pi3servletcontext.java

mini http server,可以集成嵌入到程序中,实现简单的web功能

/*____________________________________________________________________________*\
 *

 Copyright (c) 1997-2003 John Roy, Holger Zimmermann. All rights reserved.

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 *____________________________________________________________________________*|
 *
 * $Source: /cvsroot/pi3web/Pi3Web_200/Source/Servlet/org/pi3/servlet/core/Pi3ServletContext.java,v $
 * $Date: 2003/05/13 18:42:21 $
 *
 Description:
	Implementation of servlet API ServletContext interface.

\*____________________________________________________________________________*/

package org.pi3.servlet.core;


import java.io.InputStream;
import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;




/**
 * 
 * Defines a set of methods that a servlet uses to communicate with its
 * servlet container, for example, to get the MIME type of a file, dispatch
 * requests, or write to a log file.
 *
 * <p>There is one context per "web application" per Java Virtual Machine. (A
 * "web application" is a collection of servlets and content installed under a
 * specific subset of the server's URL namespace such as <code>/catalog</code>
 * and possibly installed via a <code>.war</code> file.) 
 *
 * <p>In the case of a web application marked "distributed" in its deployment
 * descriptor, there will be one context instance for each virtual machine.
 * In this situation, the  context cannot be used as a location to share global
 * information (because the information won't be truly global). Use an external
 * resource like a database instead.
 *
 * <p>The <code>Pi3ServletContext</code> object is contained within 
 * the {@link Pi3ServletConfig} object, which the Web server provides the
 * servlet when the servlet is initialized.
 *
 * @author 	Holger Zimmermann [[e-mail]]
 * @version	$Revision: 1.7 $
 *
 * @see 	Pi3ServletConfig#getServletContext
 *
 */

final public class Pi3ServletContext implements ServletContext {

	private Hashtable attribs;
	private String root;
	private int hcon;




	/** This constructor is used by the native side */
	protected Pi3ServletContext(int hContainer, String docRoot) {
		root = docRoot;
		hcon = hContainer;
	}




	/** This method is used by the native side */
	protected int getContainer() {
		return hcon;
	}




    /**
     * Returns a <code>ServletContext</code> object that 
     * corresponds to a specified URL on the server.
     *
     * <p>This method allows servlets to gain
     * access to the context for various parts of the server, and as
     * needed obtain {@link Pi3RequestDispatcher} objects from the context.
     * The given path must be absolute (beginning with "/") and is 
     * interpreted based on the server's document root. 
     * 
     * <p>In a security conscious environment, the servlet container may
     * return <code>null</code> for a given URL.
     *       
     * @param uripath 	a <code>String</code> specifying the absolute URL of 
     *			a resource on the server
     *
     * @return		the <code>ServletContext</code> object that
     *			corresponds to the named URL
     *
     * @see 		Pi3RequestDispatcher
     *
     */

	public ServletContext getContext(String uripath) {
	    return (uripath.startsWith("/")) ? this : null;
	}




    /**
     * Returns the major version of the Java Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.x must have this method
     * return the integer 2.
     *
     * @return 		2
     *
     */

	public int getMajorVersion() {
	    return Constants.SERVLET_MAJOR;
	}




    /**
     * Returns the minor version of the Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.1 must have this method
     * return the integer 1.
     *
     * @return 		1
     *
     */

	public int getMinorVersion() {
	    return Constants.SERVLET_MINOR;
	}




    /**
     * Returns the MIME type of the specified file, or <code>null</code> if 
     * the MIME type is not known. The MIME type is determined
     * by the configuration of the servlet container, and may be specified
     * in a web application deployment descriptor. Common MIME
     * types are <code>"text/html"</code> and <code>"image/gif"</code>.
     *
     *
     * @param   file    a <code>String</code> specifying the name
     *			of a file
     *
     * @return 		a <code>String</code> specifying the file's MIME type
     *
     */

	public native String getMimeType(String file);




    /**
     * Returns a URL to the resource that is mapped to a specified
     * path. The path must begin with a "/" and is interpreted
     * as relative to the current context root.
     *
     * <p>This method allows the servlet container to make a resource 
     * available to servlets from any source. Resources 
     * can be located on a local or remote
     * file system, in a database, or in a <code>.war</code> file. 
     *
     * <p>The servlet container must implement the URL handlers
     * and <code>URLConnection</code> objects that are necessary
     * to access the resource.
     *
     * <p>This method returns <code>null</code>
     * if no resource is mapped to the pathname.
     *
     * <p>Some containers may allow writing to the URL returned by
     * this method using the methods of the URL class.
     *
     * <p>The resource content is returned directly, so be aware that 
     * requesting a <code>.jsp</code> page returns the JSP source code.
     * Use a <code>RequestDispatcher</code> instead to include results of 
     * an execution.
     *
     * <p>This method has a different purpose than
     * <code>java.lang.Class.getResource</code>,
     * which looks up resources based on a class loader. This
     * method does not use class loaders.
     * 
     * @param path 				a <code>String</code> specifying
     *						the path to the resource
     *
     * @return 					the resource located at the named path,
     * 						or <code>null</code> if there is no resource
     *						at that path
     *
     * @exception MalformedURLException 	if the pathname is not given in 
     * 						the correct form
     *
     */

	public URL getResource(String path) throws MalformedURLException {
	    String mappedPath = getRealPath(path);
        return new URL("file", null, 0, mappedPath);
	};




    /**
     * Returns the resource located at the named path as
     * an <code>InputStream</code> object.
     *
     * <p>The data in the <code>InputStream</code> can be 
     * of any type or length. The path must be specified according
     * to the rules given in <code>getResource</code>.
     * This method returns <code>null</code> if no resource exists at
     * the specified path. 
     * 
     * <p>Meta-information such as content length and content type
     * that is available via <code>getResource</code>
     * method is lost when using this method.
     *
     * <p>The servlet container must implement the URL handlers
     * and <code>URLConnection</code> objects necessary to access
     * the resource.
     *
     * <p>This method is different from 
     * <code>java.lang.Class.getResourceAsStream</code>,
     * which uses a class loader. This method allows servlet containers 
     * to make a resource available
     * to a servlet from any location, without using a class loader.
     * 
     *
     * @param name 	a <code>String</code> specifying the path
     *			to the resource
     *
     * @return 		the <code>InputStream</code> returned to the 
     *			servlet, or <code>null</code> if no resource
     *			exists at the specified path 
     *
     *
     */

	public InputStream getResourceAsStream(String path) {
        URL url;
        try {
		    url = getResource(path);
		} catch (MalformedURLException e) {
		    return null;
		};

        if (url != null) {
		    InputStream ins;
		    try {
			  ins = url.openStream();
		    } catch (IOException e) {
		        return null;
		    };
			return ins;
		};

		return null;
	};




    /**
     * 
     * Returns a {@link Pi3RequestDispatcher} object that acts
     * as a wrapper for the resource located at the named path.
     * You can use a <code>RequestDispatcher</code> object to forward 
     * a request to the resource or include a resource in a response.