MyBatis——（5）MyBatis_映射配置文件_参数处理

1,单个参数：mybatis不会做特殊处理

#{参数名/任意名}：取出参数值。

按照MyBatis——（5）MyBatis_映射配置文件_增删改查以及获取自增主键值
的思路
我们只需要修改EmployeeMapper.java和EmployeeMapper.xml和测试类MyBatisTest.java即可

EmployeeMapper.java

public interface EmployeeMapper {
	public Employee getEmpByName(String name);
}

EmployeeMapper.xml

<?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.atstudying.mybatis.dao.EmployeeMapper">
<!-- 
 <!-- 	public Employee getEmpByName(String name); -->
    <select id="getEmpByName" resultType="com.atstudying.mybatis.bean.Employee">
        select * from employee where lastName=#{1};
    </select>
>

MyBatisTest.java

@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//单个参数
			Employee employee=mapper.getEmpByName("zlj");
			System.out.println(employee);
		}finally{
			openSession.close();
		}
	}

结果

结果我们知道在EmployeeMapper.xml中的查询语句中无论#[]中的值是否是EmployeeMapper.java中传入参数的值，仍然可以查询到结果，因为单个参数：mybatis不会做特殊处理

2，多个参数：mybatis会做特殊处理。

多个参数会被封装成 一个map，
key：param1…paramN,或者参数的索引也可以
value：传入的参数值
#{}就是从map中获取指定的key的值；

EmployeeMapper.java

public interface EmployeeMapper {
	public Employee getEmpByIdAndLastName1(Integer id,String lastName);
	public Employee getEmpByIdAndLastName2(@Param("id")Integer id,@Param("lastName")String lastName);
	public Employee getEmpByIdAndLastName3(Integer id,String lastName);

}

EmployeeMapper.xml

<?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.atstudying.mybatis.dao.EmployeeMapper">
	<!--  public Employee getEmpByIdAndLastName1(Integer id,String lastName);-->
 	<select id="getEmpByIdAndLastName1" resultType="com.atguigu.mybatis.bean.Employee">
 		select * from employee where id = #{id} and last_name=#{lastName}
 	</select>
 	<!--  public Employee getEmpByIdAndLastName2(Integer id,String lastName);-->
 	<select id="getEmpByIdAndLastName2" resultType="com.atguigu.mybatis.bean.Employee">
 		select * from employee where id = #{id} and last_name=#{lastName}
 	</select>
 	<!--  public Employee getEmpByIdAndLastName3(Integer id,String lastName);-->
 	<select id="getEmpByIdAndLastName3" resultType="com.atguigu.mybatis.bean.Employee">
 		select * from employee where id = #{param1} and last_name=#{param2}
 	</select>
>

MyBatisTest.java

@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//多个参数
			Employee employee2=mapper.getEmpByIdAndLastName2(1, "zlj");
			System.out.println(employee2);

			Employee employee3=mapper.getEmpByIdAndLastName3(1, "zlj");
			System.out.println(employee3);

			Employee employee1=mapper.getEmpByIdAndLastName1(1, "zlj");
			System.out.println(employee1);
		}finally{
			openSession.close();
		}
	}

结果

结果可知道多个参数传进，多个参数会被封装成 一个map
key——》param1…paramN,或者参数的索引也可以
value——》：传入的参数值（#{param1}）
#{}就是从map中获取指定的key的值；
多个参数：mybatis会做特殊处理

异常：
org.apache.ibatis.binding.BindingException:
Parameter ‘id’ not found.
Available parameters are [1, 0, param1, param2]
操作：
方法： public Employee getEmpByIdAndLastName1(Integer id,String lastName);
取值：#{id},#{lastName}
如上操作就会报上述异常

3,命名参数 ：明确指定封装参数时map的key；@Param(“id”)

多个参数会被封装成 一个map，
key：使用@Param注解指定的值
value：参数值
#{指定的key}取出对应的参数值
在上述中已经提到代码演示，这里不再赘述

4，POJO

如果多个参数正好是我们业务逻辑的数据模型，我们就可以直接传入pojo；
#{属性名}：取出传入的pojo的属性值

EmployeeMapper.java

public interface EmployeeMapper {
//以下测试POJO演示
	public Employee getEmpByPOJO(Employee employee);

EmployeeMapper.xml

<?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.atstudying.mybatis.dao.EmployeeMapper">
<!--  以下测试POJO演示-->
 	<!-- public Employee getEmpByPOJO(Employee employee); -->
 	<select id="getEmpByPOJO" resultType="com.atguigu.mybatis.bean.Employee">
 		select * from employee where id=${id} and lastName=#{lastName}
 	</select>
>

MyBatisTest.java

@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//POJO演示
			Employee employee=new Employee(1,"zlj","[email protected]","add");
			Employee employee2=mapper.getEmpByPOJO(employee);
			System.out.println(employee2);
		}finally{
			openSession.close();
		}
	}

结果

结果说明，如果多个参数正好是我们业务逻辑的数据模型，我们就可以直接传入pojo；
#{属性名}：取出传入的pojo的属性值

5，Map

如果多个参数不是业务模型中的数据，没有对应的pojo，不经常使用，为了方便，我们也可以传入map
#{key}：取出map中对应的值

EmployeeMapper.java

public interface EmployeeMapper {
//以下测试Map演示
	public Employee getEmpByMap(Map<String, Object> map);}

EmployeeMapper.xml

<?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.atstudying.mybatis.dao.EmployeeMapper">
<!--  以下测试Map演示-->
 	<!-- public Employee getEmpByMap(Map<String, Object> map); -->
 	<select id="getEmpByMap" resultType="com.atguigu.mybatis.bean.Employee">
 		select * from ${tableName} where id=${id} and last_name=#{lastName}
 	</select>
>

MyBatisTest.java

@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//Map演示
			Map<String, Object> map = new HashMap<>();
			map.put("id", 2);
			map.put("lastName", "Tom");
			map.put("tableName", "employee");
			Employee employee = mapper.getEmpByMap(map);
			
			System.out.println(employee);
		}finally{
			openSession.close();
		}
	}

结果

结果说明我们成功传入了map的值，#{key}：取出map中对应的值

6，参数值的获取

MyBatis——小知识：MyBatis_映射配置文件_参数值获取

7，#{}:更丰富的用法

MyBatis——小知识：MyBatis_映射配置文件_#{}:更丰富的用法：