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  /*
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
   *
   * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.
   *
   * The contents of this file are subject to the terms of either the GNU
   * General Public License Version 2 only ("GPL") or the Common Development
   * and Distribution License("CDDL") (collectively, the "License").  You
   * may not use this file except in compliance with the License.  You can
  * obtain a copy of the License at
  * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
  * or packager/legal/LICENSE.txt.  See the License for the specific
  * language governing permissions and limitations under the License.
  *
  * When distributing the software, include this License Header Notice in each
  * file and include the License file at packager/legal/LICENSE.txt.
  *
  * GPL Classpath Exception:
  * Oracle designates this particular file as subject to the "Classpath"
  * exception as provided by Oracle in the GPL Version 2 section of the License
  * file that accompanied this code.
  *
  * Modifications:
  * If applicable, add the following below the License Header, with the fields
  * enclosed by brackets [] replaced by your own identifying information:
  * "Portions Copyright [year] [name of copyright owner]"
  *
  * Contributor(s):
  * If you wish your version of this file to be governed by only the CDDL or
  * only the GPL Version 2, indicate your decision by adding "[Contributor]
  * elects to include this software in this distribution under the [CDDL or GPL
  * Version 2] license."  If you don't indicate a single choice of license, a
  * recipient has the option to distribute your version of this file under
  * either the CDDL, the GPL Version 2 or to extend the choice of license to
  * its licensees as provided above.  However, if you add GPL Version 2 code
  * and therefore, elected the GPL Version 2 license, then the option applies
  * only if the new code is made subject to such option by the copyright
  * holder.
  *
  *
  * This file incorporates work covered by the following copyright and
  * permission notice:
  *
  * 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.http;
 
 
Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site. A subclass of HttpServlet must override at least one method, usually one of these:
  • doGet, if the servlet supports HTTP GET requests
  • doPost, for HTTP POST requests
  • doPut, for HTTP PUT requests
  • doDelete, for HTTP DELETE requests
  • init and destroy, to manage resources that are held for the life of the servlet
  • getServletInfo, which the servlet uses to provide information about itself

There's almost no reason to override the service method. service handles standard HTTP requests by dispatching them to the handler methods for each HTTP request type (the doXXX methods listed above).

Likewise, there's almost no reason to override the doOptions and doTrace methods.

Servlets typically run on multithreaded servers, so be aware that a servlet must handle concurrent requests and be careful to synchronize access to shared resources. Shared resources include in-memory data such as instance or class variables and external objects such as files, database connections, and network connections. See the Java Tutorial on Multithreaded Programming for more information on handling multiple threads in a Java program.

Author(s):
Various
public abstract class HttpServlet extends GenericServlet
    implements java.io.Serializable
    private static final String METHOD_DELETE = "DELETE";
    private static final String METHOD_HEAD = "HEAD";
    private static final String METHOD_GET = "GET";
    private static final String METHOD_OPTIONS = "OPTIONS";
    private static final String METHOD_POST = "POST";
    private static final String METHOD_PUT = "PUT";
    private static final String METHOD_TRACE = "TRACE";
    private static final String HEADER_IFMODSINCE = "If-Modified-Since";
    private static final String HEADER_LASTMOD = "Last-Modified";
    
    private static final String LSTRING_FILE =
	"javax.servlet.http.LocalStrings";
    private static ResourceBundle lStrings =
	ResourceBundle.getBundle();
   
   
   
    
    
Does nothing, because this is an abstract class.
    public HttpServlet() { }
    
    

    
Called by the server (via the service method) to allow a servlet to handle a GET request.

Overriding this method to support a GET request also automatically supports an HTTP HEAD request. A HEAD request is a GET request that returns no body in the response, only the request header fields.

When overriding this method, read the request data, write the response headers, get the response's writer or output stream object, and finally, write the response data. It's best to include content type and encoding. When using a PrintWriter object to return the response, set the content type before accessing the PrintWriter object.

The servlet container must write the headers before committing the response, because in HTTP the headers must be sent before the response body.

Where possible, set the Content-Length header (with the javax.servlet.ServletResponse.setContentLength(int) method), to allow the servlet container to use a persistent connection to return its response to the client, improving performance. The content length is automatically set if the entire response fits inside the response buffer.

When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.

The GET method should be safe, that is, without any side effects for which users are held responsible. For example, most form queries have no side effects. If a client request is intended to change stored data, the request should use some other HTTP method.

The GET method should also be idempotent, meaning that it can be safely repeated. Sometimes making a method safe also makes it idempotent. For example, repeating queries is both safe and idempotent, but buying a product online or modifying data is neither safe nor idempotent.

If the request is incorrectly formatted, doGet returns an HTTP "Bad Request" message.

Parameters:
req an HttpServletRequest object that contains the request the client has made of the servlet
resp an HttpServletResponse object that contains the response the servlet sends to the client
Throws:
java.io.IOException if an input or output error is detected when the servlet handles the GET request
javax.servlet.ServletException if the request for the GET could not be handled
See also:
javax.servlet.ServletResponse.setContentType(java.lang.String)
    protected void doGet(HttpServletRequest reqHttpServletResponse resp)
    {
	String protocol = req.getProtocol();
	String msg = .getString("http.method_get_not_supported");
	if (protocol.endsWith("1.1")) {
else {
	}
    }





    
Returns the time the HttpServletRequest object was last modified, in milliseconds since midnight January 1, 1970 GMT. If the time is unknown, this method returns a negative number (the default).

Servlets that support HTTP GET requests and can quickly determine their last modification time should override this method. This makes browser and proxy caches work more effectively, reducing the load on server and network resources.

Parameters:
req the HttpServletRequest object that is sent to the servlet
Returns:
a long integer specifying the time the HttpServletRequest object was last modified, in milliseconds since midnight, January 1, 1970 GMT, or -1 if the time is not known
    protected long getLastModified(HttpServletRequest req) {
	return -1;
    }




    

Receives an HTTP HEAD request from the protected service method and handles the request. The client sends a HEAD request when it wants to see only the headers of a response, such as Content-Type or Content-Length. The HTTP HEAD method counts the output bytes in the response to set the Content-Length header accurately.

If you override this method, you can avoid computing the response body and just set the response headers directly to improve performance. Make sure that the doHead method you write is both safe and idempotent (that is, protects itself from being called multiple times for one HTTP HEAD request).

If the HTTP HEAD request is incorrectly formatted, doHead returns an HTTP "Bad Request" message.

Parameters:
req the request object that is passed to the servlet
resp the response object that the servlet uses to return the headers to the clien
Throws:
java.io.IOException if an input or output error occurs
javax.servlet.ServletException if the request for the HEAD could not be handled
    protected void doHead(HttpServletRequest reqHttpServletResponse resp)
    {
	NoBodyResponse response = new NoBodyResponse(resp);
	doGet(reqresponse);
        response.setContentLength();
    }
    




    
Called by the server (via the service method) to allow a servlet to handle a POST request. The HTTP POST method allows the client to send data of unlimited length to the Web server a single time and is useful when posting information such as credit card numbers.

When overriding this method, read the request data, write the response headers, get the response's writer or output stream object, and finally, write the response data. It's best to include content type and encoding. When using a PrintWriter object to return the response, set the content type before accessing the PrintWriter object.

The servlet container must write the headers before committing the response, because in HTTP the headers must be sent before the response body.

Where possible, set the Content-Length header (with the javax.servlet.ServletResponse.setContentLength(int) method), to allow the servlet container to use a persistent connection to return its response to the client, improving performance. The content length is automatically set if the entire response fits inside the response buffer.

When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.

This method does not need to be either safe or idempotent. Operations requested through POST can have side effects for which the user can be held accountable, for example, updating stored data or buying items online.

If the HTTP POST request is incorrectly formatted, doPost returns an HTTP "Bad Request" message.

Parameters:
req an HttpServletRequest object that contains the request the client has made of the servlet
resp an HttpServletResponse object that contains the response the servlet sends to the client
Throws:
java.io.IOException if an input or output error is detected when the servlet handles the request
javax.servlet.ServletException if the request for the POST could not be handled
See also:
javax.servlet.ServletOutputStream
javax.servlet.ServletResponse.setContentType(java.lang.String)
    protected void doPost(HttpServletRequest reqHttpServletResponse resp)
    {
	String protocol = req.getProtocol();
	String msg = .getString("http.method_post_not_supported");
	if (protocol.endsWith("1.1")) {
else {
	}
    }




    
Called by the server (via the service method) to allow a servlet to handle a PUT request. The PUT operation allows a client to place a file on the server and is similar to sending a file by FTP.

When overriding this method, leave intact any content headers sent with the request (including Content-Length, Content-Type, Content-Transfer-Encoding, Content-Encoding, Content-Base, Content-Language, Content-Location, Content-MD5, and Content-Range). If your method cannot handle a content header, it must issue an error message (HTTP 501 - Not Implemented) and discard the request. For more information on HTTP 1.1, see RFC 2616 .

This method does not need to be either safe or idempotent. Operations that doPut performs can have side effects for which the user can be held accountable. When using this method, it may be useful to save a copy of the affected URL in temporary storage.

If the HTTP PUT request is incorrectly formatted, doPut returns an HTTP "Bad Request" message.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
resp the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the PUT request
javax.servlet.ServletException if the request for the PUT cannot be handled
  
    protected void doPut(HttpServletRequest reqHttpServletResponse resp)
    {
	String protocol = req.getProtocol();
	String msg = .getString("http.method_put_not_supported");
	if (protocol.endsWith("1.1")) {
else {
	}
    }




    
Called by the server (via the service method) to allow a servlet to handle a DELETE request. The DELETE operation allows a client to remove a document or Web page from the server.

This method does not need to be either safe or idempotent. Operations requested through DELETE can have side effects for which users can be held accountable. When using this method, it may be useful to save a copy of the affected URL in temporary storage.

If the HTTP DELETE request is incorrectly formatted, doDelete returns an HTTP "Bad Request" message.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
resp the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the DELETE request
javax.servlet.ServletException if the request for the DELETE cannot be handled
     
    protected void doDelete(HttpServletRequest req,
			    HttpServletResponse resp)
    {
	String protocol = req.getProtocol();
	String msg = .getString("http.method_delete_not_supported");
	if (protocol.endsWith("1.1")) {
else {
	}
    }
    
    private Method[] getAllDeclaredMethods(Class<?> c) {
        if (c.equals(javax.servlet.http.HttpServlet.class)) {
            return null;
        }
        Method[] parentMethods = getAllDeclaredMethods(c.getSuperclass());
        Method[] thisMethods = c.getDeclaredMethods();
        if ((parentMethods != null) && (parentMethods.length > 0)) {
            Method[] allMethods =
                new Method[parentMethods.length + thisMethods.length];
	    System.arraycopy(parentMethods, 0, allMethods, 0,
                             parentMethods.length);
	    System.arraycopy(thisMethods, 0, allMethodsparentMethods.length,
                             thisMethods.length);
	    thisMethods = allMethods;
	}
	return thisMethods;
    }






    
Called by the server (via the service method) to allow a servlet to handle a OPTIONS request. The OPTIONS request determines which HTTP methods the server supports and returns an appropriate header. For example, if a servlet overrides doGet, this method returns the following header:

Allow: GET, HEAD, TRACE, OPTIONS

There's no need to override this method unless the servlet implements new HTTP methods, beyond those implemented by HTTP 1.1.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
resp the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the OPTIONS request
javax.servlet.ServletException if the request for the OPTIONS cannot be handled
         
    protected void doOptions(HttpServletRequest reqHttpServletResponse resp)
    {
	Method[] methods = getAllDeclaredMethods(this.getClass());
	boolean ALLOW_GET = false;
	boolean ALLOW_HEAD = false;
	boolean ALLOW_POST = false;
	boolean ALLOW_PUT = false;
	boolean ALLOW_DELETE = false;
	boolean ALLOW_TRACE = true;
	boolean ALLOW_OPTIONS = true;
	for (int i=0; i<methods.lengthi++) {
	    Method m = methods[i];
	    
	    if (m.getName().equals("doGet")) {
		ALLOW_GET = true;
		ALLOW_HEAD = true;
	    }
	    if (m.getName().equals("doPost")) 
		ALLOW_POST = true;
	    if (m.getName().equals("doPut"))
		ALLOW_PUT = true;
	    if (m.getName().equals("doDelete"))
		ALLOW_DELETE = true;
	    
	}
	String allow = null;
	if (ALLOW_GET)
	    allow=;
	if (ALLOW_HEAD)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	if (ALLOW_POST)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	if (ALLOW_PUT)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	if (ALLOW_DELETE)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	if (ALLOW_TRACE)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	if (ALLOW_OPTIONS)
	    if (allow==nullallow=;
	    else allow += ", " + ;
	resp.setHeader("Allow"allow);
    }
    
    
    
    
    
Called by the server (via the service method) to allow a servlet to handle a TRACE request. A TRACE returns the headers sent with the TRACE request to the client, so that they can be used in debugging. There's no need to override this method.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
resp the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the TRACE request
javax.servlet.ServletException if the request for the TRACE cannot be handled
    protected void doTrace(HttpServletRequest reqHttpServletResponse resp
        throws ServletExceptionIOException
    {
        int responseLength;
        String CRLF = "\r\n";
        StringBuilder buffer = new StringBuilder("TRACE ").append(req.getRequestURI())
            .append(" ").append(req.getProtocol());
        Enumeration<StringreqHeaderEnum = req.getHeaderNames();
        whilereqHeaderEnum.hasMoreElements() ) {
            String headerName = reqHeaderEnum.nextElement();
            buffer.append(CRLF).append(headerName).append(": ")
                .append(req.getHeader(headerName));
        }
        buffer.append(CRLF);
        responseLength = buffer.length();
        resp.setContentType("message/http");
        resp.setContentLength(responseLength);
        ServletOutputStream out = resp.getOutputStream();
        out.print(buffer.toString());	
    }		





    
Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class. This method is an HTTP-specific version of the javax.servlet.Servlet.service(javax.servlet.ServletRequest,javax.servlet.ServletResponse) method. There's no need to override this method.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
resp the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the HTTP request
javax.servlet.ServletException if the HTTP request cannot be handled
See also:
javax.servlet.Servlet.service(javax.servlet.ServletRequest,javax.servlet.ServletResponse)
    protected void service(HttpServletRequest reqHttpServletResponse resp)
    {
	String method = req.getMethod();
	if (method.equals()) {
	    long lastModified = getLastModified(req);
	    if (lastModified == -1) {
		// servlet doesn't support if-modified-since, no reason
		// to go through further expensive logic
		doGet(reqresp);
	    } else {
		long ifModifiedSince = req.getDateHeader();
		if (ifModifiedSince < lastModified) {
		    // If the servlet mod time is later, call doGet()
                    // Round down to the nearest second for a proper compare
                    // A ifModifiedSince of -1 will always be less
		    maybeSetLastModified(resplastModified);
		    doGet(reqresp);
else {
		}
	    }
else if (method.equals()) {
	    long lastModified = getLastModified(req);
	    maybeSetLastModified(resplastModified);
	    doHead(reqresp);
else if (method.equals()) {
	    doPost(reqresp);
	    
else if (method.equals()) {
	    doPut(reqresp);	
	    
else if (method.equals()) {
	    doDelete(reqresp);
	    
else if (method.equals()) {
	    doOptions(req,resp);
	    
else if (method.equals()) {
	    doTrace(req,resp);
	    
else {
	    //
	    // Note that this means NO servlet supports whatever
	    // method was requested, anywhere on this server.
	    //
	    String errMsg = .getString("http.method_not_implemented");
	    Object[] errArgs = new Object[1];
	    errArgs[0] = method;
	    errMsg = MessageFormat.format(errMsgerrArgs);
	    
	}
    }
    
    /*
     * Sets the Last-Modified entity header field, if it has not
     * already been set and if the value is meaningful.  Called before
     * doGet, to ensure that headers are set before response data is
     * written.  A subclass might have set this header already, so we
     * check.
     */
    private void maybeSetLastModified(HttpServletResponse resp,
				      long lastModified) {
	    return;
	if (lastModified >= 0)
	    resp.setDateHeader(lastModified);
    }
   
   
   
    
    
Dispatches client requests to the protected service method. There's no need to override this method.

Parameters:
req the HttpServletRequest object that contains the request the client made of the servlet
res the HttpServletResponse object that contains the response the servlet returns to the client
Throws:
java.io.IOException if an input or output error occurs while the servlet is handling the HTTP request
javax.servlet.ServletException if the HTTP request cannot be handled
See also:
javax.servlet.Servlet.service(javax.servlet.ServletRequest,javax.servlet.ServletResponse)
    public void service(ServletRequest reqServletResponse res)
    {
	try {
	    request = (HttpServletRequestreq;
	    response = (HttpServletResponseres;
catch (ClassCastException e) {
	    throw new ServletException("non-HTTP request or response");
	}
	service(requestresponse);
    }
/*
 * A response that includes no body, for use in (dumb) "HEAD" support.
 * This just swallows that body, counting the bytes in order to set
 * the content length appropriately.  All other methods delegate directly
 * to the wrapped HTTP Servlet Response object.
 */
// file private
    private static final ResourceBundle lStrings
        = ResourceBundle.getBundle("javax.servlet.http.LocalStrings");
    private NoBodyOutputStream		noBody;
    private PrintWriter			writer;
    private boolean			didSetContentLength;
    private boolean usingOutputStream;
    // file private
	super(r);
    }
    // file private
    void setContentLength() {
        if (!) {
            if ( != null) {
                .flush();
            }
            setContentLength(.getContentLength());
        }
    }
    public void setContentLength(int len) {
        super.setContentLength(len);
         = true;
    }
    public ServletOutputStream getOutputStream() throws IOException {
        if ( != null) {
            throw new IllegalStateException(
                .getString("err.ise.getOutputStream"));
        }
         = true;
        return ;
    }
        if () {
            throw new IllegalStateException(
                .getString("err.ise.getWriter"));
        }
        if ( == null) {
            OutputStreamWriter w = new OutputStreamWriter(
                getCharacterEncoding());
             = new PrintWriter(w);
        }
        return ;
    }
/*
 * Servlet output stream that gobbles up all its data.
 */
 
// file private
    private static final String LSTRING_FILE =
	"javax.servlet.http.LocalStrings";
    private static ResourceBundle lStrings =
	ResourceBundle.getBundle();
    private int		contentLength = 0;
    // file private
    NoBodyOutputStream() {}
    // file private
    int getContentLength() {
    }
    public void write(int b) {
    }
    public void write(byte buf[], int offsetint len)
    {
	if (len >= 0) {
	     += len;
else {
            // This should have thrown an IllegalArgumentException, but
            // changing this would break backwards compatibility
            throw new IOException(.getString("err.io.negativelength"));
	}
    }
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