"Head first Servlets and JSP" Note 24:include instructions and include Actions & param actions & foward actions

Last Update:2017-06-22 Source: Internet

Author: User

Tags autoload

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Include directives and include actions

1. Sample Code

<%@ PageContentType= "Text/html;charset=utf-8"language= "Java" %><%@ PageImport= "java.io.*,java.util.*" %><HTML><Head>  <title>Auto Refresh Header Example</title></Head><Body><%--Insert the header file here--%> <%@ include  file= "header.jsp"%> <center>  <jsp:include  page= "footer.jsp" /> </Body></HTML>

 <  %@ page  contenttype  = "Text/html;charset=utf-8"   language  = "Java"  %  >  <  img  src  = "Images/header.jpg"   Alt  = "Shanghai Flower Harbor-Tulip"  />  <  p  >  I am header </ p  >

<contentType= "Text/html;charset=utf-8"  language= "java"  %><src= "images/header.jpg"  alt = "Shanghai Flower Harbor-Tulip" /> < P > I am the header </p>

2. Source Code Analysis

Web Project Structure

Package these files into a war, deploy to the local Tomcat WebApps, and start Tomcat.

After the first access to index.jsp, the following files are generated

We observed that there was no header_jsp generated, as we could imagine, because we used the include directive instead of the include action.

Then see index_jsp Source code:

Try {  response.setcontenttype ( "Text/html;charset=utf-8");      PageContext = _jspxfactory.getpagecontext (this, request, response, NULL, True, 8192, true);      _jspx_page_context = PageContext;      application = Pagecontext.getservletcontext ();      Config = Pagecontext.getservletconfig ();      Session = Pagecontext.getsession ();      out = Pagecontext.getout (); _jspx_out =Out  ; Out.write ( "\ n");      Out.write ("\ n");      Out.write ("\ n");      Out.write ("); out.write ("\r\n"); Out.write ("<p> I am header </p>\r\n"); Out.write ("\ r \ n");      Out.write ("\ n");      Out.write ("\ n");      Out.write ("<center>\n");      Out.write ("//Set refresh, AutoLoad time as 5 seconds Response.setintheader ("Refresh", 60);    Get current time Calendar calendar = new GregorianCalendar ();    String am_pm;    int hour = Calendar.get (Calendar.hour);    int minute = Calendar.get (Calendar.minute);    int second = Calendar.get (Calendar.second);    if (Calendar.get (calendar.am_pm) = = 0) am_pm = "AM";    else am_pm = "PM";    String CT = hour+ ":" + Minute + ":" + second + "+ am_pm;        Out.println ("Crrent time:" + CT + "\ n");      Out.write ("\ n");      Out.write ("</center>\n");      Out.write ("\ n"); Out.write (' \ n '); org.apache.jasper.runtime.JspRuntimeLibrary.include (Request, response,       "footer.jsp", out, false ); Out.write ( "\ n");      Out.write ("\ n");      Out.write ("</body>\n");    Out.write ("

The bold distinction is the conversion code for the include directive and the include action.

Param action

Modify the index.jsp code above:

<%--Insert Footer file here--%><jsp:include page= "footer.jsp" >  <jsp:param name= "SubTitle" value= "We take the String out of SOAP. "/></jsp:include>

Modify Footer.jsp

<%@ page contenttype= "Text/html;charset=utf-8" language= "java"%><a href= "index.jsp" >home page I'm the footer! </a>
Effect
Foward Action
Garbled problem is not resolved, can only input Chinese.
<%@ page contenttype= "Text/html;charset=utf-8" language= "java"%>   <(Request.getparameter ("UserName")null) {%  >        <page= "handleit.jsp"/>    <%}% >      <p> Hello! ${param.username}</p></body>
handleit.jsp
<%@ PageContentType= "Text/html;charset=utf-8"language= "Java" %><HTML><Body>    <% request.setcharacterencoding("Utf-8"); %>    <P>I'm sorry, but you need to log in again.</P>    <formAction= "hello.jsp">        <P>User name:<inputtype= "text"name= "UserName"></P>        <P><inputtype= "Submit"></P>    </form></Body></HTML>
"Head first Servlets and JSP" Note 24:include instructions and include Actions & param actions & foward actions

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