servletcontext.java

windows下的JAVA虚拟机

/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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;

import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Set;


/**
 * 
 * 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>ServletContext</code> object is contained within 
 * the {@link ServletConfig} object, which the Web server provides the
 * servlet when the servlet is initialized.
 *
 * @author 	Various
 * @version 	$Version$
 *
 * @see 	Servlet#getServletConfig
 * @see 	ServletConfig#getServletContext
 *
 */

public interface ServletContext {


    /**
     * 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 RequestDispatcher} objects from the context.
     * The given path must be begin with "/", is interpreted relative 
     * to the server's document root and is matched against the context roots of
     * other web applications hosted on this container.
     * 
     * <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 context path of
     *			another web application in the container.
     * @return		the <code>ServletContext</code> object that
     *			corresponds to the named URL, or null if either
			none exists or the container wishes to restrict 
     * 			this access.
     *
     * @see 		RequestDispatcher
     *
     */

    public ServletContext getContext(String uripath);
    
    

    /**
     * Returns the major version of the Java Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.4 must have this method
     * return the integer 2.
     *
     * @return 		2
     *
     */
    
    public int getMajorVersion();
    
    

    /**
     * Returns the minor version of the Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.4 must have this method
     * return the integer 4.
     *
     * @return 		4
     *
     */

    public int getMinorVersion();
    
    

    /**
     * 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 String getMimeType(String file);
    
    /**
    * Returns a directory-like listing of all the paths to resources within the web application whose longest sub-path
    * matches the supplied path argument. Paths indicating subdirectory paths end with a '/'. The returned paths are all 
    * relative to the root of the web application and have a leading '/'. For example, for a web application 
    * containing<br><br>

    * /welcome.html<br>
    * /catalog/index.html<br>
    * /catalog/products.html<br>
    * /catalog/offers/books.html<br>
    * /catalog/offers/music.html<br>
    * /customer/login.jsp<br>
    * /WEB-INF/web.xml<br>
    * /WEB-INF/classes/com.acme.OrderServlet.class,<br><br>
    *
    * getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}<br>
    * getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.<br>
	   


    *@param path		the partial path used to match the resources,
    *				which must start with a /
    *@return a Set containing the directory listing, or null if there are no resources in the web application whose path
	* begins with the supplied path.

    * @since Servlet 2.3
    */
    
    public Set getResourcePaths(String path);
    
    

    /**
     * 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;
    
    

    /**
     * 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 path 	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);
    



    /**
     * 
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the resource located at the given path.
     * A <code>RequestDispatcher</code> object can be used to forward 
     * a request to the resource or to include the resource in a response.
     * The resource can be dynamic or static.
     *
     * <p>The pathname must begin with a "/" and is interpreted as relative
     * to the current context root.  Use <code>getContext</code> to obtain
     * a <code>RequestDispatcher</code> for resources in foreign contexts.
     * This method returns <code>null</code> if the <code>ServletContext</code>
     * cannot return a <code>RequestDispatcher</code>.
     *
     * @param path 	a <code>String</code> specifying the pathname
     *			to the resource
     *
     * @return 		a <code>RequestDispatcher</code> object
     *			that acts as a wrapper for the resource
     *			at the specified path, or <code>null</code> if 
     *			the <code>ServletContext</code> cannot return
     *			a <code>RequestDispatcher</code>
     *
     * @see 		RequestDispatcher
     * @see 		ServletContext#getContext
     *
     */

    public RequestDispatcher getRequestDispatcher(String path);



    /**
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the named servlet.
     *
     * <p>Servlets (and JSP pages also) may be given names via server 
     * administration or via a web application deployment descriptor.
     * A servlet instance can determine its name using 
     * {@link ServletConfig#getServletName}.
     *
     * <p>This method returns <code>null</code> if the 
     * <code>ServletContext</code>
     * cannot return a <code>RequestDispatcher</code> for any reason.
     *
     * @param name 	a <code>String</code> specifying the name
     *			of a servlet to wrap
     *
     * @return 		a <code>RequestDispatcher</code> object
     *			that acts as a wrapper for the named servlet,
     *			or <code>null</code> if the <code>ServletContext</code>
     *			cannot return a <code>RequestDispatcher</code>
     *
     * @see 		RequestDispatcher
     * @see 		ServletContext#getContext
     * @see 		ServletConfig#getServletName
     *
     */

    public RequestDispatcher getNamedDispatcher(String name);
    
    
    
    
    /**
     *
     * @deprecated	As of Java Servlet API 2.1, with no direct replacement.
     *
     * <p>This method was originally defined to retrieve a servlet
     * from a <code>ServletContext</code>. In this version, this method 
     * always returns <code>null</code> and remains only to preserve 
     * binary compatibility. This method will be permanently removed 
     * in a future version of the Java Servlet API.