Module jakarta.servlet.jsp

Package jakarta.servlet.jsp

package jakarta.servlet.jsp

Classes and interfaces for the Core JSP 4.0 API.

References in this document to JSP refer to the Jakarta Server Pages unless otherwise noted.

The jakarta.servlet.jsp package contains a number of classes and interfaces that describe and define the contracts between a JSP page implementation class and the runtime environment provided for an instance of such a class by a conforming JSP container.

JSP Page Implementation Object Contract

This section describes the basic contract between a JSP Page implementation object and its container.

The main contract is defined by the classes JspPage and HttpJspPage. The JspFactory class describes the mechanism to portably instantiate all needed runtime objects, and JspEngineInfo provides basic information on the current JSP container. Class JspApplicationContext stores application-scoped information relevant to JSP containers. It was added in JSP 2.1 to support the integration of the unified Expression Language.

None of these classes are intended to be used by JSP page authors; an example of how these classes may be used is included below.

Implicit Objects

The PageContext object and the JspWriter are available by default as implicit objects.

Exceptions

The JspException class is the base class for all JSP exceptions. The JspTagException and SkipPageException exceptions are used by the tag extension mechanism.

For JSP error pages, the ErrorData class encapsulates information about the error.

An Implementation Example

An instance of an implementation dependent subclass of the PageContext abstract base class can be created by a JSP implementation class at the beginning of it's _jspService() method via an implementation default JspFactory.

Here is one example of how to use these classes

public class foo implements Servlet {

// ...

public void _jspService(HttpServletRequest request,
                        HttpServletResponse response)
       throws IOException, ServletException {

    JspFactory  factory     = JspFactory.getDefaultFactory();
    PageContext pageContext = factory.getPageContext(
                                        this,
                                        request,
                                        response,
                                        null,  // errorPageURL
                                        false, // needsSession
                                        JspWriter.DEFAULT_BUFFER,
                                        true   // autoFlush
                                );

    // initialize implicit variables for scripting env ...

    HttpSession session = pageContext.getSession();
    JspWriter   out     = pageContext.getOut();
    Object      page    = this;

    try {
        // body of translated JSP here ...
    } catch (Exception e) {
        out.clear();
        pageContext.handlePageException(e);
    } finally {
        out.close();
          factory.releasePageContext(pageContext);
    }
}

Related Packages

Package	Description
jakarta.servlet.jsp.el	Provides the ELResolver classes that define the object resolution rules that must be supported by a JSP container with the unified Expression Language.
jakarta.servlet.jsp.tagext	Classes and interfaces for the definition of Jakarta Server Pages Tag Libraries.

Class	Description
ErrorData	Contains information about an error, for error pages.
HttpJspPage	The HttpJspPage interface describes the interaction that a JSP Page Implementation Class must satisfy when using the HTTP protocol.
JspApplicationContext	Stores application-scoped information relevant to JSP containers.
JspContext	JspContext serves as the base class for the PageContext class and abstracts all information that is not specific to servlets.
JspEngineInfo	The JspEngineInfo is an abstract class that provides information on the current JSP engine.
JspException	A generic exception known to the JSP engine; uncaught JspExceptions will result in an invocation of the errorpage machinery.
JspFactory	The JspFactory is an abstract class that defines a number of factory methods available to a JSP page at runtime for the purposes of creating instances of various interfaces and classes used to support the JSP implementation.
JspPage	The JspPage interface describes the generic interaction that a JSP Page Implementation class must satisfy; pages that use the HTTP protocol are described by the HttpJspPage interface.
JspTagException	Exception to be used by a Tag Handler to indicate some unrecoverable error.
JspWriter	The actions and template data in a JSP page is written using the JspWriter object that is referenced by the implicit variable out which is initialized automatically using methods in the PageContext object.
PageContext	PageContext extends JspContext to provide useful context information for when JSP technology is used in a Servlet environment.
SkipPageException	Exception to indicate the calling page must cease evaluation.