zkoss/zk

/* RequestContext.java

    Purpose:
        
    Description:
        
    History:
        Thu Aug 30 12:32:50     2007, Created by tomyeh

Copyright (C) 2007 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
    This program is distributed under LGPL Version 2.1 in the hope that
    it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.web.servlet.xel;

import java.io.IOException;
import java.io.Writer;

import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.zkoss.xel.VariableResolver;

/**
 * The context used to simplify the signatures of XEL function.
 *
 * <p>It is designed to make the signature of XEL functions
 * (see {@link org.zkoss.web.fn.ServletFns}) simpler.
 * For example, {@link org.zkoss.web.fn.ServletFns#getCurrentContext} requires
 * no argument, since it assumes the current context can be retrieved
 * from {@link RequestContexts#getCurrent}.
 *
 * @author tomyeh
 * @since 3.0.0
 */
public interface RequestContext {
    /** Returns the writer, never null.
     */
    public Writer getOut() throws IOException;

    /** Returns the request, or null if not available.
     */
    public ServletRequest getRequest();

    /** Returns the response, or null if not available.
     */
    public ServletResponse getResponse();

    /** Returns the request, or null if not available.
     */
    public ServletContext getServletContext();

    /** Returns the variable resolver.
     */
    public VariableResolver getVariableResolver();
}