javax.servlet.jsp.JspApplicationContext Maven / Gradle / Ivy
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package javax.servlet.jsp;
import javax.el.ELResolver;
import javax.el.ExpressionFactory;
import javax.el.ELContextListener;
/**
* Stores application-scoped information relevant to JSP containers.
*
* The JSP container must create a single instance of
* JspApplicationContext for each
* ServletContext instance.
*
* An instance of JspApplicationContext is obtained by
* invoking the static {@link 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.
*
*
*
* @see javax.servlet.ServletContext
* @see JspFactory
* @see javax.el.ELResolver
* @see javax.el.ExpressionFactory
* @see javax.el.ELContextListener
* @since JSP 2.1
*/
public interface JspApplicationContext {
/**
* Adds an ELResolver to affect the way EL variables
* and properties are resolved for EL expressions appearing in JSP pages
* and tag files.
*
* 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:
*
* - {@link javax.servlet.jsp.el.ImplicitObjectELResolver}
* ELResolvers registered via this method, in the
* order in which they are registered.- {@link javax.el.MapELResolver}
* - {@link javax.el.ListELResolver}
* - {@link javax.el.ArrayELResolver}
* - {@link javax.el.BeanELResolver}
* - {@link 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.
* This restriction is
* in place to allow the JSP container to optimize for the common
* case where no additional ELResolvers are in the chain,
* aside from the standard ones. It is permissible to add
* ELResolvers before or after initialization to
* a CompositeELResolver that is already in the chain.
*
* It is not possible to remove an ELResolver registered
* with this method, once it has been registered.
*
* @param resolver The new ELResolver
* @throws IllegalStateException if an attempt is made to
* call this method after all ServletContextListeners
* have had their contextInitialized methods invoked.
*/
public void addELResolver(ELResolver resolver);
/**
* Returns a factory used to create ValueExpressions and
* MethodExpressions so that EL expressions can be
* parsed and evaluated.
*
* @return A concrete implementation of the
* an ExpressionFactory.
*/
public ExpressionFactory getExpressionFactory();
/**
* Registers a ELContextListeners so that context objects
* can be added whenever a new ELContext is created.
*
* 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 {@link #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.
*
* @param listener The listener to be notified when a new
* ELContext is created.
*/
public void addELContextListener(ELContextListener listener);
}