web, XML

 
 
 SpringDispatcherServlet 
 Org. Springframework. Web. Servlet. DispatcherServlet 

 
 ContextConfigLocation 
 The classpath: com/Java/bean/for SpringMVC xml 
 

 1 & lt;/load - on - startup> 
 

 
 SpringDispatcherServlet 
/& lt;/url - pattern> 
 

 

for SpringMVC. XML

DAO layer

 @ Repository 
Public class BookDAOImpl implements BookDAO {

The @autowired 
private JdbcTemplate jdbcTemplate; 

@ Override 
The method of add delete 
} 

the service layer

 @ Service 
Public class BookServiceImpl implements BookService {

The @autowired 
Private BookDAO BookDAO; 

@ Override 
The method of add delete 

} 

JDBC + BookDAOImpl + BookServiceImpl Test normal, add and delete can use
But an error occurred when the Controller, the @autowired can't automatic injection
Controller

 @ Controller 
Public class bookController {

The @autowired 
Private BookDAO BookDAO; 

@ RequestMapping (value="https://bbs.csdn.net/page/book/list_book") 
Public String listBook Model (Model) {
List Booklist=bookDAO. Query (); 
Model. The addAttribute (" list ", booklist); 
Return "../manage/book_manage. JSP "; 
} 

} 

the index page

 & lt; A href="https://bbs.csdn.net/topics/list_book" & gt; The book management & lt;/a> 

book_manage page

 & lt; H1 & gt; List & lt;/h1 & gt; 
 
 Id 
 Name 
 

 
 ${list. Id} & lt;/td> 
 The ${list. The name} & lt;/td> 
 
 
 

Click on an error after the book management, error message:
Org. Apache. Jasper. JasperException: An exception occurred processing JSP page/page/manage/book_manage JSP at line 32

29:
30: & lt; C: forEach items="${list}" var="book" & gt;
31: & lt; Tr>
32: & lt; Td> ${list. Id} & lt;/td>
33: & lt; Td> The ${list. The name} & lt;/td>

Tried bookController class to remove traversal functions, can be normal jump
Try the output booklist, error Java. Lang. NullPointerException: always invoke a "com. Book. DAO. BookDAO. Query ()" because ". This BookDAO "is null