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
具体代码如下
数据库表结构和数据
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 + "]"; } }
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); }
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)
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; } }
测试：
1、访问 http://localhost:9000/commodity
2、访问 http://localhost:9000/between
