Details of how servlets are used

The life cycle approach of the servlet:

Init () Destroy () doget (httpservletrequest request,httpservletresponse response) client requests are encapsulated in the request, The server response is encapsulated in the response
-------------------------------------------------------------------------------configuration of Web. XML (multiple servlets configured with multiple Servlets and servlet-mapping tags)

<servlet>  <Servlet-name>Servelettest1</Servlet-name>       <Servlet-class>Com.web.servlet.Servelettest1</Servlet-class>//full path</servlet>  <servlet-mapping>                                                                    <Servlet-name>Servelettest1</Servlet-name>  <Url-pattern>/servelettest1</Url-pattern>//Browse request alias, preceded by Slash</servlet-mapping>

 Public void throws ioexception{               = Response.getwriter ();                              // This output stream is from the Web server to the browser, printed on the Web server        Pw.print ("Hello World");        Pw.close ();    }      Public void throws ioexception{        = response.getwriter ();        Pw.print ("Hello World");        Pw.close ();    }

In the index.jsp

<a href= "./servelettest1" >hello world<a><form action= "Servelettest1" method= "POST" >     //  Servelettest1 is <url-pattern>/Servelettest1</url-pattern><input type= "Submit" value= " Submit ">

Http://localhost:8088/Servelettest1//servelettest1 is <url-pattern>/servelettest1</url-pattern>http://localhost:8088/ index.jsp-----------------------------------------------------------------------------------using Request and responseresponse.ge Twriter ();             Get the client parameter method Request.getparameter ("username"); Get the parameter index.jsp corresponding code snippet for <a href= "Servelettest1?username=boyce" >hello world<a> The Servlet accepts the request encapsulation information:

 Public void throws ioexception{        = Request.getparameter ("username");                                          // Get user name        String Password = request.getparameter ("password");         = Response.getwriter ();        Pw.print ("Hello World" +username+password);        Pw.close ();    }

Corresponding JSP:

<form action= "Servelettest1" method= "POST" >              User account:<input type= "text" name= "username" >  User password:<input type= "password" name= "password" ><input type= "Submit" value= "Submit" ></form>

----------------------------------------------------------- Server.xml: Chinese garbled from client to server<connector port= "8080" protocol= "http/1.1" connectiontimeout= "20000"uriencoding= "Utf-8"redirectport= "8443"/> encountered Server.xml denied access solution: Go in and select Edit, and then select the user permission check Full Control can// Chinese garbled response.setcharacterencoding from server to client ("Utf-8"); Response.setcontenttype (Text/html;charset=utf-8) The servlet implements the page jump:

 PackageCom.web.servlet;Importjava.io.IOException;ImportJavax.servlet.http.HttpServlet;Importjavax.servlet.http.HttpServletRequest;ImportJavax.servlet.http.HttpServletResponse; Public classServelettest2extendshttpservlet{ Public voidinit () {} Public voiddestroy () {} Public voidDoPost (httpservletrequest request,httpservletresponse response)throwsioexception{String uname= Request.getparameter ("username"); String Password= Request.getparameter ("Password"); System.out.println ("Servelet2 is called"); //page JumpResponse.sendredirect ("Servelettest3");//implement a page jump    }}

Method Two:

RequestDispatcher rd = Request.getrequestdispatcher ("Servelettest3"); Rd.forward (request,response);

INDEX.JSP:

<form action= "Servelettest2" method= "POST" >              User account:<input type= "text" name= "username" >  User password:<input type= "password" name= "password" ><input type= "Submit" value= "Submit" ></form>

dopost Chinese garbled solution:

 Public voidDoPost (httpservletrequest request,httpservletresponse response)throwsioexception{request.setcharacterencoding ("UTF-8");//troubleshoot the request server Chinese charactersResponse.setcharacterencoding ("UTF-8");//troubleshoot server-to-client garbled issuesResponse.setcontenttype ("text/html; Charset=utf-8 ");//troubleshoot server-to-client garbled issuesString username = request.getparameter ("username"); String Password= Request.getparameter ("Password"); PrintWriter PW=Response.getwriter (); Pw.print ("Hello World" +username+password); SYSTEM.OUT.PRINTLN (username+password);    Pw.close (); }

Filter:

<filter>  <filter-name>/filter1</filter-name>  <filter-class> com.web.servlet.characterfilter</filter-class>  </filter>  <filter-mapping>  <filter-name>/filter1</filter-name>  <url-pattern>/*</ Url-pattern>                                                       //asterisk means that all transmissions go through it  </filter-mapping>

 PackageCom.web.servlet;Importjava.io.IOException;ImportJavax.servlet.Filter;ImportJavax.servlet.FilterChain;ImportJavax.servlet.FilterConfig;Importjavax.servlet.ServletException;Importjavax.servlet.ServletRequest;ImportJavax.servlet.ServletResponse; Public classCharacterfilterImplementsfilter{@Override Public voiddestroy () {//TODO auto-generated Method Stub} @Override Public voidDoFilter (ServletRequest arg0, Servletresponse arg1, Filterchain arg2)throwsIOException, servletexception {//TODO auto-generated Method StubArg0.setcharacterencoding ("Utf-8"); Arg1.setcharacterencoding ("Utf-8"); Arg1.setcontenttype ("Text/html; Charset=utf-8 ");    Arg2.dofilter (arg0, arg1); } @Override Public voidInit (Filterconfig arg0)throwsservletexception {//TODO auto-generated Method Stub    }}

Listener: The servlet defines a variety of class listeners that are primarily used to listen on the three domain objects of servletcontext,httpsession and ServletRequest:   Httpsessionlistener interface for monitoring the creation and destruction of HttpSession   (1) When a session is created, the sessioncreated (httpsessionevent se) method is called. (2) When a session is destroyed, the Sessiondestroy (httpsessionevent se) method is called. session domain object creation and destruction timing created: Yoghurt when first accessed, the server creates a session destroy: If the user 30 minutes will be used, the server will be destroyed session, we can also in Web. XML The session Expiration time

<session-config>  <session-timeout>1</session-timeout>            // Set the listening time to one minute, If not modified, default is 30 minutes </session-config>

 PackageCom.web.servlet;ImportJavax.servlet.http.HttpSessionAttributeListener;Importjavax.servlet.http.HttpSessionBindingEvent;Importjavax.servlet.http.HttpSessionEvent;ImportJavax.servlet.http.HttpSessionListener;//Implement Interface Httpsessionlistener Public classOnlinecounterlistenerImplementshttpsessionlistener,httpsessionattributelistener{Private intCount=0; @Override Public voidsessioncreated (httpsessionevent arg0) {//TODO auto-generated Method Stubcount++; System.out.println ("There is a new user access, the current number of visitors is:" +count); } @Override Public voidsessiondestroyed (httpsessionevent arg0) {//TODO auto-generated Method Stubcount--; System.out.println ("There is an exit, the current number is:" +count); } @Override Public voidattributeadded (httpsessionbindingevent arg0) {//TODO auto-generated Method Stub} @Override Public voidattributeremoved (httpsessionbindingevent arg0) {//TODO auto-generated Method Stub} @Override Public voidattributereplaced (httpsessionbindingevent arg0) {//TODO auto-generated Method Stub    }}

Summary: Servlet step 1. Create a servlet Class (inherited from HttpServlet) 2. Three methods: public void init () {} public void Destroy () {} public void DoPost (HttpServletRequest request, httpservletresponse response) {}3. Gets the value in the JSP by GetParameter string username = Request. GetParameter ("username"); 4. Then call the JDBC or Hibernate class (Dao) to add or delete the object 5. Jump page//forward to the Registration results page Request.getrequestdispatcher ("result.jsp"). Forward (request, response);

Details of how servlets are used