Mybatis if 标签使用总结，有图易懂

梦里梦外; 2022-10-13 05:23 8阅读 0赞

在项目开发中，mybatis <if> 标签使用广泛，本文讲解if标签的两种使用方式

其一、使用 <if> 标签判断某一字段是否为空

其二、使用 <if> 标签判断传入参数是否相等

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具体代码如下

数据库表结构和数据

![70][]

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实体类：

package com.demo.bean;
     
    public class Commodity {
    	
    	private String name;
    	
    	private String date;
     
    	public String getName() {
    		return name;
    	}
     
    	public void setName(String name) {
    		this.name = name;
    	}
     
    	public String getDate() {
    		return date;
    	}
     
    	public void setDate(String date) {
    		this.date = date;
    	}
     
    	@Override
    	public String toString() {
    		return "Com [name=" + name + ", date=" + date + "]";
    	}
    	
    }

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mapper层：

package com.demo.mapper;
     
    import java.util.List;
    import org.apache.ibatis.annotations.Mapper;
    import org.apache.ibatis.annotations.Param;
    import com.demo.bean.Commodity;
    @Mapper
    public interface CommodityMapper {
     
    	List<Commodity> getListByDate(Commodity commodity);
    	
    	List<Commodity> getListByStartDateAndEndDate(@Param("startDate")String startDate, @Param("endDate")String endDate);
    }

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mapper.xml文件：

<?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.demo.mapper.CommodityMapper">
    	
    	<resultMap id="BaseResultMap" type="com.demo.bean.Commodity">
    		<id column="name" property="name" jdbcType="VARCHAR" />
    		<result column="date" property="date" jdbcType="VARCHAR" />
    	</resultMap>
    	
    	<select id="getListByDate" resultMap="BaseResultMap">
    	  select * from commodity where 1 = 1
    	  <if test="date != null and date != ''">
    	    and date = #{date}
    	  </if> 
    	</select>
    	
    	<select id="getListByStartDateAndEndDate" resultMap="BaseResultMap">
    	  select * from commodity where 1 = 1
    	  <if test="#{startDate}.toString() != #{endDate}.toString()">
    	    and date between #{startDate} and #{endDate}
    	  </if>
    	</select>
    	
    </mapper>

注意:mybatis 等值判断的 tostring()方法 (上边代码中第二个select中的toString()方法)

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controller层：

package com.demo.controller;
     
    import java.util.HashMap;
    import java.util.Map;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    import org.springframework.web.bind.annotation.RestController;
    import com.demo.bean.Commodity;
    import com.demo.mapper.CommodityMapper;
     
    @RestController
    public class DemoController {
     
    	@Autowired
    	private CommodityMapper comMapper;
    	
    	@RequestMapping(value = "/commodity")
    	public Object commodity() {
    		Map<String, Object> map = new HashMap<String, Object>();
    		Commodity com =new Commodity();
    		com.setDate("2018-10-12");
    		map.put("res", comMapper.getListByDate(com));
    		return map;
    	}
    	
    	@RequestMapping(value = "/between")
    	public Object commodityBetween() {
    		Map<String, Object> map = new HashMap<String, Object>();
    		map.put("res", comMapper.getListByStartDateAndEndDate("2018-10-09", "2018-10-13"));
    		return map;
    	}
    }

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测试：

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1、访问  [http://localhost:9000/commodity][http_localhost_9000_commodity]

![70 1][]

2、访问  [http://localhost:9000/between][http_localhost_9000_between]

![70 2][]

[70]: /images/20221005/8935a19796dd48568595660de6ab1a7b.png
[http_localhost_9000_commodity]: http://localhost:9000/commodity
[70 1]: /images/20221005/81a4b9344d514107bcce4a9e516fd555.png
[http_localhost_9000_between]: http://localhost:9000/between
[70 2]: /images/20221005/3a240a244b214c68a2bc8aabb5f846b7.png