mybatis映射文件mapper.xml的具体写法

Mapper映射文件是一个xml格式文件，必须遵循相应的dtd文件规范

在学习mybatis的时候我们通常会在映射文件这样写：

    
        select *from student where id=#{id}
    
    
    
        select *from student where gid=#{gid}
    
    
    
        
        
        
            
        
            
        
    

然后再写dao的实现在写一个类，来实现dao的接口。但是这样在实现中需要这样写：

package com.qbd.service;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
 
import com.qbd.mapper.StudentMappers;
import com.qbd.model.Student;
import com.qbd.util.SqlSessionFactoryUtil;
 
public class StudentService {
    private static Logger logge=Logger.getLogger(StudentService.class);
    public static void main(String[] args) {
        SqlSession sqlSession=SqlSessionFactoryUtil.getSqlSession();
        
        StudentMappers studentMappers=(StudentMappers)sqlSession.getMapper(StudentMappers.class);
        Student student=new Student();
        student.setName("22");
        student.setAge(2);
        int s=studentMappers.add(student);
        sqlSession.commit();
        if(s>0){
            logge.info("success");
            System.out.println("success");
        }
        
    }
}

来读取配置文件

另一种方法就是：

直接在mapper.xml中的这一部分写成dao如下

    
    
    
        select * from user
        
            
                and uname like #{uname}
            
        
        
            limit #{start},#{size}
        
    
    
    
        select count(*) from user
        
            
                and uname like #{uname}
            
        
    
    
    
        select *from user where uname=#{uname} and upassword=#{upassword}
    
    
    
        delete from user where uid=#{uid}
    
    
    
        update user
        
            
                 uname=#{uname},
            
            
                upassword=#{upassword},
            
            
                upower=#{upower},
            
        
        where uid=#{uid}
    
    
    
        insert into user values(null,#{uname},#{upassword},#{upower})
    
    
        
        
        
    

那么就不用写dao的实现在service中就能掉用       mybatis默认会把mapper.xml映射为dao的实现

那么下面dao就能这样写：

package com.qbd.ssm.dao;
 
import java.util.List;
import java.util.Map;
 
import org.apache.ibatis.annotations.Delete;
 
import com.qbd.ssm.model.User;
 
public interface UserDao {
 
    public List getAll();
    public User getUser(User user);
    public int delete(User user);
    public int update(User user);
    public int add(User user);
    public List find(Map map);
    public Long getTotal(Map map);
}

service这样写

package com.qbd.ssm.service;
import java.util.List;
import java.util.Map;
import com.qbd.ssm.model.User; 
public interface UserService {
 
    public List getAll();
    public User getUser(User user);
    public int delete(User user);
    public int update(User user);
    public int add(User user);
    public List find(Map map);
    public Long getTotal(Map map);
}

service的实现：

package com.qbd.ssm.serviceimpl;
import java.util.List;
import java.util.Map;
import javax.annotation.Resource; 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.qbd.ssm.dao.UserDao;
import com.qbd.ssm.model.User;
import com.qbd.ssm.service.UserService;
 
@Service("userService")
public class UserServiceImpl implements UserService {
 
    private UserDao userDao;
    
    public UserDao getUserDao() {
        return userDao;
    }
 
    @Resource
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
 
    public List getAll() {
        // TODO Auto-generated method stub
        return userDao.getAll();
    }
 
    public User getUser(User user) {
        // TODO Auto-generated method stub
        return userDao.getUser(user);
    }
 
    public int delete(User user) {
        // TODO Auto-generated method stub
        return userDao.delete(user);
    }
 
    public int update(User user) {
        // TODO Auto-generated method stub
        return userDao.update(user);
    }
 
    public int add(User user) {
        // TODO Auto-generated method stub
        return userDao.add(user);
    }
 
    public List find(Map map) {
        // TODO Auto-generated method stub
        return userDao.find(map);
    }
 
    public Long getTotal(Map map) {
        // TODO Auto-generated method stub
        return userDao.getTotal(map);
    }
}

在这里面userDao不能写错，spring会按照name进行注入

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