Mybatis 笔记——输入参数输出参数

Posted 2021-05-17 Johnny*

输入参数、输出参数

• 输入参数
• • 简单类型
  • 对象类型
  • #{}和 ${}的区别
• 存储过程的调用
• 输出参数

输入参数

简单类型

#{任意值}
${value},占位符只能是value

对象类型

1. 获取对象值
   #{对象属性}
   ${对象属性}

select name, age from person where perSex = #{sex} or name like #{name}

java中：
Person per = new Person();
per.setSex(1);
per.setName("%z%");
List<Person > persons = personMapper.queryPersonBySexOrName(per )

或者使用${}

select name, age from person where perSex = ${sex} or name like '%${name}%'

java中：
Person per = new Person();
per.setSex(1);
per.setName("z");
List<Person > persons = personMapper.queryPersonBySexOrName(per )

	<!-- 输入参数为 级联属性 -->
	<select id="queryStudentByaddress" 	parameterType="student"	resultType="student" > 
		select stuno,stuname,stuage  from student where homeaddress = #{address.homeAddress}  or schooladdress = '${address.schoolAddress}'
	</select>

2. 输入对象为HashMap

#{}和 ${}的区别

1. 用法
   #{}类型转换，自动给String类型加上’’
   ${} 原样输出，但是适合动态排序

select name,age from person where id= #{value}
select name,age from person where id = '${value}'

动态排序

select name,age from person Order by ${value} desc

2. 安全性

#{} 可以防止SQL注入
${}不能

存储过程的调用

1. 查询男/女的人数
   输入： 性别（男：1； 女：0）
   输出：人数

CREATE DEFINER=`root`@`localhost` PROCEDURE `selectPerBySexProcedure`(in sex int, out num int)
begin
select count(*) into num from person where person.perSex = sex;
end

存储过程应用SELECT 语句从person 表中获取person.perSex = sex的记录总数。最后将结果传递给变量num 。

<select id="selectPersonBySexProcedure"  parameterType="HashMap" statementType="CALLABLE">
	 	{
	 		CALL selectPerBySexProcedure(
	 			#{mySex,jdbcType=INTEGER,mode=IN},
	 			#{perCount, jdbcType=INTEGER,mode=OUT}
	 		)
	 	
	 	} 
	 </select>

	public static void selectPersonBySexProcedure() throws IOException {
		InputStream in = Resources.getResourceAsStream("config.xml");
		SqlSessionFactory sqlFactory =  new SqlSessionFactoryBuilder().build(in);
		
		SqlSession session = sqlFactory.openSession();
		
		PersonMapper personMapper = session.getMapper(PersonMapper.class);
		Map<String, Object> map = new HashMap<>();
		map.put("mySex", 1);//xml中mySex占位符
		personMapper.selectPersonBySexProcedure(map);
		int count = (int)map.get("perCount");//由于存储过程没有返回值 通过out参数来获得
		System.out.println(count);
	}

其中 通过statementType="CALLABLE"设置SQL的执行方式是存储过程。 存储过程的输入参数sex需要通过HashMap（即key=mySex）来指定
在使用时，通过hashmap的put方法传入输入参数的值；通过hashmap的Get方法 获取输出参数的值。

2. 按id删除指定人

创建存储过程deletePersonByIdProcedure

CREATE DEFINER=`root`@`localhost` PROCEDURE `deletePersonByIdProcedure`(in id int)
begin
delete from person where person.id = id;
end

public static void deletePersonByIdProcedure() throws IOException {
		InputStream in = Resources.getResourceAsStream("config.xml");
		SqlSessionFactory sqlFactory =  new SqlSessionFactoryBuilder().build(in);
		
		SqlSession session = sqlFactory.openSession();
		
		PersonMapper personMapper = session.getMapper(PersonMapper.class);
		Map<String, Object> map = new HashMap<>();
		map.put("id", 3);
		personMapper.deletePersonByIdProcedure(map);
		session.commit();
	}

	 <delete id="deletePersonByIdProcedure" parameterType ="HashMap" statementType="CALLABLE">
	 	{
	 		CALL deletePersonByIdProcedure(
	 			#{id, jdbcType=INTEGER, mode=IN}
	 		)
	 	}
	 	
	 </delete>

输出参数

1. 简单类型（8个基本+String）
2. 输出参数为实体对象类型
3. 输出参数为实体对象类型的集合 ：虽然输出类型为集合，但是resultType依然写 集合的元素类型（resyltType=“Person”）
4. 输出参数为HashMap

	 <!-- 别名（不要求与属性名一致 只做mapkey时使用）作为map的key -->
	 <select id="selectAllPersonWithHashMap" resultType="HashMap"> 
	 	select id 'id', name 'perName', age 'perAge', perSex 'sex' from person
	 </select>

	public static void selectAllPersonWithHashMap() throws IOException {
		InputStream in = Resources.getResourceAsStream("config.xml");
		SqlSessionFactory sqlFactory =  new SqlSessionFactoryBuilder().build(in);
		SqlSession session = sqlFactory.openSession();
		PersonMapper personMapper = session.getMapper(PersonMapper.class);
		List<Map<String, Object>> allPerson = personMapper.selectAllPersonWithHashMap();
		for(Map<String,Object> perMap: allPerson)
			System.out.println(perMap);
	}

输出结果

{perAge=22, perName=johnny, sex=0, id=1}
{perAge=98, perName=weiwei, sex=1, id=2}
{perAge=11, perName=j简单, sex=0, id=52}

5. 使用resultMap指定输出类型及映射关系
   当属性名 和字段名 不一致时，除了使用resultMap以外，还可以使用resultType+HashMap
   使用resultMap

	<resultMap type="person" id="queryPersonByIdMap">
			<!-- 指定类中的属性 和 表中的字段 对应关系 -->
			<id property="perNo"  column="id" />
			<result property="perName" column="name" />
	</resultMap>

使用Map的集合

别名作为map的key

personMapper.xml

	 <!-- 别名作为map的key -->
	 <select id="selectAllPersonWithHashMap" resultType="HashMap"> 
	 	select id 'id', name 'perName', age 'perAge', perSex 'sex' from person
	 </select>

接口

List<Map<String, Object>> selectAllPersonWithHashMap();

测试类：

	public static void selectAllPersonWithHashMap() throws IOException {
		InputStream in = Resources.getResourceAsStream("config.xml");
		SqlSessionFactory sqlFactory =  new SqlSessionFactoryBuilder().build(in);
		SqlSession session = sqlFactory.openSession();
		PersonMapper personMapper = session.getMapper(PersonMapper.class);
		List<Map<String, Object>> allPerson = personMapper.selectAllPersonWithHashMap();
		for(Map<String,Object> perMap: allPerson)
			System.out.println(perMap);
	}

另一种左边表中字段名 右边属性名
personMapper.xml

	 <!-- 左边表中字段名 右边属性名 -->
	 <select id="selectAllPersonByHashMap" resultType="person"> 
	 	select id 'id', name 'name', age 'age', perSex 'sex' from person 
	 </select>

接口

List<Person> selectAllPersonByHashMap();

测试：

	public static void selectAllPersonByHashMap() throws IOException {
		InputStream in = Resources.getResourceAsStream("config.xml");
		SqlSessionFactory sqlFactory =  new SqlSessionFactoryBuilder().build(in);
		SqlSession session = sqlFactory.openSession();
		PersonMapper personMapper = session.getMapper(PersonMapper.class);
		List<Person> allPerson = personMapper.selectAllPersonByHashMap();
		for(Person per: allPerson)
			System.out.println(per);
	}