JSP中可能会碰到的问题解答

 
HttpSession ses = req.getSession();
...
return req.getRemoteHost();
}
% &gt
&lt %
out.print("in general,lao lee is not baddie ");
% &gt
&lt %= howBadFrom(request) % &gt </P>

12、假如BROWSER已关闭了COOKIES，在JSP中我如何打开SESSION来跟踪
使用URL重写即可，如下：
hello1.jsp
&lt %@ page session="true" % &gt
&lt %
Integer num = new Integer(100);
session.putvalue("num",num);
String url =response.encodeURL("hello2.jsp");
% &gt
&lt a href=&lt %=url% &gt &gthello2.jsp&lt /a &gt </P>

hello2.jsp
&lt %@ page session="true" % &gt
&lt %
Integer i= (Integer )session.getvalue("num");
out.println("Num value in session is " i.intvalue());
% &gt </P>

13、在JSP中能发送EMAIL吗
可以使用SUN的专用包：sun.net.smtp包。如下脚本使用SmtpClient类发送EMAIL。
&lt %@ page import="sun.net.smtp.SmtpClient, java.io.*" % &gt
&lt %
String from="<A href="mailto:ybwen@sina.com">ybwen@sina.com</A>";
String to="<A href="mailto:hewenjun@yeah.net">hewenjun@yeah.net</A>, <A href="mailto:lei@who.com.cn">lei@who.com.cn</A>";
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 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);
}
% &gt </P>

14、在SERVLET中我能调用一个JSP错误页吗
当然没问题，如下展示了如何在一个SERVLET控制逻辑单元内调用一个JSP错误页面。
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);
} </P>

public void doPost(HttpServletRequest request,HttpServletResponse response) {
try {
// do something
} catch (Exception ex) {
try {
sendErrorRedirect(request,response,"/jsp/MyErrorPage.jsp",ex);
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