HttpURLConnection

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## java.net
Class HttpURLConnection

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

Since:
  JDK1.1
See Also:
  `disconnect()`

Field Summary
`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_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.

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 `n`th 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 `n`th 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.
`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, getContent, getContent, getContentEncoding, getContentLength, getContentType, getDate, getDefaultAllowUserInteraction, getDefaultUseCaches, getDoInput, getDoOutput, getExpiration, getFileNameMap, getHeaderField, getHeaderFieldInt, getHeaderFields, getIfModifiedSince, getInputStream, getLastModified, getOutputStream, getRequestProperties, getRequestProperty, getURL, getUseCaches, guessContentTypeFromName, guessContentTypeFromStream, setAllowUserInteraction, setContentHandlerFactory, setDefaultAllowUserInteraction, setDefaultUseCaches, setDoInput, setDoOutput, setFileNameMap, setIfModifiedSince, setRequestProperty, setUseCaches, toString`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### 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_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

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.

### 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.

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