mybatis中if标签怎么用

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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;} @Overridepublic 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;@Mapperpublic 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; @RestControllerpublic class DemoController { @Autowiredprivate 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

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