Servlet & JSP – 13 – Listener
Merhaba Arkadaslar, Bu bolumde listener’lari inceleyecegiz. Bu listenerlar ;
javax.servlet.ServletContextListener public void contextInitialized(ServletContextEvent sce); public void contextDestroyed(ServletContextEvent sce);
javax.servlet.ServletContextAttributeListener public void attributeAdded(ServletContextAttributeEvent scae); public void attributeRemoved(ServletContextAttributeEvent scae); public void attributeReplaced(ServletContextAttributeEvent scae);
javax.servlet.ServletRequestListener public void requestDestroyed (ServletRequestEvent sre); public void requestInitialized (ServletRequestEvent sre);
javax.servlet.ServletRequestAttributeListener public void attributeAdded(ServletRequestAttributeEvent srae); public void attributeRemoved(ServletRequestAttributeEvent srae); public void attributeReplaced(ServletRequestAttributeEvent srae);
javax.servlet.http.HttpSessionListener public void sessionCreated(HttpSessionEvent se); public void sessionDestroyed(HttpSessionEvent se);
javax.servlet.http.HttpSessionAttributeListener public void attributeAdded(HttpSessionBindingEvent se); public void attributeRemoved(HttpSessionBindingEvent se); public void attributeReplaced(HttpSessionBindingEvent se);
javax.servlet.http.HttpSessionActivationListener public void sessionWillPassivate(HttpSessionEvent se); public void sessionDidActivate(HttpSessionEvent se);
javax.servlet.http.HttpSessionBindingListener public void valueBound(HttpSessionBindingEvent event); public void valueUnbound(HttpSessionBindingEvent event);
javax.servlet.ServletContextListener
ServletContextListener arabiriminde contextInitialized ve contextDestroyed metotlari bulunmaktadir. Bu metotlar javax.servlet.ServletContextEvent tipinde parametre alirlar.
Projemiz ayaga kaltiginda(deploy) contextInitialized metodu calisacaktir. Proje tekrar deploy olmadan once contextDestroyed metodu calisacaktir. (Ornegin ; bir Servlet uzerinde degisiklik yaptigimizda projemiz tekrar deploy olacaktir , bu durumda contextDestroyed metodunun calistigini gorebiliriz.)
Birden fazla ServletContextListener tanimlandiginda web.xml de tanimladigimiz sirada calisacaktir. Bu ozellik Servlet 3.0 ile gelmistir , oncesinde ise random sekilde calismaktadir.
_08_Listener.context
ServletContextListenerImpl.java
ServletContextListenerImpl2.java
ServletContextListenerImpl3.java
ServletContextListenerImpl.java
package _08_Listener.context;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class ServletContextListenerImpl implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("context initialized ...");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("context contextDestroyed ...");
}
}
ServletContextListenerImpl2.java
package _08_Listener.context;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class ServletContextListenerImpl2 implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("context initialized 2 ...");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("context contextDestroyed 2...");
}
}
ServletContextListenerImpl3.java
package _08_Listener.context;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class ServletContextListenerImpl3 implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("context initialized 3...");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("context contextDestroyed 3...");
}
}
listener tanimini web.xml ‘e eklerken etiketini kullaniriz;
<listener>
<listener-class>_08_Listener.context.ServletContextListenerImpl</listener-class>
</listener>
<listener>
<listener-class>_08_Listener.context.ServletContextListenerImpl2</listener-class>
</listener>
<listener>
<listener-class>_08_Listener.context.ServletContextListenerImpl3</listener-class>
</listener>
javax.servlet.ServletContextAttributeListener
ServletContextAttributeListener arabiriminde attributeAdded , attributeRemoved , attributeReplaced metotlari yer almaktadir.
Bu metotlar javax.servlet.ServletContextAttributeEvent tipinde parametre almaktadirlar. ServletContextAttributeEvent sinifi ServletContextEvent sinifini kalitmaktadir.
Bu metotlar Context attribute eklendiginde, silindiginde , ya de degistirildiginde/override edildiginde calisacaktir.
_08_Listener.context.attribute
ServletContextAttributeListenerImpl.java
SCAttributeListenMe.java
ServletContextAttributeListenerImpl.java
package _08_Listener.context.attribute;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
public class ServletContextAttributeListenerImpl implements ServletContextAttributeListener {
@Override
public void attributeAdded(ServletContextAttributeEvent scae) {
System.out.println("ServletContext attributeAdded : " + scae.getName() + " " + scae.getValue());
}
@Override
public void attributeRemoved(ServletContextAttributeEvent scae) {
System.out.println("ServletContext attributeRemoved : " + scae.getName() + " " + scae.getValue());
}
@Override
public void attributeReplaced(ServletContextAttributeEvent scae) {
System.out.println("ServletContext attributeReplaced : " + scae.getName() + " " + scae.getValue());
}
}
SCAttributeListenMe.java
package _08_Listener.context.attribute;
import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SCAttributeListenMe extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = getServletContext();
context.setAttribute("context attribute", "my context attribute");
context.setAttribute("context attribute", "my new context attribute");
context.removeAttribute("context attribute");
}
}
web.xml dosyamiza listener’i ve servlet’imizi ekleyelim ;
<listener>
<listener-class>_08_Listener.context.attribute.ServletContextAttributeListenerImpl</listener-class>
</listener>
<servlet>
<servlet-name>SCAttributeListenMe</servlet-name>
<servlet-class>_08_Listener.context.attribute.SCAttributeListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SCAttributeListenMe</servlet-name>
<url-pattern>/scattributelistenMe</url-pattern>
</servlet-mapping>
SCAttributeListenMe servlet’imizi calistirdigimizda context’e attribute ekledigimizde attributeAdded metodu calisacaktir. Daha sonrasinda bu attribute’u override ettigimizde attributeReplaced metodu calisir. Son olarak da bu attribute’u sildigimizde attributeRemoved metodu calisacaktir.
javax.servlet.ServletRequestListener
ServletRequestListener , requestInitialized ve requestDestroyed metotlarina sahiptir. |
Bu metotlar javax.servlet.ServletRequestEvent tipinde parametre almaktadir.
Web application’a bir istek/request geldiginde requestInitialized metodu calisacaktir. Bu istek sonlandiginda requestDestroyed metodu calisacaktir.
_08_Listener.request
ServletRequestListenerImpl.java
ServletRequestListenMe.java
ServletRequestListenerImpl.java
package _08_Listener.request;
import java.util.Date;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;
public class ServletRequestListenerImpl implements ServletRequestListener {
@Override
public void requestInitialized(ServletRequestEvent sre) {
System.out.println("requestInitialized...");
HttpServletRequest request = (HttpServletRequest) sre.getServletRequest();
String servletPath = request.getServletPath();
Date date = new Date();
System.out.println(servletPath + " " +date);
}
@Override
public void requestDestroyed(ServletRequestEvent sre) {
System.out.println("requestDestroyed...");
}
}
ServletRequestListenMe.java
package _08_Listener.request;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletRequestListenMe extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
System.out.println("Check Eclipse Console!");
}
}
web.xml dosyamiza listener ve servlet siniflarimizi ekleyelim;
<listener>
<listener-class>_08_Listener.request.ServletRequestListenerImpl</listener-class>
</listener>
<servlet>
<servlet-name>RequestListenMe</servlet-name>
<servlet-class>_08_Listener.request.ServletRequestListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RequestListenMe</servlet-name>
<url-pattern>/requestlistenme</url-pattern>
</servlet-mapping>
javax.servlet.ServletRequestAttributeListener
ServletRequestAttributeListener da ServletContextAttributeListener gibi calisir , benzer sekilde attributeAdded , attributeRemoved , attributeReplaced metotlarina sahiptir.
Bu metotlar ServletRequestAttributeEvent tipinde parameter almaktadir. ServletRequestAttributeEvent sinifi ServletRequestEvent sinifini kalitmaktadir.
_08_Listener.request.attribute
ServletRequestAttributeListenerImpl.java
ServletRequestAttributeListenMe.java
ServletRequestAttributeListenerImpl.java
package _08_Listener.request.attribute;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
public class ServletRequestAttributeListenerImpl implements ServletRequestAttributeListener {
@Override
public void attributeAdded(ServletRequestAttributeEvent srae) {
System.out.println("request attributeAdded :" + srae.getName() + " " + srae.getValue());
}
@Override
public void attributeRemoved(ServletRequestAttributeEvent srae) {
System.out.println("request attributeRemoved :" + srae.getName() + " " + srae.getValue());
}
@Override
public void attributeReplaced(ServletRequestAttributeEvent srae) {
System.out.println("request attributeReplaced :" + srae.getName() + " " + srae.getValue());
}
}
ServletRequestAttributeListenMe.java
package _08_Listener.request.attribute;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletRequestAttributeListenMe extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setAttribute("name", "myname attribute");
req.setAttribute("name", "new myname attribute");
req.removeAttribute("name");
}
}
web.xml dosyamiza listener ve servlet tanimimizi ekleyelim ;
<listener>
<listener-class>_08_Listener.request.attribute.ServletRequestAttributeListenerImpl</listener-class>
</listener>
<servlet>
<servlet-name>RequestAttributeListenMe</servlet-name>
<servlet-class>_08_Listener.request.attribute.ServletRequestAttributeListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RequestAttributeListenMe</servlet-name>
<url-pattern>/requestattributelistenme</url-pattern>
</servlet-mapping>
ServletRequestAttributeListenMe servlet’imizi calistirdigimizda once requestInitialized metodu calisir , daha sonrasinda attributeAdded metodu calisir. Request attribute override edildigi icin attributeReplaced metodu calisir , daha sonrasinda bu request attribute silindigi icin attributeRemoved metodu calisir. Son olarak da requestDestroyed metodu calisacaktir.
javax.servlet.http.HttpSessionListener
HttpSessionListener , sessionCreated ve sessionDestroyed metotlarina sahiptir. Bu metotlar yeni session olusturuldugunda ve bu session yok oldugunda calisacaktir.
Bu metotlar javax.servlet.http.HttpSessionEvent tipinde parametre almaktadir.
Yeni bir session olusturmak icin getSession metodu kullanilmaktadir.
_08_Listener.session
HttpSessionListenerImpl.java
HttpSessionListenMe.java
HttpSessionListenerImpl.java
package _08_Listener.session;
import java.util.Date;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class HttpSessionListenerImpl implements HttpSessionListener {
@Override
public void sessionCreated(HttpSessionEvent se) {
System.out.println("sessionCreated .... " + new Date());
}
@Override
public void sessionDestroyed(HttpSessionEvent se) {
System.out.println("sessionDestroyed ... " + new Date());
}
}
HttpSessionListenMe.java
package _08_Listener.session;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class HttpSessionListenMe extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
}
}
web.xml dosyamiza listener ve servlet tanimini ekleyelim;
<listener>
<listener-class>_08_Listener.session.HttpSessionListenerImpl</listener-class>
</listener>
<servlet>
<servlet-name>HttpSessionListenMe</servlet-name>
<servlet-class>_08_Listener.session.HttpSessionListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HttpSessionListenMe</servlet-name>
<url-pattern>/httpsessionlistenme</url-pattern>
</servlet-mapping>
HttpSessionListenMe servletimizi calistiralim eclipse console’u kontrol edelim.
javax.servlet.http.HttpSessionAttributeListener
HttpSessionAttributeListener da attributeAdded , attributeReplaced , attributeRemoved metotlarina sahiptir. Bu metotlarin javax.servlet.http.HttpSessionBindingEvent tipinde parametre alirlar.
_08_Listener.session.attribute
HttpSessionAttributeListenerImpl.java
HttpSessionAttributeListenMe.java
HttpSessionAttributeListenerImpl.java
package _08_Listener.session.attribute;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
public class HttpSessionAttributeListenerImpl implements HttpSessionAttributeListener {
@Override
public void attributeAdded(HttpSessionBindingEvent se) {
System.out.println("attributeAdded : " + se.getName() + " " + se.getValue());
}
@Override
public void attributeRemoved(HttpSessionBindingEvent se) {
System.out.println("attributeRemoved : " + se.getName() + " " + se.getValue());
}
@Override
public void attributeReplaced(HttpSessionBindingEvent se) {
System.out.println("attributeReplaced : " + se.getName() + " " + se.getValue());
}
}
HttpSessionAttributeListenMe.java
package _08_Listener.session.attribute;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class HttpSessionAttributeListenMe extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
session.setAttribute("session attribute", "my attribute");
session.setAttribute("session attribute", "my new attribute");
session.removeAttribute("session attribute");
}
}
web.xml dosyamiza listener ve servlet’imizi ekleyelim;
<servlet>
<servlet-name>HttpSessionAttributeListenMe</servlet-name>
<servlet-class>_08_Listener.session.attribute.HttpSessionAttributeListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HttpSessionAttributeListenMe</servlet-name>
<url-pattern>/httpsessionattributelistenme</url-pattern>
</servlet-mapping>
HttpSessionAttributeListenMe sinifimizi calistirdigimizda Eclipse Console’da ciktilari inceleyebiliriz.
javax.servlet.http.HttpSessionBindingListener
HttpSessionBindingListener , valueBound ve valueUnbound metotlarina sahiptir. Bu metotlar javax.servlet.http.HttpSessionBindingEvent tipinde parametre almaktadir.
_08_Listener.session.binding
HttpSessionBindingListenerImpl.java
HttpSessionBindingListenMe.java
Session’a HttpSessionBindingListener tipinde bir attribute eklendiginde valueBound metodu , HttpSessionBindingListener tipinde attribute sessiondan silindiginde valueUnbound metodu calisacaktir.
HttpSessionBindingListenerImpl.java
package _08_Listener.session.binding;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
public class HttpSessionBindingListenerImpl implements HttpSessionBindingListener {
@Override
public void valueBound(HttpSessionBindingEvent event) {
System.out.println("valueBound HttpSessionBindingListenerImpl... ");
}
@Override
public void valueUnbound(HttpSessionBindingEvent event) {
System.out.println("valueUnbound HttpSessionBindingListenerImpl... ");
}
}
HttpSessionBindingListenMe.java
package _08_Listener.session.binding;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class HttpSessionBindingListenMe extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
HttpSessionBindingListenerImpl attribute = new HttpSessionBindingListenerImpl();
session.setAttribute("binding attribute", attribute);
session.removeAttribute("binding attribute");
}
}
session attribute olarak HttpSessionBindingListenerImpl objesini(HttpSessionBindingListenerImpl IS-A HttpSessionBindingListener ) ekledik. Bu nedenle valueBound metodu calisacaktir.
removeAttribute ile ilgili attribute silindigin icin valueUnbound metodu calisacaktir.
HttpSessionBindingListener’i web.xml e eklememize gerek yoktur! Sadece servlet’imizi eklememiz yeterli olacaktir.
<!--HttpSessionBindingListener i listener olarak eklemeye gerek yoktur.
Dilersek yazabiliriz. -->
<listener>
<listener-class>_08_Listener.session.binding.HttpSessionBindingListenerImpl</listener-class>
</listener>
<servlet>
<servlet-name>HttpSessionBindingListenMe</servlet-name>
<servlet-class>_08_Listener.session.binding.HttpSessionBindingListenMe</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HttpSessionBindingListenMe</servlet-name>
<url-pattern>/httpsessionbindinglistenme</url-pattern>
</servlet-mapping>
javax.servlet.http.HttpSessionActivationListener
HttpSessionActivationListener , sessionWillPassivate ve sessionDidActivate metotlarina sahiptir. Bu metotlar javax.servlet.http.HttpSessionEvent tipinde parametre alirlar.
Uygulamamizin dagitik/distributed bir sekilde calistigini dusunelim. Her serverda farkli JVM olacaktir. Her JVM icin bir ServletContext objesi ve yine her JVM deki Servletlere karsilik ServletConfig objesi olacaktir. Sadece HttpSession objesi bir tane olacaktir ! Yani ayni session objesinin kopyasi farkli JVM’lerde olamaz! Bununla birlikte bu HttpSession objesi bir JVMden diger JVM yani bir dagitik sistemden diger dagitik sisteme gecebilir.
HttpSessionActivationListener arabirimindeki metotlar bu HttpSession objesini farkli JVMler arasinda gecisi/tasinmasi sonrasinda calisacaktir.
package _08_Listener.session.activation;
import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionEvent;
public class HttpSessionActivationListenerImpl implements HttpSessionActivationListener {
@Override
public void sessionWillPassivate(HttpSessionEvent se) {
System.out.println("sessionWillPassivate ...");
}
@Override
public void sessionDidActivate(HttpSessionEvent se) {
System.out.println("sessionDidActivate ...");
}
}
web.xml dosyamiza listener’i ekleyelim ;
<listener>
<listener-class>_08_Listener.session.activation.HttpSessionActivationListenerImpl</listener-class>
</listener>
Yazimi burada sonlandiriyorum.
Herkese Bol Javali Gunler dilerim.
Be an oracle man , import java.*;
Levent Erguder
OCP, Java SE 6 Programmer
OCE, Java EE 6, Web Component Developer
