mybatis-210721-03---动态sql-choose分支选择

mybatis-210721-03—动态sql-choose分支选择

• EmployeeMapper.java
• EmployeeMapper.xml(笔记在这儿哦)
• MybatisTest.java

---

<!--
		查询员工
			要求：
			携带了那个字段，查询条件就带上这个字段的值
-->

EmployeeMapper.java

package com.bgy.mybatis.dao;

import java.util.List;
import com.bgy.mybatis.bean.Employee;

public interface EmployeeMapper {
	
	public List<Employee> getEmpsByConditionChoose(Employee employee);
}

EmployeeMapper.xml(笔记在这儿哦)

<?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.bgy.mybatis.dao.EmployeeMapper">
	
	<!--
		choose（when，otherwise）
			分支选择（switch-case）
			如果带了id就用id查，如果带了lastName就用lastName查
			只会进入一个
	-->
	<!--
		查询员工
			要求：
			携带了那个字段，查询条件就带上这个字段的值
	-->
	<select id="getEmpsByConditionChoose" resultType="com.bgy.mybatis.bean.Employee">
		select 
			* 
		from
			tbl_employee
			<where>
				<choose>
					<when test="id!=null and id!=''">
						id=#{id}
					</when>
					<when test="lastName!=null and lastName!=&quot;&quot;">
						last_name like #{lastName}
					</when>
					<when test="email!=null and email.trim()!=&quot;&quot;">
						email like #{email}
					</when>
					<when test="gender==0 or gender==1">
						gender=#{gender}
					</when>
					<otherwise>
						1=1
					</otherwise>
				</choose>
			</where>
	</select>
</mapper>

MybatisTest.java

package com.bgy.mybatis.test;

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

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 org.junit.jupiter.api.Test;

import com.bgy.mybatis.bean.Employee;
import com.bgy.mybatis.dao.EmployeeMapper;

class MybatisTest {
	
	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}

	
	/**
	 * 测试sql——choose分支选择
	 * @throws IOException
	 */
	@Test
	public void test() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession sqlSession = sqlSessionFactory.openSession();
		
		try {
			EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
			
			Employee employee = new Employee(null,null,null,null);
			List<Employee> emps = mapper.getEmpsByConditionChoose(employee);
			
			System.out.println(emps);
		} finally {
			sqlSession.close();
		}
	}
}