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Class HttpURLConnection

java.lang.Objectjava.net.URLConnectionjava.net.HttpURLConnection

Direct Known Subclasses:

HttpsURLConnection

public abstract classHttpURLConnection
extendsURLConnection

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()

method

protectedStringmethod

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

chunkLength

protected intchunkLength

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 intfixedContentLength

The fixed content-length when using fixed-length streaming mode. A value of-1 means fixed-length streaming mode is disabled for output.

Since:

1.5

responseCode

protected intresponseCode

Anint representing the three digit HTTP Status-Code.

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

responseMessage

protectedStringresponseMessage

The HTTP response message.

instanceFollowRedirects

protected booleaninstanceFollowRedirects

Iftrue, the protocol will automatically follow redirects. Iffalse, the protocol will not automatically follow redirects.

This field is set by thesetInstanceFollowRedirects method. Its value is returned by thegetInstanceFollowRedirects 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 intHTTP_OK

HTTP Status-Code 200: OK.

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HTTP_CREATED

public static final intHTTP_CREATED

HTTP Status-Code 201: Created.

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HTTP_ACCEPTED

public static final intHTTP_ACCEPTED

HTTP Status-Code 202: Accepted.

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HTTP_NOT_AUTHORITATIVE

public static final intHTTP_NOT_AUTHORITATIVE

HTTP Status-Code 203: Non-Authoritative Information.

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HTTP_NO_CONTENT

public static final intHTTP_NO_CONTENT

HTTP Status-Code 204: No Content.

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HTTP_RESET

public static final intHTTP_RESET

HTTP Status-Code 205: Reset Content.

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HTTP_PARTIAL

public static final intHTTP_PARTIAL

HTTP Status-Code 206: Partial Content.

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HTTP_MULT_CHOICE

public static final intHTTP_MULT_CHOICE

HTTP Status-Code 300: Multiple Choices.

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HTTP_MOVED_PERM

public static final intHTTP_MOVED_PERM

HTTP Status-Code 301: Moved Permanently.

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HTTP_MOVED_TEMP

public static final intHTTP_MOVED_TEMP

HTTP Status-Code 302: Temporary Redirect.

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HTTP_SEE_OTHER

public static final intHTTP_SEE_OTHER

HTTP Status-Code 303: See Other.

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HTTP_NOT_MODIFIED

public static final intHTTP_NOT_MODIFIED

HTTP Status-Code 304: Not Modified.

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HTTP_USE_PROXY

public static final intHTTP_USE_PROXY

HTTP Status-Code 305: Use Proxy.

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HTTP_BAD_REQUEST

public static final intHTTP_BAD_REQUEST

HTTP Status-Code 400: Bad Request.

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HTTP_UNAUTHORIZED

public static final intHTTP_UNAUTHORIZED

HTTP Status-Code 401: Unauthorized.

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HTTP_PAYMENT_REQUIRED

public static final intHTTP_PAYMENT_REQUIRED

HTTP Status-Code 402: Payment Required.

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HTTP_FORBIDDEN

public static final intHTTP_FORBIDDEN

HTTP Status-Code 403: Forbidden.

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HTTP_NOT_FOUND

public static final intHTTP_NOT_FOUND

HTTP Status-Code 404: Not Found.

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HTTP_BAD_METHOD

public static final intHTTP_BAD_METHOD

HTTP Status-Code 405: Method Not Allowed.

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HTTP_NOT_ACCEPTABLE

public static final intHTTP_NOT_ACCEPTABLE

HTTP Status-Code 406: Not Acceptable.

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HTTP_PROXY_AUTH

public static final intHTTP_PROXY_AUTH

HTTP Status-Code 407: Proxy Authentication Required.

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HTTP_CLIENT_TIMEOUT

public static final intHTTP_CLIENT_TIMEOUT

HTTP Status-Code 408: Request Time-Out.

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HTTP_CONFLICT

public static final intHTTP_CONFLICT

HTTP Status-Code 409: Conflict.

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HTTP_GONE

public static final intHTTP_GONE

HTTP Status-Code 410: Gone.

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HTTP_LENGTH_REQUIRED

public static final intHTTP_LENGTH_REQUIRED

HTTP Status-Code 411: Length Required.

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HTTP_PRECON_FAILED

public static final intHTTP_PRECON_FAILED

HTTP Status-Code 412: Precondition Failed.

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HTTP_ENTITY_TOO_LARGE

public static final intHTTP_ENTITY_TOO_LARGE

HTTP Status-Code 413: Request Entity Too Large.

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HTTP_REQ_TOO_LONG

public static final intHTTP_REQ_TOO_LONG

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

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HTTP_UNSUPPORTED_TYPE

public static final intHTTP_UNSUPPORTED_TYPE

HTTP Status-Code 415: Unsupported Media Type.

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HTTP_SERVER_ERROR

public static final intHTTP_SERVER_ERROR

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

HTTP Status-Code 500: Internal Server Error.

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HTTP_INTERNAL_ERROR

public static final intHTTP_INTERNAL_ERROR

HTTP Status-Code 500: Internal Server Error.

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HTTP_NOT_IMPLEMENTED

public static final intHTTP_NOT_IMPLEMENTED

HTTP Status-Code 501: Not Implemented.

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HTTP_BAD_GATEWAY

public static final intHTTP_BAD_GATEWAY

HTTP Status-Code 502: Bad Gateway.

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HTTP_UNAVAILABLE

public static final intHTTP_UNAVAILABLE

HTTP Status-Code 503: Service Unavailable.

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HTTP_GATEWAY_TIMEOUT

public static final intHTTP_GATEWAY_TIMEOUT

HTTP Status-Code 504: Gateway Timeout.

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HTTP_VERSION

public static final intHTTP_VERSION

HTTP Status-Code 505: HTTP Version Not Supported.

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HttpURLConnection

protectedHttpURLConnection(URL u)

Constructor for the HttpURLConnection.

Parameters:

u - the URL

getHeaderFieldKey

publicStringgetHeaderFieldKey(int n)

Returns the key for then^th header field. Some implementations may treat the0^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, butgetHeaderFieldKey(0) returns null.

Overrides:

getHeaderFieldKey in classURLConnection

Parameters:

n - an index, where n >=0.

Returns:

the key for then^th header field, ornull if the key does not exist.

setFixedLengthStreamingMode

public voidsetFixedLengthStreamingMode(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.

Since:

1.5

See Also:

setChunkedStreamingMode(int)

setChunkedStreamingMode

public voidsetChunkedStreamingMode(int chunklen)

This method is used to enable streaming of a HTTP request body without internal buffering, when the content length isnot 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

publicStringgetHeaderField(int n)

Returns the value for then^th header field. Some implementations may treat the0^th header field as special, i.e. as the status line returned by the HTTP server.

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

Overrides:

getHeaderField in classURLConnection

Parameters:

n - an index, where n>=0.

Returns:

the value of then^th header field, ornull if the value does not exist.

See Also:

getHeaderFieldKey(int)

setFollowRedirects

public static voidsetFollowRedirects(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'scheckSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

Parameters:

set - aboolean indicating whether or not to follow HTTP redirects.

Throws:

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

See Also:

SecurityManager.checkSetFactory(),getFollowRedirects()

getFollowRedirects

public static booleangetFollowRedirects()

Returns aboolean 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 voidsetInstanceFollowRedirects(boolean followRedirects)

Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by thisHttpURLConnection instance.

The default value comes from followRedirects, which defaults to true.

Parameters:

followRedirects - aboolean indicating whether or not to follow HTTP redirects.

Since:

1.3

See Also:

instanceFollowRedirects,getInstanceFollowRedirects()

getInstanceFollowRedirects

public booleangetInstanceFollowRedirects()

Returns the value of thisHttpURLConnection'sinstanceFollowRedirects field.

Returns:

the value of thisHttpURLConnection'sinstanceFollowRedirects field.

Since:

1.3

See Also:

instanceFollowRedirects,setInstanceFollowRedirects(boolean)

setRequestMethod

public voidsetRequestMethod(String method)                      throwsProtocolException

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

publicStringgetRequestMethod()

Get the request method.

Returns:

the HTTP request method

See Also:

setRequestMethod(java.lang.String)

getResponseCode

public intgetResponseCode()                    throwsIOException

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

publicStringgetResponseMessage()                          throwsIOException

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, ornull

Throws:

IOException - if an error occurred connecting to the server.

getHeaderFieldDate

public longgetHeaderFieldDate(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 ofgetHeaderField 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 classURLConnection

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 theDefault argument is returned if the field is missing or malformed.

disconnect

public abstract voiddisconnect()

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 booleanusingProxy()

Indicates if the connection is going through a proxy.

Returns:

a boolean indicating if the connection is using a proxy.

getPermission

publicPermissiongetPermission()                         throwsIOException

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 returnsjava.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, aURLConnection representing afile: URL would return ajava.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 obtainedafter 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 testedbefore connecting.

Overrides:

getPermission in classURLConnection

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

publicInputStreamgetErrorStream()

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.