8. listener
============================================== ===
two methods register a listener:
1. @ WebListener annotation
@WebListener
public class {} ListenerClass the implements listenerInterface
2.web.xml using a listener element.
<listener>
<listener-class> Fully-qualified listener class </ listener-class>
</ listener>
the Servlet the Context Listener - implements the interface of ServletContextListener
1.ServletContextListener: initialization and deconstruction of ServletContext respond.
void contextInitialized (ServletContextEvent event); --- > The method of rewriting main
void the contextDestroyed (ServletContextEvent Event);
2.ServletContextAttributeListener:
void attributeAdded (ServletContextAttributeEvent SCAE);
attributeRemoved void (ServletContextAttributeEvent SCAE);
void attributeReplaced (ServletContextAttributeEvent SCAE);
the Session Listener - Interface implement the HttpSessionListener
1.HttpSessionListener
2.HttpSessionActivationListener
3.HttpSessionAttributeListener
4.HttpSessionBindingListender
user counter instance
ServletRequest listener - implement interface ServletRequestListener
1.ServletRequestListener
2. ServletRequestAttributeListener
3.AsyncListener
user access time
9. The filter
======================================= ==========
filter means intercepts the request, and passed to the requested resource for a ServletResponse ServletRequest or object.
Filter API
include: Filter, FilterConfig and FilterChain.
Javax.servlet.Filter filter must implement the interface. 3 method:
<filter-name>
void the init (the FilterConfig FilterConfig);
void the doFilter (the ServletRequest REQ, the ServletResponse RESP, the FilterChain FC);
void Destory ()
method FilterConfig interface:
public String getFilterName ();
public the ServletContext GetServletContext ();
public String the getInitParameter (String name);
public the Enumeration <String> the getInitParameterNames () ;
method FilterChain interface:
public void the doFilter (the ServletRequest Request, the ServletResponse Response);
configuring filters method:
1. @ WebFilter annotation
2.web.xml used filter element and the filter-mapping
<filter>
<filter-name> XXX < / filter-name>
<filter-class> yyy </ filter-class>
</ filter>
<filter-Mapping>
<URL-pattern> / * </ URL-pattern>
</ filter-mapping>
Example 1: Log filter
Example 2: Images protection filter
Example 3: Download count filter
order filters: web.xml in order to write the call.
10. The application design
configuration JNDI Datasource steps:
1. Copy the JDBC driver mysql-connector-java-5.1.44- bin.jar to the tomcat / lib / directory.
2.Context configuration: the META-INF / context.xml
<the Context>
<the Resource name = "JDBC / the TestDB" the auth = "Container" type = "the javax.sql.DataSource"
maxTotal = "100" maxIdle = "30" = maxWaitMillis "10000"
username = "the root" password = "the root" driverClassName = "com.mysql.jdbc.Driver"
URL = "JDBC: MySQL: //192.168.15.45: 3307 / a_spider_test" />
</ the Context>
3.Web .xml configuration: the WEB-INF / the web.xml
<Resource-REF>
<
<res-auth>Container</res-auth>
</resource-ref>
4.编写代码：
Context context = new InitialContext();
DataSource dataSource = (DataSource) context.lookup("java:comp/env/jdbc/TestDB");
Connection con = dataSource.getConnection();