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Java Standard Edition (SE)

HttpURLConnection


compact1, compact2, compact3
java.net

Class HttpURLConnection

  • Direct Known Subclasses:
    HttpsURLConnection


    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:-

    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.

    Since:
    JDK1.1
    See Also:
    disconnect()
    • 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.
        Since:
        1.5
      • 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.

        NOTE: fixedContentLengthLong is recommended instead of this field, as it allows larger content lengths to be set.

        Since:
        1.5
      • fixedContentLengthLong

        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.
        Since:
        1.7
      • 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_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 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.
        Overrides:
        getHeaderFieldKey in class URLConnection
        Parameters:
        n - an index, where n >=0.
        Returns:
        the key for the nth 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.

        NOTE: setFixedLengthStreamingMode(long) is recommended instead of this method as it allows larger content lengths to be set.

        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.
        Since:
        1.5
        See Also:
        setChunkedStreamingMode(int)
      • setFixedLengthStreamingMode

        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).

        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.
        Since:
        1.7
      • 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.
        Since:
        1.5
        See Also:
        setFixedLengthStreamingMode(int)
      • getHeaderField

        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.

        Overrides:
        getHeaderField in class URLConnection
        Parameters:
        n - an index, where n>=0.
        Returns:
        the value of the nth 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.
        Since:
        1.3
        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.
        Since:
        1.3
        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.
        SecurityException - if a security manager is set and the method is "TRACE", but the "allowHttpTrace" NetPermission is not granted.
        See Also:
        getRequestMethod()
      • 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
        Returns a SocketPermission object representing the permission necessary to connect to the destination host and port.
        Overrides:
        getPermission in class URLConnection
        Returns:
        a SocketPermission object representing the permission necessary to connect to the destination host and port.
        Throws:
        IOException - if an error occurs while computing the permission.
      • 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.


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