Module jakarta.servlet.jsp

Package jakarta.servlet.jsp

Classes and interfaces for the Core JSP 3.1 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);
    }
}