JSP test.

1. How to mix JSP and SSI # include?
In JSP, you can use the following method to include pure HTML:
<! -- # I nclude file = "data. Inc" -->
However, if data. inc contains JSP code, we can use:
<% @ Include file = "data. Inc" %>

2. How to execute a thread-safe JSP?
Add the following command:
<% @ Page isthreadsafe = "false" %>

3. How does JSP process data in HTML form?
You can use the built-in request object as follows:
<%
String item = request. getparameter ("item ");
Int howeter = new INTEGER (request. getparameter ("units"). intvalue ();
%>

4. How to include a static file in JSP?
Static include: <% @ include file = "copyright.html" %>
Dynamic inclusion: <JSP: Include page = "copyright.html" Flush = "true"/>

5. How to Use annotations in JSP?
There are four main methods:
1. <% -- And -- %>
2. //
3. /** And **/
4. <! -- And -->

6. How to perform browser redirection in JSP?
Use the following method: Response. sendredirect ("http://ybwen.home.chinaren.com/index.html ");
The HTTP header attribute can also be physically changed as follows:
<%
Response. setstatus (httpservletresponse. SC _moved_permanently );
String newlocn = "/newpath/index.html ";
Response. setheader ("location", newlocn );
%>

7. How to Prevent the output in JSP or servlet from being stored in the cache by browser?
Add the following script to the beginning of the JSP file:
<%
Response. setheader ("cache-control", "No-store"); /// HTTP 1.1
Response. setheader ("Pragma", "No-Cache"); // HTTP 1.0
Response. setdateheader ("expires", 0); // prevents caching at the Proxy Server
%>

8. How do I set cookies in JSP?
Cookie is sent as part of the HTTP header. You can set it as follows:
<%
Cookie mycookie = new cookie ("aname", "avalue ");
Response. addcookie (mycookie );
%>

9. How to delete a cookie in JSP?
<%
Cookie killmycookie = new cookie ("mycookie", null );
Killmycookie. setmaxage (0 );
Killmycookie. setpath ("/");
Response. addcookie (killmycookie );
%>

10. How to stop JSP execution during jsp request processing
For example:
<%
If (request. getparameter ("Wen ")! = NULL ){
// Do something
} Else {
Return;
}
%>

11. How to define methods in JSP
You can define methods, but you cannot directly access the built-in JSP objects, but pass through the parameter method. As follows:
<%!
Public String howbadfrom (httpservletrequest req ){
Httpsession ses = Req. getsession ();
...
Return Req. getremotehost ();
}
%>
<%
Out. Print ("in general, Lao Lee is not baddie ");
%>
<% = Howbadfrom (request) %>

12. If the browser has disabled cookies, how can I enable session in JSP to track them?
Use the URL to rewrite it, as shown below:
Hello1.jsp
<% @ Page session = "true" %>
<%
Integer num = new INTEGER (100 );
Session. putvalue ("num", num );
String url = response. encodeurl ("hello2.jsp ");
%>
<A href = "/<"; % = URL %> hello2.jsp </a>

Hello2.jsp
<% @ Page session = "true" %>
<%
Integer I = (integer) Session. getvalue ("num ");
Out. println ("Num value in session is" + I. intvalue ());
%>

13. Can I send an email in JSP?
You can use sun's dedicated package: sun.net. SMTP package. The following script uses the smtpclient class to send an email.
<% @ Page import = "sun.net. SMTP. smtpclient, java. Io. *" %>
<%
String from = "ybwen@sina.com ";
String to = "hewenjun@yeah.net, lei@who.com.cn ";
Try {
Smtpclient client = new smtpclient ("mail. XXXXX. XXX ");
Client. From (from );
Client. To ();
Printstream message = client. startmessage ();
Message. println ("to:" + );
Message. println ("Subject: sending email from JSP! ");
Message. println ("This was sent from a JSP page! ");
Message. println ();
Message. println ("cool! :-)");
Message. println ();
Message. println ("Good boy ");
Message. println ("Im in genius.com ");
Message. println ();
Client. closeserver ();
}
Catch (ioexception e ){
System. Out. println ("error sending email:" + E );
}
%>

14. Can I call a JSP error page in Servlet?
Of course there is no problem. The following shows how to call a JSP error page in a servlet control logic unit.
Protected void senderrorredirect (httpservletrequest request,
Httpservletresponse response, string errorpageurl,
Throwable E)
Throws servletexception, ioexception {
Request. setattribute ("javax. servlet. jsp. jspexception", e );
Getservletconfig (). getservletcontext ().
Getrequestdispatcher (errorpageurl). Forward (request,
Response );
}

Public void dopost (httpservletrequest request, httpservletresponse response ){
Try {
// Do something
} Catch (exception ex ){
Try {
Senderrorredirect (request, response, "/JSP/myerrorpage. jsp", ex );
} Catch (exception e ){
E. printstacktrace ();
}
}
}

15. How to communicate with JSP and Applet
How does JSP communicate with EJB sessionbean?
The following code snippet is a good example.
<% @ Page import = "javax. Naming. *, javax. RMI. portableremoteobject,
Foo. accounthome, foo. Account "%>
<%!
// Define a global reference to the sessionbeanhome interface instance
Accounthome acchome = NULL;

Public void jspinit (){
// Obtain the home interface instance
Initialcontext cntxt = new initialcontext ();
Object ref = cntxt. Lookup ("Java: COMP/ENV/EJB/accountejb ");
Acchome = (accounthome) portableremoteobject. Narrow (ref, accounthome. Class );
}
%>
<%
// Instantiate sessionbean
Account Acct = acchome. Create ();
// Call the Remote Method
Acct. dowhatever (...);
// So on
%>