java.net
Class HttpURLConnection

java.lang.Object   
  java.net.URLConnection   
      java.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.

Since:

JDK1.1

See Also:

disconnect()

Field Summary

protected int	chunkLength The chunk-length when using chunked encoding streaming mode for output.
protected int	fixedContentLength The fixed content-length when using fixed-length streaming mode.
static int	HTTP_ACCEPTED HTTP Status-Code 202: Accepted.
static int	HTTP_BAD_GATEWAY HTTP Status-Code 502: Bad Gateway.
static int	HTTP_BAD_METHOD HTTP Status-Code 405: Method Not Allowed.
static int	HTTP_BAD_REQUEST HTTP Status-Code 400: Bad Request.
static int	HTTP_CLIENT_TIMEOUT HTTP Status-Code 408: Request Time-Out.
static int	HTTP_CONFLICT HTTP Status-Code 409: Conflict.
static int	HTTP_CREATED HTTP Status-Code 201: Created.
static int	HTTP_ENTITY_TOO_LARGE HTTP Status-Code 413: Request Entity Too Large.
static int	HTTP_FORBIDDEN HTTP Status-Code 403: Forbidden.
static int	HTTP_GATEWAY_TIMEOUT HTTP Status-Code 504: Gateway Timeout.
static int	HTTP_GONE HTTP Status-Code 410: Gone.
static int	HTTP_INTERNAL_ERROR HTTP Status-Code 500: Internal Server Error.
static int	HTTP_LENGTH_REQUIRED HTTP Status-Code 411: Length Required.
static int	HTTP_MOVED_PERM HTTP Status-Code 301: Moved Permanently.
static int	HTTP_MOVED_TEMP HTTP Status-Code 302: Temporary Redirect.
static int	HTTP_MULT_CHOICE HTTP Status-Code 300: Multiple Choices.
static int	HTTP_NO_CONTENT HTTP Status-Code 204: No Content.
static int	HTTP_NOT_ACCEPTABLE HTTP Status-Code 406: Not Acceptable.
static int	HTTP_NOT_AUTHORITATIVE HTTP Status-Code 203: Non-Authoritative Information.
static int	HTTP_NOT_FOUND HTTP Status-Code 404: Not Found.
static int	HTTP_NOT_IMPLEMENTED HTTP Status-Code 501: Not Implemented.
static int	HTTP_NOT_MODIFIED HTTP Status-Code 304: Not Modified.
static int	HTTP_OK HTTP Status-Code 200: OK.
static int	HTTP_PARTIAL HTTP Status-Code 206: Partial Content.
static int	HTTP_PAYMENT_REQUIRED HTTP Status-Code 402: Payment Required.
static int	HTTP_PRECON_FAILED HTTP Status-Code 412: Precondition Failed.
static int	HTTP_PROXY_AUTH HTTP Status-Code 407: Proxy Authentication Required.
static int	HTTP_REQ_TOO_LONG HTTP Status-Code 414: Request-URI Too Large.
static int	HTTP_RESET HTTP Status-Code 205: Reset Content.
static int	HTTP_SEE_OTHER HTTP Status-Code 303: See Other.
static int	HTTP_SERVER_ERROR Deprecated. it is misplaced and shouldn't have existed.
static int	HTTP_UNAUTHORIZED HTTP Status-Code 401: Unauthorized.
static int	HTTP_UNAVAILABLE HTTP Status-Code 503: Service Unavailable.
static int	HTTP_UNSUPPORTED_TYPE HTTP Status-Code 415: Unsupported Media Type.
static int	HTTP_USE_PROXY HTTP Status-Code 305: Use Proxy.
static int	HTTP_VERSION HTTP Status-Code 505: HTTP Version Not Supported.
protected boolean	instanceFollowRedirects If true, the protocol will automatically follow redirects.
protected String	method The HTTP method (GET,POST,PUT,etc.).
protected int	responseCode An int representing the three digit HTTP Status-Code.
protected String	responseMessage The HTTP response message.

Fields inherited from class java.net.URLConnection

allowUserInteraction , connected , doInput , doOutput , ifModifiedSince , url , useCaches

Constructor Summary

protected

HttpURLConnection (URL u) Constructor for the HttpURLConnection.

Method Summary

abstract void	disconnect () Indicates that other requests to the server are unlikely in the near future.
InputStream	getErrorStream () Returns the error stream if the connection failed but the server sent useful data nonetheless.
static boolean	getFollowRedirects () Returns a boolean indicating whether or not HTTP redirects (3xx) should be automatically followed.
String	getHeaderField (int n) Returns the value for the nth header field.
long	getHeaderFieldDate (String name, long Default) Returns the value of the named field parsed as date.
String	getHeaderFieldKey (int n) Returns the key for the nth header field.
boolean	getInstanceFollowRedirects () Returns the value of this HttpURLConnection's instanceFollowRedirects field.
Permission	getPermission () Returns a permission object representing the permission necessary to make the connection represented by this object.
String	getRequestMethod () Get the request method.
int	getResponseCode () Gets the status code from an HTTP response message.
String	getResponseMessage () Gets the HTTP response message, if any, returned along with the response code from a server.
void	setChunkedStreamingMode (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.
void	setFixedLengthStreamingMode (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.
static void	setFollowRedirects (boolean set) Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this class.
void	setInstanceFollowRedirects (boolean followRedirects) Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this HttpURLConnection instance.
void	setRequestMethod (String method) Set the method for the URL request, one of: GET POST HEAD OPTIONS PUT DELETE TRACE are legal, subject to protocol restrictions.
abstract boolean	usingProxy () Indicates if the connection is going through a proxy.

Methods inherited from class java.net.URLConnection

addRequestProperty , connect , getAllowUserInteraction , getConnectTimeout , getContent , getContent , getContentEncoding , getContentLength , getContentType , getDate , getDefaultAllowUserInteraction , getDefaultRequestProperty , getDefaultUseCaches , getDoInput , getDoOutput , getExpiration , getFileNameMap , getHeaderField , getHeaderFieldInt , getHeaderFields , getIfModifiedSince , getInputStream , getLastModified , getOutputStream , getReadTimeout , getRequestProperties , getRequestProperty , getURL , getUseCaches , guessContentTypeFromName , guessContentTypeFromStream , setAllowUserInteraction , setConnectTimeout , setContentHandlerFactory , setDefaultAllowUserInteraction , setDefaultRequestProperty , setDefaultUseCaches , setDoInput , setDoOutput , setFileNameMap , setIfModifiedSince , setReadTimeout , setRequestProperty , setUseCaches , toString

Methods inherited from class java.lang.Object

clone , equals , finalize , getClass , hashCode , notify , notifyAll , wait , wait , wait

Field Detail

method

protected String    method

The HTTP method (GET,POST,PUT,etc.).

chunkLength

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.

fixedContentLength

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.

responseCode

protected int responseCode

An int representing the three digit HTTP Status-Code.

• 1xx: Informational
• 2xx: Success
• 3xx: Redirection
• 4xx: Client Error
• 5xx: Server Error

responseMessage

protected String    responseMessage

The HTTP response message.

instanceFollowRedirects

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.

See Also:

setInstanceFollowRedirects(boolean) , getInstanceFollowRedirects() , setFollowRedirects(boolean)

HTTP_OK

public static final int HTTP_OK

HTTP Status-Code 200: OK.

See Also:

Constant Field Values

HTTP_CREATED

public static final int HTTP_CREATED

HTTP Status-Code 201: Created.

See Also:

Constant Field Values

HTTP_ACCEPTED

public static final int HTTP_ACCEPTED

HTTP Status-Code 202: Accepted.

See Also:

Constant Field Values

HTTP_NOT_AUTHORITATIVE

public static final int HTTP_NOT_AUTHORITATIVE

HTTP Status-Code 203: Non-Authoritative Information.

See Also:

Constant Field Values

HTTP_NO_CONTENT

public static final int HTTP_NO_CONTENT

HTTP Status-Code 204: No Content.

See Also:

Constant Field Values

HTTP_RESET

public static final int HTTP_RESET

HTTP Status-Code 205: Reset Content.

See Also:

Constant Field Values

HTTP_PARTIAL

public static final int HTTP_PARTIAL

HTTP Status-Code 206: Partial Content.

See Also:

Constant Field Values

HTTP_MULT_CHOICE

public static final int HTTP_MULT_CHOICE

HTTP Status-Code 300: Multiple Choices.

See Also:

Constant Field Values

HTTP_MOVED_PERM

public static final int HTTP_MOVED_PERM

HTTP Status-Code 301: Moved Permanently.

See Also:

Constant Field Values

HTTP_MOVED_TEMP

public static final int HTTP_MOVED_TEMP

HTTP Status-Code 302: Temporary Redirect.

See Also:

Constant Field Values

HTTP_SEE_OTHER

public static final int HTTP_SEE_OTHER

HTTP Status-Code 303: See Other.

See Also:

Constant Field Values

HTTP_NOT_MODIFIED

public static final int HTTP_NOT_MODIFIED

HTTP Status-Code 304: Not Modified.

See Also:

Constant Field Values

HTTP_USE_PROXY

public static final int HTTP_USE_PROXY

HTTP Status-Code 305: Use Proxy.

See Also:

Constant Field Values

HTTP_BAD_REQUEST

public static final int HTTP_BAD_REQUEST

HTTP Status-Code 400: Bad Request.

See Also:

Constant Field Values

HTTP_UNAUTHORIZED

public static final int HTTP_UNAUTHORIZED

HTTP Status-Code 401: Unauthorized.

See Also:

Constant Field Values

HTTP_PAYMENT_REQUIRED

public static final int HTTP_PAYMENT_REQUIRED

HTTP Status-Code 402: Payment Required.

See Also:

Constant Field Values

HTTP_FORBIDDEN

public static final int HTTP_FORBIDDEN

HTTP Status-Code 403: Forbidden.

See Also:

Constant Field Values

HTTP_NOT_FOUND

public static final int HTTP_NOT_FOUND

HTTP Status-Code 404: Not Found.

See Also:

Constant Field Values

HTTP_BAD_METHOD

public static final int HTTP_BAD_METHOD

HTTP Status-Code 405: Method Not Allowed.

See Also:

Constant Field Values

HTTP_NOT_ACCEPTABLE

public static final int HTTP_NOT_ACCEPTABLE

HTTP Status-Code 406: Not Acceptable.

See Also:

Constant Field Values

HTTP_PROXY_AUTH

public static final int HTTP_PROXY_AUTH

HTTP Status-Code 407: Proxy Authentication Required.

See Also:

Constant Field Values

HTTP_CLIENT_TIMEOUT

public static final int HTTP_CLIENT_TIMEOUT

HTTP Status-Code 408: Request Time-Out.

See Also:

Constant Field Values

HTTP_CONFLICT

public static final int HTTP_CONFLICT

HTTP Status-Code 409: Conflict.

See Also:

Constant Field Values

HTTP_GONE

public static final int HTTP_GONE

HTTP Status-Code 410: Gone.

See Also:

Constant Field Values

HTTP_LENGTH_REQUIRED

public static final int HTTP_LENGTH_REQUIRED

HTTP Status-Code 411: Length Required.

See Also:

Constant Field Values

HTTP_PRECON_FAILED

public static final int HTTP_PRECON_FAILED

HTTP Status-Code 412: Precondition Failed.

See Also:

Constant Field Values

HTTP_ENTITY_TOO_LARGE

public static final int HTTP_ENTITY_TOO_LARGE

HTTP Status-Code 413: Request Entity Too Large.

See Also:

Constant Field Values

HTTP_REQ_TOO_LONG

public static final int HTTP_REQ_TOO_LONG

HTTP Status-Code 414: Request-URI Too Large.

See Also:

Constant Field Values

HTTP_UNSUPPORTED_TYPE

public static final int HTTP_UNSUPPORTED_TYPE

HTTP Status-Code 415: Unsupported Media Type.

See Also:

Constant Field Values

HTTP_SERVER_ERROR

@Deprecated
public static final int HTTP_SERVER_ERROR

Deprecated. it is misplaced and shouldn't have existed.

HTTP Status-Code 500: Internal Server Error.

See Also:

Constant Field Values

HTTP_INTERNAL_ERROR

public static final int HTTP_INTERNAL_ERROR

HTTP Status-Code 500: Internal Server Error.

See Also:

Constant Field Values

HTTP_NOT_IMPLEMENTED

public static final int HTTP_NOT_IMPLEMENTED

HTTP Status-Code 501: Not Implemented.

See Also:

Constant Field Values

HTTP_BAD_GATEWAY

public static final int HTTP_BAD_GATEWAY

HTTP Status-Code 502: Bad Gateway.

See Also:

Constant Field Values

HTTP_UNAVAILABLE

public static final int HTTP_UNAVAILABLE

HTTP Status-Code 503: Service Unavailable.

See Also:

Constant Field Values

HTTP_GATEWAY_TIMEOUT

public static final int HTTP_GATEWAY_TIMEOUT

HTTP Status-Code 504: Gateway Timeout.

See Also:

Constant Field Values

HTTP_VERSION

public static final int HTTP_VERSION

HTTP Status-Code 505: HTTP Version Not Supported.

See Also:

Constant Field Values

Constructor Detail

HttpURLConnection

protected HttpURLConnection(URL    u)

Constructor for the HttpURLConnection.

Parameters:

u - the URL

Method Detail

getHeaderFieldKey

public String    getHeaderFieldKey(int n)

Returns the key for the n^th header field. Some implementations may treat the 0^th header field as special, i.e. as the status line returned by the HTTP server. In this case, getHeaderField(0) returns the status line, but getHeaderFieldKey(0) returns null.

Overrides:

getHeaderFieldKey in class URLConnection

Parameters:

n - an index, where n >=0.

Returns:

the key for the n^th header field, or null if the key does not exist.

setFixedLengthStreamingMode

public void setFixedLengthStreamingMode(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.

Parameters:

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.

IllegalArgumentException - if a content length less than zero is specified.

See Also:

setChunkedStreamingMode(int)

setChunkedStreamingMode

public void setChunkedStreamingMode(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.

Parameters:

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 Also:

setFixedLengthStreamingMode(int)

getHeaderField

public String    getHeaderField(int n)

Returns the value for the n^th header field. Some implementations may treat the 0^th header field as special, i.e. as the status line returned by the HTTP server.

This method can be used in conjunction with the getHeaderFieldKey method to iterate through all the headers in the message.

Overrides:

getHeaderField in class URLConnection

Parameters:

n - an index, where n>=0.

Returns:

the value of the n^th header field, or null if the value does not exist.

See Also:

getHeaderFieldKey(int)

setFollowRedirects

public static void setFollowRedirects(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.

Parameters:

set - a boolean indicating whether or not to follow HTTP redirects.

Throws:

SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.

See Also:

SecurityManager.checkSetFactory() , getFollowRedirects()

getFollowRedirects

public static boolean getFollowRedirects()

Returns a boolean indicating whether or not HTTP redirects (3xx) should be automatically followed.

Returns:

true if HTTP redirects should be automatically followed, false if not.

See Also:

setFollowRedirects(boolean)

setInstanceFollowRedirects

public void setInstanceFollowRedirects(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.

Parameters:

followRedirects - a boolean indicating whether or not to follow HTTP redirects.

See Also:

instanceFollowRedirects , getInstanceFollowRedirects()

getInstanceFollowRedirects

public boolean getInstanceFollowRedirects()

Returns the value of this HttpURLConnection's instanceFollowRedirects field.

Returns:

the value of this HttpURLConnection's instanceFollowRedirects field.

See Also:

instanceFollowRedirects , setInstanceFollowRedirects(boolean)

setRequestMethod

public void setRequestMethod(String    method)
                      throws ProtocolException   

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.

Parameters:

method - the HTTP method

Throws:

ProtocolException - if the method cannot be reset or if the requested method isn't valid for HTTP.

See Also:

getRequestMethod()

getRequestMethod

public String    getRequestMethod()

Get the request method.

Returns:

the HTTP request method

See Also:

setRequestMethod(java.lang.String)

getResponseCode

public int getResponseCode()
                    throws IOException   

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).

Returns:

the HTTP Status-Code, or -1

Throws:

IOException - if an error occurred connecting to the server.

getResponseMessage

public String    getResponseMessage()
                          throws IOException   

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).

Returns:

the HTTP response message, or null

Throws:

IOException - if an error occurred connecting to the server.

getHeaderFieldDate

public long getHeaderFieldDate(String    name,
                               long Default)

Description copied from class: URLConnection

Returns the value of the named field parsed as date. The result is the number of milliseconds since January 1, 1970 GMT represented by the named field.

This form of getHeaderField exists because some connection types (e.g., http-ng) have pre-parsed headers. Classes for that connection type can override this method and short-circuit the parsing.

Overrides:

getHeaderFieldDate in class URLConnection

Parameters:

name - the name of the header field.

Default - a default value.

Returns:

the value of the field, parsed as a date. The value of the Default argument is returned if the field is missing or malformed.

disconnect

public abstract void disconnect()

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.

usingProxy

public abstract boolean usingProxy()

Indicates if the connection is going through a proxy.

Returns:

a boolean indicating if the connection is using a proxy.

getPermission

public Permission    getPermission()
                         throws IOException   

Description copied from class: URLConnection

Returns a permission object representing the permission necessary to make the connection represented by this object. This method returns null if no permission is required to make the connection. By default, this method returns java.security.AllPermission. Subclasses should override this method and return the permission that best represents the permission required to make a a connection to the URL. For example, a URLConnection representing a file: URL would return a java.io.FilePermission object.

The permission returned may dependent upon the state of the connection. For example, the permission before connecting may be different from that after connecting. For example, an HTTP sever, say foo.com, may redirect the connection to a different host, say bar.com. Before connecting the permission returned by the connection will represent the permission needed to connect to foo.com, while the permission returned after connecting will be to bar.com.

Permissions are generally used for two purposes: to protect caches of objects obtained through URLConnections, and to check the right of a recipient to learn about a particular URL. In the first case, the permission should be obtained after the object has been obtained. For example, in an HTTP connection, this will represent the permission to connect to the host from which the data was ultimately fetched. In the second case, the permission should be obtained and tested before connecting.

Overrides:

getPermission in class URLConnection

Returns:

the permission object representing the permission necessary to make the connection represented by this URLConnection.

Throws:

IOException - if the computation of the permission requires network or file I/O and an exception occurs while computing it.

getErrorStream

public InputStream    getErrorStream()

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.

Returns:

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