参数传递
单个字面量类型的参数
在mapper接口中使用单个参数,直接使用#{}或者${}在映射文件中接收,注意${}本质是字符串拼接,因此在接收字符型的数据使用单引号括起来,#{}本质为占位符.
eg:
mapper接口:
package com.mappers;
import com.pojo.User;
public interface UserMapper {
User selectUserById(int userid);
User selectUserByName(String username);
}
映射文件:
mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mappers.UserMapper">
<select id="selectUserById" resultType="user">
select * from user where userid=#{userid}
select>
<select id="selectUserByName" resultType="User">
select * from user where username='${username}'
select>
mapper>
调用方法时直接传参:
selectUserByName("张三");
selectUserById(2);
接口方法参数有多个
这时系统会将参数放入Map集合中,以两种方式进行存储
- 以arg0,arg1....为键,传入的参数为值
- 以param1,param2...为键,传入的参数为值
因此在映射文件中访问可以通过#{}或者${}写入对应键进行访问
mapper接口:
package com.mappers;
import com.pojo.User;
public interface UserMapper {
User selectUserByIdAndName(int userid,String username);
}
映射文件:
方式2:
使用map作为参数进行传递多个参数
mapper接口:
package com.mappers;
import com.pojo.User;
import java.util.Map;
public interface UserMapper {
User selectUserByIdAndName(Map map) ;
}
映射文件:
<select id="selectUserByIdAndName" resultType="User">
select * from user where userid=#{userid} and username=#{username}
select>
调用:先定义好map,再进行调用
Map map=new HashMap<>();
map.put("userid",2);
map.put("username","李四");
User user3=userMapper.selectUserByIdAndName(map);
方式3:(推荐)
使用@Param("")注解,本质也是放到Map集合里,知识我们规定了键名,在使用时直接通过指定的键名访问,在注解的参数里写入我们指定的键名
mapper接口:
package com.mappers;
import com.pojo.User;
public interface UserMapper {
User selectUserByIdAndName(@Param("userid") int userid, @Param("username") String username);
}
映射文件:
<select id="selectUserByIdAndName" resultType="User">
select * from user where userid=#{userid} and username=#{username}
select>
传入参数为实体类对象
直接通过#{}或${}和属性名对各个属性值进行使用
mapper接口
package com.mappers;
import com.pojo.User;
public interface UserMapper {
int insertUser(User user);
}
映射文件:使用时通过类内属性名即可访问
<insert id="insertUser">
insert into user values (null,#{username},#{userpass},#{usertel},#{usercard});
insert>
调用:先定义,然后传入使用
User user4=new User(1,"哈哈","aiw","159",10);
userMapper.insertUser(user4);