Listen to SevletContext creation and listen to the process of saving a Sesison to a file (57), context

Listen to SevletContext creation and listen to the process of saving a Sesison to a file (57), context

Other listeners

Listener	Listener	Event object monitored
HttpSessionActivationListener	HttpSession-Listen for HttpSession activation and pause.	HttpSessionEvent
HttpSessionAttributeListener	HttpSession-listens for changes in the attributes of a session. S. setAttributee ();	HttpSessionBindingEvent
HttpSessionBindingListener	HttpSession-which object to listen to is bound to the session. S. setAtrri (name, User );
HttpSessionListener	HttpSesion-listening for sessioin creation and destruction	HttpSessionEvent
ServletContextAttributeListener	ServletContext-attributes changed
ServletContextListener[W1]	ServletContext creation and destruction
ServletRequestListener-SerlvetRequestAttibuteListner	Rrequest-create and destroy Request attribute change

1 ServletContextListener is used to listen for SevletContext Creation

All listeners on the web are global-all are directly created by tomcat when the project is started.

The listener has no order. Only the listening objects are different.

Multiple listeners can exist in a project.

PackageCn. hx. listener;

ImportJava. io. BufferedReader;

ImportJava. io. File;

ImportJava. io. FileNotFoundException;

ImportJava. io. FileReader;

ImportJava. io. PrintWriter;

ImportJava.net. URL;

ImportJavax. servlet. ServletContextEvent;

ImportJavax. servlet. ServletContextListener;

Public ClassMyContextListenerImplementsServletContextListener {

// Read the data stored before the database at startup

Public VoidContextInitialized (ServletContextEvent SC ){

System.Err. Println ("application created:" + SC. getServletContext ());

URL url = MyContextListener.Class. GetClassLoader (). getResource ("count.txt ");

String path = url. getFile ();

System.Err. Println (path );

Try{

BufferedReader bf =NewBufferedReader (NewFileReader (path ));

String line = bf. readLine ();

Integer count = Integer.ValueOf(Line );

SC. getServletContext (). setAttribute ("count", count );

System.Err. Println ("Initial Value:" + count );

}Catch(Exception e ){

E. printStackTrace ();

}

 

}

// Save some data to the database or file when this object is destroyed

Public VoidContextDestroyed (ServletContextEvent e ){

System.Err. Println ("destroyed:" + e. getServletContext ());

// Save it to the file

URL url = MyContextListener.Class. GetClassLoader (). getResource ("count.txt ");

String path = url. getFile ();

System.Err. Println (path );

File file =NewFile (path );

Try{

PrintWriter out =NewPrintWriter (file );

// Obtain applicat data

Integer count = (Integer) e. getServletContext (). getAttribute ("count ");

Out. print (count );

Out. close ();

}Catch(FileNotFoundException e1 ){

E1.printStackTrace ();

}

}

}

Load all configuration files at one time when the project starts.

2. Listen to the process of saving a Sesison to a file.

Step 1: Write Bean implementationHttpSessionActivationListener

PackageCn. hx. domain;

ImportJava. io. Serializable;

ImportJavax. servlet. http. HttpSessionActivationListener;

ImportJavax. servlet. http. HttpSessionEvent;

Public ClassPersonImplementsSerializable, HttpSessionActivationListener {

PrivateString name;

PublicPerson (){

}

PublicPerson (String name ){

This. Name = name;

}

PublicString getName (){

ReturnName;

}

Public VoidSetName (String name ){

This. Name = name;

}

Public VoidSessionWillPassivate (HttpSessionEvent se ){

System.Err. Println ("saved to file..." +This. GetName ());

}

Public VoidSessionDidActivate (HttpSessionEvent se ){

System.Err. Println ("activated from the file..." +This. GetName ());

}

@ Override

PublicString toString (){

Return"Person [name =" + name + "]";

}

}

Step 2: configure this project

<Context docBase = "D :\\ programfiles \ MyEclipse10 \ wk3 \ WebRoot">

<Manager className = "org. apache. catalina. session. PersistentManager"

SaveOnRestart = "true">

<Store className = "org. apache. catalina. session. FileStore"

Directory = "d:/a">

</Store>

</Manager>

</Context>

Step 3: Test

<%

If(Session. getAttribute ("p") =Null){

IntA =NewRandom (). nextInt (100 );

Person p =NewPerson ("" + );

Session. setAttribute ("p", p );

}

// Save the cookie

Cookie c =NewCookie ("JSESSIONID", session. getId ());

C. setMaxAge (60*30 );

C. setPath (request. getContextPath ());

Response. addCookie (c );

%>

<Hr/>

$ {P}

<Hr/>

<% = Session. getId () %>