Exception Handling in JSP:
The exception is normally an object that is thrown at runtime. Exception
Handling is the process to handle the runtime errors. There may occur exception
any time in your web application. So handling exceptions is a safer side for the
web developer. In JSP, there are two ways to perform exception handling:
1)By errorPage and isErrorPage attributes of page directive
2)By <error-page> element in web.xml file
Example of exception handling in jsp by the elements of page directive:
In this case, you must define and create a page to handle the exceptions, as in
the error.jsp page. The pages where may occur exception, define the errorPage
attribute of page directive, as in the process.jsp page.
There are 3 files:
index.jsp for input values
process.jsp for dividing the two numbers and displaying the result
error.jsp for handling the exception
index.jsp:
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<form action="process.jsp"> No1:<input type="text" name="n1" /><br/><br/> No1:<input type="text" name="n2" /><br/><br/> <input type="submit" value="divide"/> </form> |
process.jsp:
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<%@ page errorPage="error.jsp" %> <% String num1=request.getParameter("n1"); String num2=request.getParameter("n2"); int a=Integer.parseInt(num1); int b=Integer.parseInt(num2); int c=a/b; out.print("division of numbers is: "+c); %> |
error.jsp:
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<%@ page isErrorPage="true" %> <h3>Sorry an exception occured!</h3> Exception is: <%= exception %> |
Example of exception handling in jsp by
specifying the error-page element in web.xml file:
This approach is better because you don't need to specify the errorPage
attribute in each jsp page. Specifying the single entry in the web.xml file will
handle the exception. In this case, either specify exception-type or error-code
with the location element. If you want to handle all the exception, you will
have to specify the java.lang.Exception in the exception-type element. Let's see
the simple example:
There are 4 files:
web.xml file for specifying the error-page element
index.jsp for input values
process.jsp for dividing the two numbers and displaying the result
error.jsp for displaying the exception
1) web.xml file if you want to handle any exception
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<web-app> <error-page> <exception-type>java.lang.Exception</exception-type> <location>/error.jsp</location> </error-page> </web-app> |
This approach is better if you want to handle any exception. If you know any
specific error code and you want to handle that exception, specify the
error-code element instead of exception-type as given below:
1) web.xml file if you want to handle the exception for a specific error
code
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<web-app> <error-page> <error-code>500</error-code> <location>/error.jsp</location> </error-page> </web-app> |
2) index.jsp
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<form action="process.jsp"> No1:<input type="text" name="n1" /><br/><br/> No1:<input type="text" name="n2" /><br/><br/> <input type="submit" value="divide"/> </form> |
3) process.jsp
Now, you don't need to specify the errorPage attribute of page directive in the
jsp page.
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<%@ page errorPage="error.jsp" %> <% String num1=request.getParameter("n1"); String num2=request.getParameter("n2"); int a=Integer.parseInt(num1); int b=Integer.parseInt(num2); int c=a/b; out.print("division of numbers is: "+c); %> |
4) error.jsp
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<%@ page isErrorPage="true" %> <h3>Sorry an exception occured!</h3> Exception is: <%= exception %> |