Java/JSP/Errors
Содержание
- 1 Advanced Dynamic Web Content Generation: form error check
- 2 Building a simple error handling page
- 3 Deal with the errors
- 4 Error Handling: compile error in JSP page
- 5 Error without handler
- 6 Jsp Error Bean
- 7 JSP error detected
- 8 JSP Error handler
- 9 JSP error: no such page
- 10 Page with error in JSP directive and actions
- 11 Simple error testing
- 12 Using an Error Page Jsp
- 13 Using the Exception Object in Jsp
Advanced Dynamic Web Content Generation: form error check
/*
Beginning JavaServer Pages
Vivek Chopra, Jon Eaves, Rupert Jones, Sing Li, John T. Bell
ISBN: 0-7645-7485-X
*/
Building a simple error handling page
<HTML>
<HEAD>
<TITLE>Building a simple error handling page.</TITLE>
</HEAD>
<BODY>
<%
try{
int value = 1;
value = value / 0;
}
catch (Exception e){
System.out.println(e.getMessage());
}
%>
</BODY>
</HTML>
Deal with the errors
// generateError.jsp
<%@ page errorPage="processError.jsp" %>
<%-- Declare the page to send errors to --%>
<%-- After clicking the button, it will call itself again the generate error --%>
<%-- This scriptlet checks a hidden field to see whether or not to throw an exception --%>
<%
String hiddenField = request.getParameter("hiddenValue");
if ( hiddenField.equals("error"))
throw new java.lang.NullPointerException();
%>
<HTML>
<HEAD><TITLE>Generate Error</TITLE></HEAD>
<BODY>
This page generates an error when you click the button.<P>
<FORM METHOD="POST" ACTION="generateError.jsp">
<INPUT TYPE="HIDDEN" NAME="hiddenValue" VALUE="error">
<INPUT TYPE="SUBMIT" VALUE="Generate exception!">
</FORM>
</BODY>
</HTML>
//Another JSP file: processError.jsp
<%@ page isErrorPage="true" %>
<HTML>
<HEAD><TITLE> Process Error</TITLE></HEAD>
<BODY>
<% if ( exception != null ) {
out.write("\nAn error occurred. This page is to tell you what you did wrong.\n");
}
else {
out.write("\nYou have reached this page, but no error information is available.\n");
}
%>
</BODY>
</HTML>
Error Handling: compile error in JSP page
/*
Beginning JavaServer Pages
Vivek Chopra, Jon Eaves, Rupert Jones, Sing Li, John T. Bell
ISBN: 0-7645-7485-X
*/
<html>
<head>
<title>Error in Scripting Element</title>
</head>
<body>
<h1>Page with error in scripting element</h1>
<%
int sum= 0;
for { int i=0; i<50; i++ }
sum = sum + i;
%>
</body>
</html>
Error without handler
//File Name: generateErrorNoHandler.jsp
<%-- This scriptlet checks a hidden field to see whether or not to throw an exception --%>
<%
String hiddenField = request.getParameter("hiddenValue");
if ( hiddenField.equals("error"))
throw new java.lang.NullPointerException();
%>
<HTML>
<HEAD><TITLE>Generate Error</TITLE></HEAD>
<BODY>
This page generates an error when you click the button.<P>
<FORM METHOD="POST" ACTION="generateErrorNoHandler.jsp">
<INPUT TYPE="HIDDEN" NAME="hiddenValue" VALUE="error">
<INPUT TYPE="SUBMIT" VALUE="Generate exception!">
</FORM>
</BODY>
</HTML>
Jsp Error Bean
JSP error detected
/*
Beginning JavaServer Pages
Vivek Chopra, Jon Eaves, Rupert Jones, Sing Li, John T. Bell
ISBN: 0-7645-7485-X
*/
JSP Error handler
<%@page isErrorPage="true" %>
<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<html>
<head><title>Sorry about the error</title></head>
<body>
<h2>Sorry, We Erred Handling Your Request</h2>
<strong>Here is information about the error:</strong> <br><br>
The servlet name associated with throwing the exception:
<%-- JSP 2.0 usage only!
<c:out value="${pageContext.errorData.servletName}" /> --%>
<br><br>
The type of exception: <c:out value=
"${requestScope[
\"javax.servlet.jsp.jspException\"].class.name}" />
<br><br>
The request URI:
<%-- JSP 2.0 usage only!
<c:out value="${pageContext.errorData.requestURI}" /> --%>
<br><br>
The exception message:
<c:out value="${pageContext.exception.message}" />
</body>
</html>
JSP error: no such page
/*
Beginning JavaServer Pages
Vivek Chopra, Jon Eaves, Rupert Jones, Sing Li, John T. Bell
ISBN: 0-7645-7485-X
*/
Page with error in JSP directive and actions
/*
Beginning JavaServer Pages
Vivek Chopra, Jon Eaves, Rupert Jones, Sing Li, John T. Bell
ISBN: 0-7645-7485-X
*/
Simple error testing
//File: index.jsp
<%@ page errorPage="errPage.jsp" %>
<HTML>
<HEAD><TITLE> Simple error testing </TITLE></HEAD>
<BODY>
<%!
String nullString = null;
%>
<%-- Intentionally invoking a NullPointerException --%>
The length of the nullString is <%= nullString.length() %>
</BODY>
</HTML>
/////////////////////////////////////////////////////
//File: errPage.jsp
<%@ page isErrorPage="true" %>
Uncaught exception <%= exception %> has been encountered!
Using an Error Page Jsp
//File: index.jsp
<%@ page errorPage="errorPage.jsp" %>
<HTML>
<HEAD>
<TITLE>Using an Error Page</TITLE>
</HEAD>
<BODY>
<H1>Using an Error Page</H1>
<%
int value = 1;
value = value / 0;
%>
</BODY>
</HTML>
//File: errorPage.jsp
<%@ page isErrorPage="true" %>
<HTML>
<HEAD>
<TITLE>An Error Page</TITLE>
</HEAD>
<BODY>
<H1>An Error Page</H1>
There was an error! Don"t Panic!!!
<BR>
Consult your physician immediately.
</BODY>
</HTML>
