/*
 * 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);
}
