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.
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 either:-
SocketPermission to the host/port combination of the destination URL orURLPermission that permits this request.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()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.
NOTE: fixedContentLengthLong is recommended instead of this field, as it allows larger content lengths to be set.
protected long fixedContentLengthLong
The fixed content-length when using fixed-length streaming mode. A value of -1 means fixed-length streaming mode is disabled for output.
protected int responseCode
An int representing the three digit HTTP Status-Code.
protected String responseMessage
The HTTP response message.
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.
setInstanceFollowRedirects(boolean), getInstanceFollowRedirects(), setFollowRedirects(boolean)
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.
@Deprecated public static final int HTTP_SERVER_ERROR
Deprecated. it is misplaced and shouldn't have existed.
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.
protected HttpURLConnection(URL u)
Constructor for the HttpURLConnection.
u - the URLpublic String getHeaderFieldKey(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, getHeaderField(0) returns the status line, but getHeaderFieldKey(0) returns null.
getHeaderFieldKey in class URLConnection
n - an index, where n >=0.nth header field, or null if the key does not exist.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.
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)
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.
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 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.
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 String getHeaderField(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 getHeaderFieldKey method to iterate through all the headers in the message.
getHeaderField in class URLConnection
n - an index, where n>=0.nth header field, or null if the value does not exist.getHeaderFieldKey(int)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.
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.SecurityManager.checkSetFactory(), getFollowRedirects()
public static boolean getFollowRedirects()
Returns a 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)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.
followRedirects - a boolean indicating whether or not to follow HTTP redirects.instanceFollowRedirects, getInstanceFollowRedirects()
public boolean getInstanceFollowRedirects()
Returns the value of this HttpURLConnection's instanceFollowRedirects field.
HttpURLConnection's instanceFollowRedirects field.instanceFollowRedirects, setInstanceFollowRedirects(boolean)
public void setRequestMethod(String method) throws ProtocolException
Set the method for the URL request, one of:
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 String getRequestMethod()
Get the request method.
setRequestMethod(java.lang.String)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 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.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 FoundExtracts the Strings "OK" and "Not Found" respectively. Returns null if none could be discerned from the responses (the result was not valid HTTP).
null
IOException - if an error occurred connecting to the server.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.
getHeaderFieldDate in class URLConnection
name - the name of the header field.Default - a default value.Default argument is returned if the field is missing or malformed.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.
public abstract boolean usingProxy()
Indicates if the connection is going through a proxy.
public Permission getPermission() throws IOException
Returns a SocketPermission object representing the permission necessary to connect to the destination host and port.
getPermission in class URLConnection
SocketPermission object representing the permission necessary to connect to the destination host and port.IOException - if an error occurs while computing the permission.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.
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