Mybatis学习笔记12 - 动态sql之choose(when otherwise)标签

choose (when, otherwise):分支选择；带了break的swtich-case

示例代码：

接口定义：
package com.mybatis.dao;

import com.mybatis.bean.Employee;

import java.util.List;

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

mapper定义：
<?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.mybatis.dao.EmployeeMapper">
    <!--
        choose (when, otherwise):分支选择；带了break的swtich-case
	    如果带了id就用id查，如果带了lastName就用lastName查,只会进入其中一个
	 -->
    <select id="getEmpsByConditionChoose" resultType="com.mybatis.bean.Employee">
        select * from tbl_employee
        <where>
            <choose>
                <when test="id!=null">
                    id=#{id}
                </when>
                <when test="lastName!=null">
                    last_name like #{lastName}
                </when>
                <when test="email!=null">
                    email=#{email}
                </when>
                <otherwise>
                    gender=0
                </otherwise>
            </choose>
        </where>
    </select>
</mapper>

测试代码：
package com.mybatis.demo;

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

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

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

    @Test
    public void test() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession openSession = sqlSessionFactory.openSession(true);
        try {
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
            List<Employee> emps = mapper.getEmpsByConditionChoose(new Employee(1, "%t%", null, null));
            for (Employee emp : emps) {
                System.out.println(emp);
            }
        } finally {
            openSession.close();
        }
    }
}