JSP question and answer set (to the first contact JSP)

How is JS mixed with JSP and SSI #include?
You can include pure HTML in a JSP in the following ways:
<!--#include file= "Data.inc"-->
But if the data.inc contains JSP CODE, we can use:
<% @include file= "Data.inc"%>
How do I perform a thread-safe JSP?
Just add the following instructions <br>
<%@ page isthreadsafe= "false"%>
How does a JSP handle the data in an HTML form?
Through the inside of the request object can be as follows:
<%<br>
String item = request.getparameter ("item");
int howmany = new Integer (Request.getparameter ("units")). Intvalue ();
%>
How does a JSP contain a meditation file?
The meditation includes the following: <%@ include file= "copyright.html"%>
The motion includes the following: <jsp:include page= "copyright.html" flush= "true"/>
How to use annotations in JSP?
There are four main methods:
1. <%--and--%>
2. //
3. /** and **/
4. <!--and-->
How do I perform a browse redirect in a JSP?
Use the following way: Response.sendredirect ("http://ybwen.home.chinaren.com/index.html";);
You can also change the HTTP header physically, as follows:
<%
Response.setstatus (httpservletresponse.sc_moved_permanently);
String newlocn= "/newpath/index.html";
Response.setheader ("Location", NEWLOCN);
%>
How do I prevent the output in the JSP or servlet from being saved in the cache by browser?
Add the following toe to the beginning of the JSP file:
<%
Response.setheader ("Cache-control", "No-store"); File://HTTP 1.1
Response.setheader ("Pragma", "No-cache"); File://HTTP 1.0
Response.setdateheader ("Expires", 0); File://prevents caching at the proxy server
%>
How do I set cookies in a JSP?
Cookies are made? A portion of the HTTP header is sent, and the following methods can be set:
<%
Cookie MyCookie = new Cookie ("Aname", "avalue");
Response.addcookie (MyCookie);
%>
How do I delete a cookie in the JSP?
<%
Cookie Killmycookie = new Cookie ("MyCookie", null);
Killmycookie.setmaxage (0);
Killmycookie.setpath ("/");
Response.addcookie (Killmycookie);
%>
How do I stop the JSP in the request of a JSP?
The following example:
<%
if (Request.getparameter ("Wen")!= null) {
Do something
} else {
Return
}
%>
How do I define a method in a JSP?
You can define the method, but you can't access the JSP's internal object directly, but pass the parameters through the method. As follows:
<%!
Public String Howbadfrom (HttpServletRequest req) {
HttpSession ses = req.getsession ();
...
return Req.getremotehost ();
}
%>
<%
Out.print ("In General,lao Lee are not baddie");
%>
<%= Howbadfrom (Request)%>

If browser has closed cookies, how do I open the session in JSP?
You can use the URL rewrite as follows:
hello1.jsp
<%@ page session= "true"%>
<%
Integer num = new integer (100);
Session.putvalue ("num", num);
String URL =response.encodeurl ("hello2.jsp");
%>
Hello2.jsp</a>
hello2.jsp
<%@ page session= "true"%>
<%
Integer i= (integer) session.getvalue ("num");
Out.println ("Num value in the session is" +i.intvalue ());
%>

Can I send email in JSP?
You can use Sun's dedicated package: SUN.NET.SMTP package. The following script uses SmtpClient to send 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 (to);
PrintStream message = Client.startmessage ();
Message.println ("to:" + to);
MESSAGE.PRINTLN ("subject:sending email from jsp!");
Message.println ("This is sent from a JSP page!");
Message.println ();
Message.println ("cool!:-)");
Message.println ();
Message.println ("Good Boy");
Message.println ("I ' m in Genius.com");
Message.println ();
Client.closeserver ();
}
catch (IOException e) {
System.out.println ("ERROR Sending EMAIL:" +e);
}
%>

Can I adjust a JSP error page in the servlet?
Of course, the following shows how to adjust 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 ();
}
}
}
How does JSP interact with EJB Sessionbean?
The following code section is a good example.
<%@ page import= "javax.naming.*, Javax.rmi.PortableRemoteObject,
Foo. Accounthome, Foo. Account "%>
<%!
FILE://defines a global reference to the Sessionbeanhome interface example
Accounthome Acchome=null;
public void Jspinit () {
file://Get Home Interface case
InitialContext cntxt = new InitialContext ();
Object ref= cntxt.lookup ("JAVA:COMP/ENV/EJB/ACCOUNTEJB");
Acchome = (accounthome) portableremoteobject.narrow (Ref,accounthome.class);
}
%>
<%
file://in the actual case of Sessionbean
Account acct = Acchome.create ();
file://method for remote-end tuning
Acct.dowhatever (...);
Mailroom
%>