java/jakarta/servlet/jsp/JspPage.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package jakarta.servlet.jsp;

import jakarta.servlet.Servlet;

/**
 * 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.
 * <p>
 * <B>Two plus One Methods</B>
 * <p>
 * The interface defines a protocol with 3 methods; only two of them: jspInit() and jspDestroy() are part of this
 * interface as the signature of the third method: _jspService() depends on the specific protocol used and cannot be
 * expressed in a generic way in Java.
 * <p>
 * A class implementing this interface is responsible for invoking the above methods at the appropriate time based on
 * the corresponding Servlet-based method invocations.
 * <p>
 * The jspInit() and jspDestroy() methods can be defined by a JSP author, but the _jspService() method is defined
 * automatically by the JSP processor based on the contents of the JSP page.
 * <p>
 * <B>_jspService()</B>
 * <p>
 * The _jspService()method corresponds to the body of the JSP page. This method is defined automatically by the JSP
 * container and should never be defined by the JSP page author.
 * <p>
 * If a superclass is specified using the extends attribute, that superclass may choose to perform some actions in its
 * service() method before or after calling the _jspService() method. See using the extends attribute in the JSP_Engine
 * chapter of the JSP specification.
 * <p>
 * The specific signature depends on the protocol supported by the JSP page.
 *
 * <pre>
 * public void _jspService(<em>ServletRequestSubtype</em> request,
 *                             <em>ServletResponseSubtype</em> response)
 *        throws ServletException, IOException;
 * </pre>
 */


public interface JspPage extends Servlet {

    /**
     * The jspInit() method is invoked when the JSP page is initialized. It is the responsibility of the JSP
     * implementation (and of the class mentioned by the extends attribute, if present) that at this point invocations
     * to the getServletConfig() method will return the desired value.
     * <p>
     * A JSP page can override this method by including a definition for it in a declaration element.
     * <p>
     * A JSP page should redefine the init() method from Servlet.
     */
    void jspInit();

    /**
     * The jspDestroy() method is invoked when the JSP page is about to be destroyed.
     * <p>
     * A JSP page can override this method by including a definition for it in a declaration element.
     * <p>
     * A JSP page should redefine the destroy() method from Servlet.
     */
    void jspDestroy();

}