Mybatis参数传递

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:

 <?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"> <!--第一个一致,对应Mapper接口--> <mapper namespace="com.mappers.UserMapper">      <!--第二个一致,对应方法名    User selectUserById(int userid); -->   <select id="selectUserById" resultType="user">         select * from user where userid=#{userid}   </select>      <!--User selectUserByName(String username);-->     <select id="selectUserByName" resultType="User">         select * from user where username='${username}'     </select> <!--     select * from user where username=#{username}-->   </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

1. 以arg0,arg1....为键,传入的参数为值
2. 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:

  <!-- User selectUserByIdAndName(int userid,String username);-->     <select id="selectUserByIdAndName" resultType="User">         select * from user where userid=#{arg0} and username=#{arg1}        <!--或者 select * from user where userid=#{param1} and username=#{param2}-->     </select>  

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<String, Object> 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<String,Object> 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

 <!--    int insertUser(User user);-->     <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);