Module java.base
Package 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.

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:
1.1
See Also:
disconnect()

  • Field Details

  • Constructor Details

    • HttpURLConnection

      protected HttpURLConnection​(URL u)
      Constructor for the HttpURLConnection.
      Parameters:
      u - the URL

  • Method Details

    • setAuthenticator

      public void setAuthenticator​(Authenticator auth)
      Supplies an Authenticator to be used when authentication is requested through the HTTP protocol for this HttpURLConnection. If no authenticator is supplied, the default authenticator will be used.
      Implementation Requirements:
      The default behavior of this method is to unconditionally throw UnsupportedOperationException. Concrete implementations of HttpURLConnection which support supplying an Authenticator for a specific HttpURLConnection instance should override this method to implement a different behavior.
      Implementation Note:
      Depending on authentication schemes, an implementation may or may not need to use the provided authenticator to obtain a password. For instance, an implementation that relies on third-party security libraries may still invoke the default authenticator if these libraries are configured to do so. Likewise, an implementation that supports transparent NTLM authentication may let the system attempt to connect using the system user credentials first, before invoking the provided authenticator.
      However, if an authenticator is specifically provided, then the underlying connection may only be reused for HttpURLConnection instances which share the same Authenticator instance, and authentication information, if cached, may only be reused for an HttpURLConnection sharing that same Authenticator.
      Parameters:
      auth - The Authenticator that should be used by this HttpURLConnection.
      Throws:
      UnsupportedOperationException - if setting an Authenticator is not supported by the underlying implementation.
      IllegalStateException - if URLConnection is already connected.
      NullPointerException - if the supplied auth is null.
      Since:
      9

    • 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()

    • 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.

    • 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. This method returns true if the connection is known to be going or has gone through proxies, and returns false if the connection will never go through a proxy or if the use of a proxy cannot be determined.
      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.