public abstract class HttpURLConnection extends URLConnection
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.
The HTTP protocol handler has a few settings that can be accessed through System Properties. This covers Proxy settings as well as various other settings.
Security permissions
 If a security manager is installed, and if a method is called which results in an attempt to open a connection, the
 caller must possess a "connect" SocketPermission to the host/port combination of the destination URL
 
If automatic redirection is enabled, and this request is redirected to another destination, then the caller must also have permission to connect to the redirected host/URL.
disconnect()| Modifier and Type | Field and Description | 
|---|---|
| protected int | chunkLengthThe chunk-length when using chunked encoding streaming mode for output. | 
| protected int | fixedContentLengthThe fixed content-length when using fixed-length streaming mode. | 
| protected long | fixedContentLengthLongThe fixed content-length when using fixed-length streaming mode. | 
| static int | HTTP_ACCEPTEDHTTP Status-Code 202: Accepted. | 
| static int | HTTP_BAD_GATEWAYHTTP Status-Code 502: Bad Gateway. | 
| static int | HTTP_BAD_METHODHTTP Status-Code 405: Method Not Allowed. | 
| static int | HTTP_BAD_REQUESTHTTP Status-Code 400: Bad Request. | 
| static int | HTTP_CLIENT_TIMEOUTHTTP Status-Code 408: Request Time-Out. | 
| static int | HTTP_CONFLICTHTTP Status-Code 409: Conflict. | 
| static int | HTTP_CREATEDHTTP Status-Code 201: Created. | 
| static int | HTTP_ENTITY_TOO_LARGEHTTP Status-Code 413: Request Entity Too Large. | 
| static int | HTTP_FORBIDDENHTTP Status-Code 403: Forbidden. | 
| static int | HTTP_GATEWAY_TIMEOUTHTTP Status-Code 504: Gateway Timeout. | 
| static int | HTTP_GONEHTTP Status-Code 410: Gone. | 
| static int | HTTP_INTERNAL_ERRORHTTP Status-Code 500: Internal Server Error. | 
| static int | HTTP_LENGTH_REQUIREDHTTP Status-Code 411: Length Required. | 
| static int | HTTP_MOVED_PERMHTTP Status-Code 301: Moved Permanently. | 
| static int | HTTP_MOVED_TEMPHTTP Status-Code 302: Temporary Redirect. | 
| static int | HTTP_MULT_CHOICEHTTP Status-Code 300: Multiple Choices. | 
| static int | HTTP_NO_CONTENTHTTP Status-Code 204: No Content. | 
| static int | HTTP_NOT_ACCEPTABLEHTTP Status-Code 406: Not Acceptable. | 
| static int | HTTP_NOT_AUTHORITATIVEHTTP Status-Code 203: Non-Authoritative Information. | 
| static int | HTTP_NOT_FOUNDHTTP Status-Code 404: Not Found. | 
| static int | HTTP_NOT_IMPLEMENTEDHTTP Status-Code 501: Not Implemented. | 
| static int | HTTP_NOT_MODIFIEDHTTP Status-Code 304: Not Modified. | 
| static int | HTTP_OKHTTP Status-Code 200: OK. | 
| static int | HTTP_PARTIALHTTP Status-Code 206: Partial Content. | 
| static int | HTTP_PAYMENT_REQUIREDHTTP Status-Code 402: Payment Required. | 
| static int | HTTP_PRECON_FAILEDHTTP Status-Code 412: Precondition Failed. | 
| static int | HTTP_PROXY_AUTHHTTP Status-Code 407: Proxy Authentication Required. | 
| static int | HTTP_REQ_TOO_LONGHTTP Status-Code 414: Request-URI Too Large. | 
| static int | HTTP_RESETHTTP Status-Code 205: Reset Content. | 
| static int | HTTP_SEE_OTHERHTTP Status-Code 303: See Other. | 
| static int | HTTP_UNAUTHORIZEDHTTP Status-Code 401: Unauthorized. | 
| static int | HTTP_UNAVAILABLEHTTP Status-Code 503: Service Unavailable. | 
| static int | HTTP_UNSUPPORTED_TYPEHTTP Status-Code 415: Unsupported Media Type. | 
| static int | HTTP_USE_PROXYHTTP Status-Code 305: Use Proxy. | 
| static int | HTTP_VERSIONHTTP Status-Code 505: HTTP Version Not Supported. | 
| protected boolean | instanceFollowRedirectsIf  true, the protocol will automatically follow redirects. | 
| protected String | methodThe HTTP method (GET,POST,PUT,etc.). | 
| protected int | responseCodeAn  intrepresenting the three digit HTTP Status-Code. | 
| protected String | responseMessageThe HTTP response message. | 
allowUserInteraction, connected, doInput, doOutput, url, useCaches| Modifier | Constructor and Description | 
|---|---|
| protected  | HttpURLConnection(URL u)Constructor for the HttpURLConnection. | 
| Modifier and Type | Method and Description | 
|---|---|
| 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  booleanindicating whether or not HTTP redirects (3xx) should be automatically followed. | 
| String | getHeaderField(int n)Returns the value for the  nth header field. | 
| String | getHeaderFieldKey(int n)Returns the key for the  nth header field. | 
| boolean | getInstanceFollowRedirects()Returns the value of this  HttpURLConnection'sinstanceFollowRedirectsfield. | 
| Permission | getPermission()Returns a  SocketPermissionobject representing the permission necessary to connect to the destination
 host and port. | 
| 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. | 
| void | setFixedLengthStreamingMode(long 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
  HttpURLConnectioninstance. | 
| 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. | 
addRequestProperty, connect, getAllowUserInteraction, getConnectTimeout, getContent, getContent, getContentEncoding, getContentLength, getContentLengthLong, getContentType, getDefaultAllowUserInteraction, getDefaultUseCaches, getDoInput, getDoOutput, getHeaderField, getHeaderFieldInt, getHeaderFieldLong, getHeaderFields, getInputStream, getOutputStream, getReadTimeout, getRequestProperties, getRequestProperty, getURL, getUseCaches, setAllowUserInteraction, setConnectTimeout, setContentHandlerFactory, setDefaultAllowUserInteraction, setDefaultUseCaches, setDoInput, setDoOutput, setReadTimeout, setRequestProperty, setUseCaches, toStringprotected int chunkLength
-1 means chunked
 encoding is disabled for output.protected int fixedContentLength
-1 means fixed-length
 streaming mode is disabled for output.
 
 NOTE: fixedContentLengthLong is recommended instead of this field, as it allows larger content
 lengths to be set.
protected long fixedContentLengthLong
-1 means fixed-length
 streaming mode is disabled for output.public static final int HTTP_ACCEPTED
public static final int HTTP_BAD_GATEWAY
public static final int HTTP_BAD_METHOD
public static final int HTTP_BAD_REQUEST
public static final int HTTP_CLIENT_TIMEOUT
public static final int HTTP_CONFLICT
public static final int HTTP_CREATED
public static final int HTTP_ENTITY_TOO_LARGE
public static final int HTTP_FORBIDDEN
public static final int HTTP_GATEWAY_TIMEOUT
public static final int HTTP_GONE
public static final int HTTP_INTERNAL_ERROR
public static final int HTTP_LENGTH_REQUIRED
public static final int HTTP_MOVED_PERM
public static final int HTTP_MOVED_TEMP
public static final int HTTP_MULT_CHOICE
public static final int HTTP_NO_CONTENT
public static final int HTTP_NOT_ACCEPTABLE
public static final int HTTP_NOT_AUTHORITATIVE
public static final int HTTP_NOT_FOUND
public static final int HTTP_NOT_IMPLEMENTED
public static final int HTTP_NOT_MODIFIED
public static final int HTTP_OK
public static final int HTTP_PARTIAL
public static final int HTTP_PAYMENT_REQUIRED
public static final int HTTP_PRECON_FAILED
public static final int HTTP_PROXY_AUTH
public static final int HTTP_REQ_TOO_LONG
public static final int HTTP_RESET
public static final int HTTP_SEE_OTHER
public static final int HTTP_UNAUTHORIZED
public static final int HTTP_UNAVAILABLE
public static final int HTTP_UNSUPPORTED_TYPE
public static final int HTTP_USE_PROXY
public static final int HTTP_VERSION
protected boolean instanceFollowRedirects
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.
protected String method
protected int responseCode
int representing the three digit HTTP Status-Code.
 protected HttpURLConnection(URL u)
u - the URLpublic abstract void disconnect()
@Nullable public InputStream getErrorStream()
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.
public static boolean getFollowRedirects()
boolean indicating whether or not HTTP redirects (3xx) should be automatically followed.true if HTTP redirects should be automatically followed, false if not.setFollowRedirects(boolean)@Nullable public String getHeaderField(int n)
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 getHeaderFieldKey method to iterate
 through all the headers in the message.
getHeaderField in class URLConnectionn - an index, where n>=0.nth header field, or null if the value does not exist.getHeaderFieldKey(int)@Nullable public String getHeaderFieldKey(int n)
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, getHeaderField(0) returns the status line, but getHeaderFieldKey(0)
 returns null.getHeaderFieldKey in class URLConnectionn - an index, where n >=0.nth header field, or null if the key does not exist.public boolean getInstanceFollowRedirects()
HttpURLConnection's instanceFollowRedirects field.HttpURLConnection's instanceFollowRedirects field.instanceFollowRedirects, 
setInstanceFollowRedirects(boolean)public Permission getPermission() throws IOException
SocketPermission object representing the permission necessary to connect to the destination
 host and port.SocketPermission object representing the permission necessary to connect to the destination
         host and port.IOException - if an error occurs while computing the permission.public String getRequestMethod()
setRequestMethod(java.lang.String)public int getResponseCode()
                    throws IOException
HTTP/1.0 200 OK HTTP/1.0 401 UnauthorizedIt 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).
IOException - if an error occurred connecting to the server.@Nullable public String getResponseMessage() throws IOException
HTTP/1.0 200 OK HTTP/1.0 404 Not FoundExtracts the Strings "OK" and "Not Found" respectively. Returns null if none could be discerned from the responses (the result was not valid HTTP).
nullIOException - if an error occurred connecting to the server.public void setChunkedStreamingMode(int chunklen)
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.
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.IllegalStateException - if URLConnection is already connected or if a different streaming mode is already enabled.setFixedLengthStreamingMode(int)public void setFixedLengthStreamingMode(int contentLength)
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.
 NOTE: setFixedLengthStreamingMode(long) is recommended instead of this method as it allows larger
 content lengths to be set.
contentLength - The number of bytes which will be written to the OutputStream.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.setChunkedStreamingMode(int)public void setFixedLengthStreamingMode(long contentLength)
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.
 The content length set by invoking this method takes precedence over any value set by
 setFixedLengthStreamingMode(int).
contentLength - The number of bytes which will be written to the OutputStream.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.public static void setFollowRedirects(boolean set)
 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.
set - a boolean indicating whether or not to follow HTTP redirects.SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.getFollowRedirects()public void setInstanceFollowRedirects(boolean followRedirects)
HttpURLConnection instance.
 The default value comes from followRedirects, which defaults to true.
followRedirects - a boolean indicating whether or not to follow HTTP redirects.instanceFollowRedirects, 
getInstanceFollowRedirects()public void setRequestMethod(String method) throws ProtocolException
method - the HTTP methodProtocolException - if the method cannot be reset or if the requested method isn't valid for HTTP.SecurityException - if a security manager is set and the method is "TRACE", but the "allowHttpTrace" NetPermission is
                not granted.getRequestMethod()public abstract boolean usingProxy()