idea的maven配置与demo实例

2、创建【com.item.mapper.模型Mapper.java】文件

创建位置

编码：

@Param("传递参数标识符")

package com.item.mapper;

import com.item.model.Users;
import org.apache.ibatis.annotations.Param;

public interface UsersMapper {
    /**
     * 根据id查询
     * @param id
     * @return
     */
    Users SelectById(@Param("id")int id);
    /**
     * 根据id查询
     * @param nickName
     * @return
     */
    Users SelectByName(@Param("nickName")String nickName);

}

3、修改【模型Mapper.xml】配置文件

#和$两者含义不同

【#】会把传入的数据都当成一个字符串来处理，会在传入的数据上面加一个双引号来处理。

【$】则是把传入的数据直接显示在sql语句中，不会添加双引号。

<?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.item.mapper.UsersMapper">
    <select id="GetInfo" resultType="Users">
        select * from users
    </select>
    <select id="SelectById" resultType="Users" parameterType="java.lang.Integer">
        select * from users where id=#{id}
    </select>
    <select id="SelectByName" resultType="Users" parameterType="java.lang.String">
        select * from users where nickName like "%${nickName}%"
    </select>
</mapper>

4、测试

测试编码:

package com.item.action;

import com.item.mapper.UsersMapper;
import com.item.model.Users;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.Reader;

public class Action {
    public static void main(String[] args) throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession sqlSession = sessionFactory.openSession();
        UsersMapper db = sqlSession.getMapper(UsersMapper.class);

        Users users = db.SelectById(2);
        Sout(users);
        Users users1 = db.SelectByName("龙");
        Sout(users1);
        sqlSession.close();
    }

    /**
     * 输出用
     * @param users
     */
    public static void Sout(Users users){
        System.out.println("编号:"+users.getId());
        System.out.println("创建时间:"+users.getCreateDate());
        System.out.println("昵称:"+users.getNickName());
        System.out.println("性别:"+(users.getSex()==0?"女":"男"));
        System.out.println("年龄:"+users.getAge());
        System.out.println("简介:"+users.getIntroduce());
    }

}

测试成功：

5、多表联合查询测试

在【模型Mapper.xml】配置文件中添加

    <select id="GetUserInfo" resultType="UserInfo">
        select
        users.id,
        users.createDate,
        users.nickName,
        users.sex,
        users.age,
        users.introduce,
        userInfo.uid,
        userInfo.phone
        from users inner join userInfo on users.id=userInfo.uid
    </select>

由于没有【UserInfo】类，需要在【model】下创建，为了测试方便，我只添加了【phone】列

package com.item.model;

public class UserInfo extends Users{
    private int uid;
    private String phone;

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

在【com.item.mapper.UserMapper.java】文件中添加【查询所有的方法】

package com.item.mapper;

import com.item.model.UserInfo;
import com.item.model.Users;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface UsersMapper {
    /**
     * 查询所有
     * @return
     */
    List<UserInfo> GetUserInfo();

    /**
     * 根据id查询
     * @param id
     * @return
     */
    Users SelectById(@Param("id")int id);
    /**
     * 根据id查询
     * @param nickName
     * @return
     */
    Users SelectByName(@Param("nickName")String nickName);

}

由于没有参数，直接遍历就行：

package com.item.action;

import com.item.mapper.UsersMapper;
import com.item.model.UserInfo;
import com.item.model.Users;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.Reader;
import java.util.List;

public class Action {
    public static void main(String[] args) throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession sqlSession = sessionFactory.openSession();
        UsersMapper db = sqlSession.getMapper(UsersMapper.class);

        List<UserInfo> userInfos = db.GetUserInfo();
        for (UserInfo u:userInfos) {
            Sout(u);
        }
    }

    /**
     * 输出用
     * @param users
     */
    public static void Sout(UserInfo users){
        System.out.println("编号:"+users.getId());
        System.out.println("创建时间:"+users.getCreateDate());
        System.out.println("昵称:"+users.getNickName());
        System.out.println("性别:"+(users.getSex()==0?"女":"男"));
        System.out.println("年龄:"+users.getAge());
        System.out.println("简介:"+users.getIntroduce());
        System.out.println("手机:"+users.getPhone());
    }

}

本章内容只针对简单的【DQL】语句进行训练，后面内容会做相应的【DML】语句操作。

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原始发表：2022-05-27，如有侵权请联系 cloudcommunity@tencent.com 删除

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