報錯的原因是

 1 package com.chen.service.impl;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 
 6 import org.apache.catalina.User;
 7 import org.apache.ibatis.io.Resources;
 8 import org.apache.ibatis.session.SqlSession;
 9 import org.apache.ibatis.session.SqlSessionFactory;
10 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 
11 import org.springframework.context.ApplicationContext;
12 import org.springframework.context.support.ClassPathXmlApplicationContext;
13 
14 import com.chen.mapper.UserMapper;
15 import com.chen.service.UserService;
16 
17 public class UserServiceImpl implements UserService{
18 
19     
20     //聲明mapper變量
 

21     private UserMapper userMapper;//這行代碼如果要加private修飾的話，就不能放在下面的代碼中
22     public User userLoginService(String uname, String pwd) throws IOException {
23 
24         //獲取sqlsession對象
25 /*        InputStream is = Resources.getResourceAsStream("MyBatis.xml");
26         SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
 
27         SqlSession ss = factory.openSession();
28         //獲取Mapper接口實例化對象
29         UserMapper um=ss.getMapper(UserMapper.class);*/
30         //當我們在applicationcontext中配置好mybatis後，就不用再像上面一樣進行方法調用，獲取實例化對象
31         
32         //獲取spring容器對象
33 /*        ApplicationContext ac=new ClassPathXmlApplicationContext("applicationcontext.xml");
34         UserMapper um = (UserMapper) ac.getBean("userMapper");//mapper實例化接口的類名首字母小寫即是Bean id
35         已經在servlet獲取過一次spring容器對象了，所以我們沒必要再獲取一次
36         */
37         //操作數據庫
38         return (User) userMapper.selUser(uname, pwd);
39     }
40 
41 }

在java語法裏，方法的形參以及方法體中的變量都是局部變量，不能使用訪問權限修飾符public,private,protected。把Reader()方法裏的所有訪問權限修飾符private刪除或換成final就可以。

Illegal modifier for parameter userMapper; only final is permitted