mybatis动态sql

mybatis的动态sql：

if标签的使用：

package com.cbh.dao;import java.util.List;import com.cbh.beans.Student;public interface IStudent {List<Student>selectStudentsByCondition(String name,int age,int score);List<Student>selectStudentsByConditionif(Student student);List<Student>selectStudentsByConditionwhere(Student student);}

mapper配置文件

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.cbh.dao.IStudent"><select id="selectStudentsByConditionif" resultType="Student">select id,name,age,score from student1 where 1=1<if test="name !=null and name !=''">and name like '%' #{name} '%'</if><if test="age>0">and age> #{age}</if></select> <select id="selectStudentsByConditionwhere" resultType="Student">select id,name,age,score from student1 <where><if test="name !=null and name !=''">name like '%' #{name} '%'</if><if test="age>0">and age> #{age}</if><if test="score>0">and score>#{score}</if></where></select> <!-- #{}中可以放入的内容1.参数对象的属性2.随意的内容，此时#｛｝是个占位符3.参数为map时的key4.参数为map时，若key所对应的value为对象，则可以将该对象的属性放入5.参数的索引号（本次就是参数的索引号） --> </mapper>

测试类：

package com.cbh.test;import java.util.List;import java.util.Map;import org.apache.ibatis.session.SqlSession;import org.junit.Before;import org.junit.Test;import com.cbh.Utils.MybatisUtils;import com.cbh.beans.Student;import com.cbh.dao.IStudent;public class mytest {private IStudent dao;@Beforepublic void before() {SqlSession sqlSession=MybatisUtils.getSqlSession();dao =sqlSession.getMapper(IStudent.class) ;}@Afterpublic void after(){if(sqlsession!=null）｛sqlsession.close();｝｝@Testpublic void test8(){//Student stu=new Student("大",23,0);Student stu=new Student("",0,0);List<Student> student=dao.selectStudentsByConditionif(stu );for (Student student2 : student) {System.out.println(student2);}}@Testpublic void test9(){Student stu=new Student("",0,100);List<Student> student=dao.selectStudentsByConditionwhere(stu);for (Student student2 : student) {System.out.println(student2);}} }


                                             
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