Explain the scope of JSP objects.

Scope of JSP objects:
The availability of a JSP object for use from a particular place of the application is defined as the scope of that JSP object. Every object created in a JSP page will have a scope. Object scope in JSP is segregated into four parts and they are page, request, session and application.

* page
‘page’ scope means, the JSP object can be accessed only from within the same page where it was created. The default scope for JSP objects created using tag is page. JSP implicit objects out, exception, response, pageContext, config and page have ‘page’ scope.
* request
A JSP object created using the ‘request’ scope can be accessed from any pages that serves that request. More than one page can serve a single request. The JSP object will be bound to the request object. Implicit object request has the ‘request’ scope.
* session
’session’ scope means, the JSP object is accessible from pages that belong to the same session from where it was created. The JSP object that is created using the session scope is bound to the session object. Implicit object session has the ’session’ scope.
* application
A JSP object created using the ‘application’ scope can be accessed from any pages across the application. The JSP object is bound to the application object. Implicit object application has the ‘application’ scope.

How to pre-compile JSP?

Add jsp_precompile as a request parameter and send a request to the JSP file. This will make the jsp pre-compile. Why it is mentioned as pre compile instead of compilation is that, the request is not served. That is, the JSP will not be executed and the request will not be serviced. Just it will be compiled and the implementation class will be generated.

The jsp_precompile parameter may have no value, or may have values true or false. It should not have any other values like ?jsp_precompile=yes – this will result in HTTP error 500.

So the example for query strings to pre compile jsp files are
?jsp_precompile
?jsp_precompile=true
?jsp_precompile=false
?foobar=foobaz&jsp_precompile=true
?foobar=foobaz&jsp_precompile=false

How to do pre compile for a bunch of JSP files? for all JSPs in a folder or application?
There are no special features available for this in the JSP specification. But the application servers (JSP containers) provide methods to do this on their own way. At the end of this tutorial we will see how to pre compile JSP files for Apache Tomcat 6.

But if you want to pre compile in server independent manner you have to use jsp_precompile request parameter and no other option available. To do it for the whole application, you can custome write a servlet or jsp file which will raise a request for all the JSPs available with jsp_precompile added as parameter.