mybatis-210721-07---动态sql-内置参数_parameter_databaseId&bind使用

mybatis-210721-07—动态sql-内置参数_parameter_databaseId&bind

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

---

EmployeeMapper.java

package com.bgy.mybatis.dao;

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

public interface EmployeeMapper {
	
	public List<Employee> getEmpsTestInnerParameter(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">
	
	<!--
		mybatis中默认的两个内置参数：
			_parameter:
				代表整个参数
				单个参数：_parameter就是这个参数
				多个参数：参数会被封装为一个map，_parameter就代表这个map
			
			_databaseId：
				如果配置了databaseIdProvider标签
				_databaseId就代表当前数据库的别名oracle/mysql/...
	-->
	
	<select id="getEmpsTestInnerParameter" resultType="com.bgy.mybatis.bean.Employee">
		
		<!--
			bind:
				可以将OGNL表达式的值绑定到一个变量中，方便后来引用这个变量的值
				
				把value的值赋给name，可以拼接字符串
		-->
		<bind name="_lastName" value="'%'+lastName+'%'"/>
		
		<if test="_databaseId=='mysql'">
			select 
				*
			from
				tbl_employee
			<if test="_parameter!=null">
				where
					last_name like #{_lastName}
			</if>
		</if>
		<if test="_databaseId=='oracle'">
			select 
				*
			from
				tbl_employee
			<if test="_parameter!=null">
				where
					last_name=#{_parameter.lastName}
			</if>
		</if>
	</select>
</mapper>

MybatisTest.java

package com.bgy.mybatis.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
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.Department;
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——内置参数-parameter&databaseId和bind的使用
	 * @throws IOException
	 */
	@Test
	public void test() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession sqlSession = sqlSessionFactory.openSession();
		
		try {
			EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
			
			List<Employee> list = mapper.getEmpsTestInnerParameter(new Employee(null,"a","",""));
			
			System.out.println(list);
		} finally {
			sqlSession.close();
		}
	}
	
}