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HttpURLConnection.javaAPI DocJava SE 6 API21180Tue Jun 10 00:25:40 BST 2008java.net

HttpURLConnection

public abstract class HttpURLConnection extends URLConnection
A URLConnection with support for HTTP-specific features. See the spec for details.

Each HttpURLConnection instance is used to make a single request but the underlying network connection to the HTTP server may be transparently shared by other instances. Calling the close() methods on the InputStream or OutputStream of an HttpURLConnection after a request may free network resources associated with this instance but has no effect on any shared persistent connection. Calling the disconnect() method may close the underlying socket if a persistent connection is otherwise idle at that time.

see
java.net.HttpURLConnection#disconnect()
since
JDK1.1

Fields Summary
protected String
method
The HTTP method (GET,POST,PUT,etc.).
protected int
chunkLength
The chunk-length when using chunked encoding streaming mode for output. A value of -1 means chunked encoding is disabled for output.
protected int
fixedContentLength
The fixed content-length when using fixed-length streaming mode. A value of -1 means fixed-length streaming mode is disabled for output.
private static final int
DEFAULT_CHUNK_SIZE
protected int
responseCode
An int representing the three digit HTTP Status-Code.
  • 1xx: Informational
  • 2xx: Success
  • 3xx: Redirection
  • 4xx: Client Error
  • 5xx: Server Error
protected String
responseMessage
The HTTP response message.
private static boolean
followRedirects
protected boolean
instanceFollowRedirects
If true, the protocol will automatically follow redirects. If false, the protocol will not automatically follow redirects.

This field is set by the setInstanceFollowRedirects method. Its value is returned by the getInstanceFollowRedirects method.

Its default value is based on the value of the static followRedirects at HttpURLConnection construction time.

private static final String[]
methods
public static final int
HTTP_OK
HTTP Status-Code 200: OK.
public static final int
HTTP_CREATED
HTTP Status-Code 201: Created.
public static final int
HTTP_ACCEPTED
HTTP Status-Code 202: Accepted.
public static final int
HTTP_NOT_AUTHORITATIVE
HTTP Status-Code 203: Non-Authoritative Information.
public static final int
HTTP_NO_CONTENT
HTTP Status-Code 204: No Content.
public static final int
HTTP_RESET
HTTP Status-Code 205: Reset Content.
public static final int
HTTP_PARTIAL
HTTP Status-Code 206: Partial Content.
public static final int
HTTP_MULT_CHOICE
HTTP Status-Code 300: Multiple Choices.
public static final int
HTTP_MOVED_PERM
HTTP Status-Code 301: Moved Permanently.
public static final int
HTTP_MOVED_TEMP
HTTP Status-Code 302: Temporary Redirect.
public static final int
HTTP_SEE_OTHER
HTTP Status-Code 303: See Other.
public static final int
HTTP_NOT_MODIFIED
HTTP Status-Code 304: Not Modified.
public static final int
HTTP_USE_PROXY
HTTP Status-Code 305: Use Proxy.
public static final int
HTTP_BAD_REQUEST
HTTP Status-Code 400: Bad Request.
public static final int
HTTP_UNAUTHORIZED
HTTP Status-Code 401: Unauthorized.
public static final int
HTTP_PAYMENT_REQUIRED
HTTP Status-Code 402: Payment Required.
public static final int
HTTP_FORBIDDEN
HTTP Status-Code 403: Forbidden.
public static final int
HTTP_NOT_FOUND
HTTP Status-Code 404: Not Found.
public static final int
HTTP_BAD_METHOD
HTTP Status-Code 405: Method Not Allowed.
public static final int
HTTP_NOT_ACCEPTABLE
HTTP Status-Code 406: Not Acceptable.
public static final int
HTTP_PROXY_AUTH
HTTP Status-Code 407: Proxy Authentication Required.
public static final int
HTTP_CLIENT_TIMEOUT
HTTP Status-Code 408: Request Time-Out.
public static final int
HTTP_CONFLICT
HTTP Status-Code 409: Conflict.
public static final int
HTTP_GONE
HTTP Status-Code 410: Gone.
public static final int
HTTP_LENGTH_REQUIRED
HTTP Status-Code 411: Length Required.
public static final int
HTTP_PRECON_FAILED
HTTP Status-Code 412: Precondition Failed.
public static final int
HTTP_ENTITY_TOO_LARGE
HTTP Status-Code 413: Request Entity Too Large.
public static final int
HTTP_REQ_TOO_LONG
HTTP Status-Code 414: Request-URI Too Large.
public static final int
HTTP_UNSUPPORTED_TYPE
HTTP Status-Code 415: Unsupported Media Type.
public static final int
HTTP_SERVER_ERROR
HTTP Status-Code 500: Internal Server Error.
public static final int
HTTP_INTERNAL_ERROR
HTTP Status-Code 500: Internal Server Error.
public static final int
HTTP_NOT_IMPLEMENTED
HTTP Status-Code 501: Not Implemented.
public static final int
HTTP_BAD_GATEWAY
HTTP Status-Code 502: Bad Gateway.
public static final int
HTTP_UNAVAILABLE
HTTP Status-Code 503: Service Unavailable.
public static final int
HTTP_GATEWAY_TIMEOUT
HTTP Status-Code 504: Gateway Timeout.
public static final int
HTTP_VERSION
HTTP Status-Code 505: HTTP Version Not Supported.
Constructors Summary
protected HttpURLConnection(URL u)
Constructor for the HttpURLConnection.

param
u the URL


                 
        
	super(u);
    
Methods Summary
public abstract voiddisconnect()
Indicates that other requests to the server are unlikely in the near future. Calling disconnect() should not imply that this HttpURLConnection instance can be reused for other requests.

public java.io.InputStreamgetErrorStream()
Returns the error stream if the connection failed but the server sent useful data nonetheless. The typical example is when an HTTP server responds with a 404, which will cause a FileNotFoundException to be thrown in connect, but the server sent an HTML help page with suggestions as to what to do.

This method will not cause a connection to be initiated. If the connection was not connected, or if the server did not have an error while connecting or if the server had an error but no error data was sent, this method will return null. This is the default.

return
an error stream if any, null if there have been no errors, the connection is not connected or the server sent no useful data.

	return null;
    
public static booleangetFollowRedirects()
Returns a boolean indicating whether or not HTTP redirects (3xx) should be automatically followed.

return
true if HTTP redirects should be automatically followed, false if not.
see
#setFollowRedirects(boolean)

	return followRedirects;
    
public java.lang.StringgetHeaderField(int n)
Returns the value for the nth header field. Some implementations may treat the 0th header field as special, i.e. as the status line returned by the HTTP server.

This method can be used in conjunction with the {@link #getHeaderFieldKey getHeaderFieldKey} method to iterate through all the headers in the message.

param
n an index, where n>=0.
return
the value of the nth header field, or null if the value does not exist.
see
java.net.HttpURLConnection#getHeaderFieldKey(int)

	return null;
    
public longgetHeaderFieldDate(java.lang.String name, long Default)

	String dateString = getHeaderField(name);
	try {
	    if (dateString.indexOf("GMT") == -1) {
	        dateString = dateString+" GMT";
	    }
	    return Date.parse(dateString);
	} catch (Exception e) {
	}
	return Default;
    
public java.lang.StringgetHeaderFieldKey(int n)
Returns the key for the nth header field. Some implementations may treat the 0th header field as special, i.e. as the status line returned by the HTTP server. In this case, {@link #getHeaderField(int) getHeaderField(0)} returns the status line, but getHeaderFieldKey(0) returns null.

param
n an index, where n >=0.
return
the key for the nth header field, or null if the key does not exist.


                                                                                          
         
	return null;
    
public booleangetInstanceFollowRedirects()
Returns the value of this HttpURLConnection's instanceFollowRedirects field.

return
the value of this HttpURLConnection's instanceFollowRedirects field.
see
java.net.HttpURLConnection#instanceFollowRedirects
see
#setInstanceFollowRedirects(boolean)
since
1.3

         return instanceFollowRedirects;
     
public java.security.PermissiongetPermission()

	int port = url.getPort();
	port = port < 0 ? 80 : port;
	String host = url.getHost() + ":" + port;
	Permission permission = new SocketPermission(host, "connect");
	return permission;
    
public java.lang.StringgetRequestMethod()
Get the request method.

return
the HTTP request method
see
#setRequestMethod(java.lang.String)

	return method;
    
public intgetResponseCode()
Gets the status code from an HTTP response message. For example, in the case of the following status lines:
HTTP/1.0 200 OK
HTTP/1.0 401 Unauthorized
It will return 200 and 401 respectively. Returns -1 if no code can be discerned from the response (i.e., the response is not valid HTTP).

throws
IOException if an error occurred connecting to the server.
return
the HTTP Status-Code, or -1

	/*
	 * We're got the response code already
	 */
	if (responseCode != -1) {
	    return responseCode;
	}

	/*
	 * Ensure that we have connected to the server. Record
	 * exception as we need to re-throw it if there isn't
	 * a status line.
	 */
	Exception exc = null;
	try {
            getInputStream();
	} catch (Exception e) {
	    exc = e;
	}

	/*
 	 * If we can't a status-line then re-throw any exception
	 * that getInputStream threw.
	 */
	String statusLine = getHeaderField(0);
	if (statusLine == null) {
	    if (exc != null) {
		if (exc instanceof RuntimeException)
                    throw (RuntimeException)exc;
                else
                    throw (IOException)exc;
	    }
	    return -1;
	}

	/*
	 * Examine the status-line - should be formatted as per
 	 * section 6.1 of RFC 2616 :-
	 *
	 * Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase
 	 *
	 * If status line can't be parsed return -1.
	 */
	if (statusLine.startsWith("HTTP/1.")) {
	    int codePos = statusLine.indexOf(' ");
	    if (codePos > 0) {

		int phrasePos = statusLine.indexOf(' ", codePos+1);
		if (phrasePos > 0 && phrasePos < statusLine.length()) {
		    responseMessage = statusLine.substring(phrasePos+1);
		}

		// deviation from RFC 2616 - don't reject status line
		// if SP Reason-Phrase is not included.
		if (phrasePos < 0) 
		    phrasePos = statusLine.length();

		try {
		    responseCode = Integer.parseInt
                            (statusLine.substring(codePos+1, phrasePos));	
		    return responseCode;
		} catch (NumberFormatException e) { }
	    }
	}
	return -1;
    
public java.lang.StringgetResponseMessage()
Gets the HTTP response message, if any, returned along with the response code from a server. From responses like:
HTTP/1.0 200 OK
HTTP/1.0 404 Not Found
Extracts the Strings "OK" and "Not Found" respectively. Returns null if none could be discerned from the responses (the result was not valid HTTP).

throws
IOException if an error occurred connecting to the server.
return
the HTTP response message, or null

	getResponseCode();
	return responseMessage;
    
public voidsetChunkedStreamingMode(int chunklen)
This method is used to enable streaming of a HTTP request body without internal buffering, when the content length is not known in advance. In this mode, chunked transfer encoding is used to send the request body. Note, not all HTTP servers support this mode.

When output streaming is enabled, authentication and redirection cannot be handled automatically. A HttpRetryException will be thrown when reading the response if authentication or redirection are required. This exception can be queried for the details of the error.

This method must be called before the URLConnection is connected.

param
chunklen The number of bytes to write in each chunk. If chunklen is less than or equal to zero, a default value will be used.
throws
IllegalStateException if URLConnection is already connected or if a different streaming mode is already enabled.
see
#setFixedLengthStreamingMode(int)
since
1.5


                                                                                                                 		           		            		                      
         
	if (connected) {
	    throw new IllegalStateException ("Can't set streaming mode: already connected");
	}
	if (fixedContentLength != -1) {
	    throw new IllegalStateException ("Fixed length streaming mode set");
	}
	chunkLength = chunklen <=0? DEFAULT_CHUNK_SIZE : chunklen;
    
public voidsetFixedLengthStreamingMode(int contentLength)
This method is used to enable streaming of a HTTP request body without internal buffering, when the content length is known in advance.

An exception will be thrown if the application attempts to write more data than the indicated content-length, or if the application closes the OutputStream before writing the indicated amount.

When output streaming is enabled, authentication and redirection cannot be handled automatically. A HttpRetryException will be thrown when reading the response if authentication or redirection are required. This exception can be queried for the details of the error.

This method must be called before the URLConnection is connected.

param
contentLength The number of bytes which will be written to the OutputStream.
throws
IllegalStateException if URLConnection is already connected or if a different streaming mode is already enabled.
throws
IllegalArgumentException if a content length less than zero is specified.
see
#setChunkedStreamingMode(int)
since
1.5

	if (connected) {
	    throw new IllegalStateException ("Already connected");
	}
	if (chunkLength != -1) {
	    throw new IllegalStateException ("Chunked encoding streaming mode set");
	}
	if (contentLength < 0) {
	    throw new IllegalArgumentException ("invalid content length");
	}
	fixedContentLength = contentLength;
    
public static voidsetFollowRedirects(boolean set)
Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this class. True by default. Applets cannot change this variable.

If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

param
set a boolean indicating whether or not to follow HTTP redirects.
exception
SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.
see
SecurityManager#checkSetFactory
see
#getFollowRedirects()

	SecurityManager sec = System.getSecurityManager();
	if (sec != null) {
	    // seems to be the best check here...
	    sec.checkSetFactory();
	}
	followRedirects = set;
    
public voidsetInstanceFollowRedirects(boolean followRedirects)
Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this HttpURLConnection instance.

The default value comes from followRedirects, which defaults to true.

param
followRedirects a boolean indicating whether or not to follow HTTP redirects.
see
java.net.HttpURLConnection#instanceFollowRedirects
see
#getInstanceFollowRedirects
since
1.3

 	instanceFollowRedirects = followRedirects;
     
public voidsetRequestMethod(java.lang.String method)
Set the method for the URL request, one of:
  • GET
  • POST
  • HEAD
  • OPTIONS
  • PUT
  • DELETE
  • TRACE
are legal, subject to protocol restrictions. The default method is GET.

param
method the HTTP method
exception
ProtocolException if the method cannot be reset or if the requested method isn't valid for HTTP.
see
#getRequestMethod()

	if (connected) {
	    throw new ProtocolException("Can't reset method: already connected");
	}
	// This restriction will prevent people from using this class to 
	// experiment w/ new HTTP methods using java.  But it should 
	// be placed for security - the request String could be
	// arbitrarily long.

	for (int i = 0; i < methods.length; i++) {
	    if (methods[i].equals(method)) {
		this.method = method;
		return;
	    }
	}
	throw new ProtocolException("Invalid HTTP method: " + method);
    
public abstract booleanusingProxy()
Indicates if the connection is going through a proxy.

return
a boolean indicating if the connection is using a proxy.