JSP Listener Listener (ii)

Servletcontextattributelistener

It is used to monitor the change of ServletContext , which is the application range, and implements this structure to rewrite three methods

• Attributeadded () method: automatically called when adding parameters to the application
• Attributeremoved () method: Called when the parameter in the application is removed
• Attributereplaced () method: Called when modifying a parameter in application

1  PackageCom.huayu.listener;2 3 Importjavax.servlet.ServletContextAttributeEvent;4 ImportJavax.servlet.ServletContextAttributeListener;5 ImportJavax.servlet.annotation.WebListener;6 @WebListener7  Public classListener3Implementsservletcontextattributelistener{8     9 @OverrideTen      Public voidattributeadded (Servletcontextattributeevent event) { OneString named=event.getname (). toString (); AString value=Event.getvalue (). toString (); -SYSTEM.OUT.PRINTLN ("Application" adds a "+named+" variable value of "+value); -          the     } -  - @Override -      Public voidattributeremoved (Servletcontextattributeevent event) { +String named=event.getname (). toString (); -String value=Event.getvalue (). toString (); +SYSTEM.OUT.PRINTLN ("Application" Removes a "+named+" variable with a value of "+value); A          at          -          -     } -  - @Override -      Public voidattributereplaced (Servletcontextattributeevent event) { inString named=event.getname (). toString (); -String value=Event.getvalue (). toString (); toSystem.out.println ("+named+" Variable value in "Application" changes to "+value); +     } -  the}

Servletrequestlistener

The request to listen to the user arrives, the end of the request

Requestinitialized: The method is triggered when a user request arrives and is initialized

Requestdestroyed: End of user request, triggered when the method is destroyed

Servletrequestattributelistener

Used to listen for changes in the request scope variables

Attributeadded ()

Attributereplaced ()

Attributeremoved ()

1  PackageCom.huayu.listener;2 3 Importjavax.servlet.ServletRequest;4 Importjavax.servlet.ServletRequestAttributeEvent;5 ImportJavax.servlet.ServletRequestAttributeListener;6 Importjavax.servlet.ServletRequestEvent;7 ImportJavax.servlet.ServletRequestListener;8 ImportJavax.servlet.annotation.WebListener;9 Importjavax.servlet.http.HttpServletRequest;Ten @WebListener One  Public classListener4Implementsservletrequestlistener,servletrequestattributelistener{ A  - @Override -      Public voidrequestdestroyed (servletrequestevent arg0) { the  -HttpServletRequest request=(HttpServletRequest) arg0.getservletrequest (); -SYSTEM.OUT.PRINTLN ("---Sent to" +request.getrequesturi () + "Request destroyed-----"); -          +     } -  + @Override A      Public voidrequestinitialized (servletrequestevent arg0) { atHttpServletRequest request=(HttpServletRequest) arg0.getservletrequest (); -SYSTEM.OUT.PRINTLN ("---Sent to" +request.getrequesturi () + "Request initialized-----"); -     } -  - @Override -      Public voidattributeadded (servletrequestattributeevent arg0) { inServletRequest request=arg0.getservletrequest (); -String name=arg0.getname (); toString value=Arg0.getvalue (). toString (); +A property named "+name+" with a value of "+value+" has been added to the System.out.println (request+ "Scope"); -          the     } *  $ @OverridePanax Notoginseng      Public voidattributeremoved (servletrequestattributeevent arg0) { -ServletRequest request=arg0.getservletrequest (); theString name=arg0.getname (); +String value=Arg0.getvalue (). toString (); AA property named "+name+" with a value of "+value+" has been added to the System.out.println (request+ "Scope")); the          +     } -  $ @Override $      Public voidattributereplaced (servletrequestattributeevent arg0) { -ServletRequest request=arg0.getservletrequest (); -String name=arg0.getname (); theString value=Arg0.getvalue (). toString (); -A property named "+name+" with a value of "+value+" has been added to the System.out.println (request+ "scope) and replaced by");Wuyi          the     } -  Wu}

Httpsessionlistener

For monitoring user session creation and destruction

sessioncreated (httpsessionevent se): When session

Called when it is built.

sessiondestroyed (httpsessionevent se)

executes when no client links to the session

Httpsessionattributelistener

Using the same method as above

JSP Listener Listener (ii)