/*
 * 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 javax.servlet.jsp;

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

/**
 * <p>
 * The JspFactory is an abstract class that defines a number of factory
 * methods available to a JSP page at runtime for the purposes of creating
 * instances of various interfaces and classes used to support the JSP
 * implementation.
 * <p>
 * A conformant JSP Engine implementation will, during it's initialization
 * instantiate an implementation dependent subclass of this class, and make
 * it globally available for use by JSP implementation classes by registering
 * the instance created with this class via the
 * static <code> setDefaultFactory() </code> method.
 * <p>
 * The PageContext and the JspEngineInfo classes are the only
 * implementation-dependent classes that can be created from the factory.
 * <p>
 * JspFactory objects should not be used by JSP page authors.
 */

public abstract class JspFactory {

    private static volatile JspFactory deflt = null;

    /**
     * Sole constructor. (For invocation by subclass constructors,
     * typically implicit.)
     */
    public JspFactory() {
        // NOOP by default
    }

    /**
     * <p>
     * set the default factory for this implementation. It is illegal for
     * any principal other than the JSP Engine runtime to call this method.
     * </p>
     *
     * @param deflt        The default factory implementation
     */

    public static void setDefaultFactory(JspFactory deflt) {
        JspFactory.deflt = deflt;
    }

    /**
     * Returns the default factory for this implementation.
     *
     * @return the default factory for this implementation
     */

    public static JspFactory getDefaultFactory() {
        return deflt;
    }

    /**
     * <p>
     * obtains an instance of an implementation dependent
     * javax.servlet.jsp.PageContext abstract class for the calling Servlet
     * and currently pending request and response.
     * </p>
     *
     * <p>
     * This method is typically called early in the processing of the
     * _jspService() method of a JSP implementation class in order to
     * obtain a PageContext object for the request being processed.
     * </p>
     * <p>
     * Invoking this method shall result in the PageContext.initialize()
     * method being invoked. The PageContext returned is properly initialized.
     * </p>
     * <p>
     * All PageContext objects obtained via this method shall be released
     * by invoking releasePageContext().
     * </p>
     *
     * @param servlet      the requesting servlet
     * @param request      the current request pending on the servlet
     * @param response     the current response pending on the servlet
     * @param errorPageURL the URL of the error page for the requesting JSP, or
     *                         null
     * @param needsSession true if the JSP participates in a session
     * @param buffer       size of buffer in bytes, {@link JspWriter#NO_BUFFER}
     *                         if no buffer, {@link JspWriter#DEFAULT_BUFFER}
     *                         if implementation default.
     * @param autoflush    should the buffer autoflush to the output stream on
     *                         buffer overflow, or throw an IOException?
     *
     * @return the page context
     *
     * @see javax.servlet.jsp.PageContext
     */

    public abstract PageContext getPageContext(Servlet servlet,
            ServletRequest request, ServletResponse response,
            String errorPageURL, boolean needsSession, int buffer,
            boolean autoflush);

    /**
     * <p>
     * called to release a previously allocated PageContext object.
     * Results in PageContext.release() being invoked.
     * This method should be invoked prior to returning from the _jspService()
     * method of a JSP implementation class.
     * </p>
     *
     * @param pc A PageContext previously obtained by getPageContext()
     */
    public abstract void releasePageContext(PageContext pc);

    /**
     * <p>
     * called to get implementation-specific information on the current JSP
     * engine.
     * </p>
     *
     * @return a JspEngineInfo object describing the current JSP engine
     */

    public abstract JspEngineInfo getEngineInfo();

    /**
     * <p>
     * Obtain the <code>JspApplicationContext</code> instance that was
     * associated within the passed <code>ServletContext</code> for this web
     * application.
     * </p>
     *
     * @param context the current web application's <code>ServletContext</code>
     * @return <code>JspApplicationContext</code> instance
     * @since JSP 2.1
     */
    public abstract JspApplicationContext getJspApplicationContext(
            ServletContext context);
}
