Java Doc for JspApplicationContext.java in  » EJB-Server-GlassFish » servlet » javax » servlet » jsp » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The JSP container must create a single instance of JspApplicationContext for each ServletContext instance.

An instance of JspApplicationContext is obtained by invoking the static JspFactory.getJspApplicationContext method, passing the ServletContext of the corresponding web application.

The JspApplicationContext provides the following services to JSP applications:

• Allows registration of ELResolvers, which are used to resolve variables in EL expressions contained in JSP pages and tag files.
• Provides an instance of ExpressionFactory for those applications or frameworks that need to perform programmatic evaluation of EL expressions instead of allowing the JSP container to do it for them.
• Allows the attachment of ELContextListener instances for notification whenever a new ELContext is created. This is necessary when an application wishes to make custom context objects available to their pluggable ELResolvers.

At a minimum, the ELContext objects created will contain a reference to the JspContext for this request, which is added by the JSP container. This is sufficient for all the default ELResolvers listed in JspApplicationContext.addELResolver . Note that JspContext.class is used as the key to ELContext.putContext() for the JspContext object reference.

This method is generally used by frameworks and applications that register their own ELResolver that needs context other than JspContext.

For example, in the EL expression ${employee.lastName}, an ELResolver determines what object "employee" references and how to find its "lastName" property.

When evaluating an expression, the JSP container will consult a set of standard resolvers as well as any resolvers registered via this method.

At a minimum, the ELContext objects created will contain a reference to the JspContext for this request, which is added by the JSP container. This is sufficient for all the default ELResolvers listed in JspApplicationContext.addELResolver . Note that JspContext.class is used as the key to ELContext.putContext() for the JspContext object reference.

This method is generally used by frameworks and applications that register their own ELResolver that needs context other than JspContext. The listener will typically add the necessary context to the ELContext provided in the event object. Registering a listener that adds context allows the ELResolvers in the stack to access the context they need when they do a resolution.

For example, in the EL expression ${employee.lastName}, an ELResolver determines what object "employee" references and how to find its "lastName" property.

When evaluating an expression, the JSP container will consult a set of standard resolvers as well as any resolvers registered via this method. The set of resolvers are consulted in the following order:

• javax.servlet.jsp.el.ImplicitObjectELResolver
• ELResolvers registered via this method, in the order in which they are registered.
• javax.el.MapELResolver
• javax.el.ListELResolver
• javax.el.ArrayELResolver
• javax.el.BeanELResolver
• javax.servlet.jsp.el.ScopedAttributeELResolver

It is illegal to register an ELResolver after the application has received any request from the client. If an attempt is made to register an ELResolver after that time, an IllegalStateException is thrown.

It is not possible to remove an ELResolver registered with this method, once it has been registered.