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Class HTTPClient.HttpURLConnection

java.lang.Object
   |
   +----java.net.URLConnection
           |
           +----java.net.HttpURLConnection
                   |
                   +----HTTPClient.HttpURLConnection

public class HttpURLConnection
extends HttpURLConnection
implements GlobalConstants
This class is a wrapper around HTTPConnection providing the interface defined by java.net.URLConnection and java.net.HttpURLConnection.

This class can be used to replace the HttpClient in the JDK with this HTTPClient by defining the property java.protocol.handler.pkgs=HTTPClient.

One difference between Sun's HttpClient and this one is that this one will provide you with a real output stream if possible. This leads to two changes: you should set the request property "Content-Length", if possible, before invoking getOutputStream(); and in many cases getOutputStream() implies connect(). This should be transparent, though, apart from the fact that you can't change any headers or other settings anymore once you've gotten the output stream. So, for large data do:

   HttpURLConnection con = (HttpURLConnection) url.openConnection();
   con.setDoOutput(true);
   con.setRequestProperty("Content-Length", ...);
   OutputStream out = con.getOutputStream();
   out.write(...);
   out.close();
   if (con.getResponseCode() != 200)
       ...
 

The HTTPClient will send the request data using the chunked transfer encoding when no Content-Length is specified and the server is HTTP/1.1 compatible. Because cgi-scripts can't usually handle this, you may experience problems trying to POST data. For this reason, whenever the Content-Type is application/x-www-form-urlencoded getOutputStream() will buffer the data before sending it so as prevent chunking. If you are sending requests with a different Content-Type and are experiencing problems then you may want to try setting the system property HTTPClient.dontChunkRequests to true (this needs to be done either on the command line or somewhere in the code before the first URLConnection.openConnection() is invoked).

Version:
0.3-2 18/06/1999
Author:
Ronald Tschalär

Constructor Index

 o HttpURLConnection(URL)
Construct a connection to the specified url.

Method Index

 o connect()
Connects to the server (if connection not still kept alive) and issues the request.
 o disconnect()
Closes all the connections to this server.
 o getDefaultRequestProperty(String)
Gets the value for a given default request header.
 o getErrorStream()
Returns the error stream if the connection failed but the server sent useful data nonetheless.
 o getHeaderField(int)
Gets header value of the n-th header.
 o getHeaderField(String)
Get the value part of a header.
 o getHeaderFieldDate(String, long)
Get the value part of a header, interprets it as a date and converts it to a long representing the number of milliseconds since 1970.
 o getHeaderFieldInt(String, int)
Get the value part of a header and converts it to an int.
 o getHeaderFieldKey(int)
Gets header name of the n-th header.
 o getInputStream()
Gets an input stream from which the data in the response may be read.
 o getInstanceFollowRedirects()
 o getOutputStream()
Gets an output stream which can be used send an entity with the request.
 o getRequestMethod()
Return the request method used.
 o getRequestProperty(String)
Gets the value of a given request header.
 o getResponseCode()
Get the response code.
 o getResponseMessage()
Get the response message describing the response code.
 o getURL()
Gets the url for this connection.
 o setDefaultRequestProperty(String, String)
Sets an arbitrary default request header.
 o setIfModifiedSince(long)
Sets the If-Modified-Since header.
 o setInstanceFollowRedirects(boolean)
Enables or disables the automatic handling of redirection responses for this instance only.
 o setRequestMethod(String)
Sets the request method (e.g.
 o setRequestProperty(String, String)
Sets an arbitrary request header.
 o toString()
produces a string.
 o usingProxy()
Shows if request are being made through an http proxy or directly.

Constructors

 o HttpURLConnection
 public HttpURLConnection(URL url) throws ProtocolNotSuppException, IOException
Construct a connection to the specified url. A cache of HTTPConnections is used to maximize the reuse of these across multiple HttpURLConnections.
The default method is "GET".

Parameters:
url - the url of the request
Throws: ProtocolNotSuppException
if the protocol is not supported

Methods

 o setRequestMethod
 public void setRequestMethod(String method) throws ProtocolException
Sets the request method (e.g. "PUT" or "HEAD"). Can only be set before connect() is called.

Parameters:
method - the http method.
Throws: ProtocolException
if already connected.
Overrides:
setRequestMethod in class HttpURLConnection
 o getRequestMethod
 public String getRequestMethod()
Return the request method used.

Returns:
the http method.
Overrides:
getRequestMethod in class HttpURLConnection
 o getResponseCode
 public int getResponseCode() throws IOException
Get the response code. Calls connect() if not connected.

Returns:
the http response code returned.
Overrides:
getResponseCode in class HttpURLConnection
 o getResponseMessage
 public String getResponseMessage() throws IOException
Get the response message describing the response code. Calls connect() if not connected.

Returns:
the http response message returned with the response code.
Overrides:
getResponseMessage in class HttpURLConnection
 o getHeaderField
 public String getHeaderField(String name)
Get the value part of a header. Calls connect() if not connected.

Parameters:
name - the of the header.
Returns:
the value of the header, or null if no such header was returned.
Overrides:
getHeaderField in class URLConnection
 o getHeaderFieldInt
 public int getHeaderFieldInt(String name,
                              int def)
Get the value part of a header and converts it to an int. If the header does not exist or if its value could not be converted to an int then the default is returned. Calls connect() if not connected.

Parameters:
name - the of the header.
def - the default value to return in case of an error.
Returns:
the value of the header, or null if no such header was returned.
Overrides:
getHeaderFieldInt in class URLConnection
 o getHeaderFieldDate
 public long getHeaderFieldDate(String name,
                                long def)
Get the value part of a header, interprets it as a date and converts it to a long representing the number of milliseconds since 1970. If the header does not exist or if its value could not be converted to a date then the default is returned. Calls connect() if not connected.

Parameters:
name - the of the header.
def - the default value to return in case of an error.
Returns:
the value of the header, or def in case of an error.
Overrides:
getHeaderFieldDate in class URLConnection
 o getHeaderFieldKey
 public String getHeaderFieldKey(int n)
Gets header name of the n-th header. Calls connect() if not connected. The name of the 0-th header is null, even though it the 0-th header has a value.

Parameters:
n - which header to return.
Returns:
the header name, or null if not that many headers.
Overrides:
getHeaderFieldKey in class URLConnection
 o getHeaderField
 public String getHeaderField(int n)
Gets header value of the n-th header. Calls connect() if not connected. The value of 0-th header is the Status-Line (e.g. "HTTP/1.1 200 Ok").

Parameters:
n - which header to return.
Returns:
the header value, or null if not that many headers.
Overrides:
getHeaderField in class URLConnection
 o getInputStream
 public InputStream getInputStream() throws IOException
Gets an input stream from which the data in the response may be read. Calls connect() if not connected.

Returns:
an InputStream
Throws: ProtocolException
if input not enabled.
Overrides:
getInputStream in class URLConnection
See Also:
setDoInput
 o getErrorStream
 public InputStream getErrorStream()
Returns the error stream if the connection failed but the server sent useful data nonetheless.

This method will not cause a connection to be initiated.

Returns:
an InputStream, or null if either the connection hasn't been established yet or no error occured
See Also:
getErrorStream
 o getOutputStream
 public synchronized OutputStream getOutputStream() throws IOException
Gets an output stream which can be used send an entity with the request. Can be called multiple times, in which case always the same stream is returned.

The default request method changes to "POST" when this method is called. Cannot be called after connect().

If no Content-type has been set it defaults to application/x-www-form-urlencoded. Furthermore, if the Content-type is application/x-www-form-urlencoded then all output will be collected in a buffer before sending it to the server; otherwise an HttpOutputStream is used.

Returns:
an OutputStream
Throws: ProtocolException
if already connect()'ed, if output is not enabled or if the request method does not support output.
Overrides:
getOutputStream in class URLConnection
See Also:
setDoOutput, HttpOutputStream
 o getURL
 public URL getURL()
Gets the url for this connection. If we're connect()'d and the request was redirected then the url returned is that of the final request.

Returns:
the final url, or null if any exception occured.
Overrides:
getURL in class URLConnection
 o setIfModifiedSince
 public void setIfModifiedSince(long time)
Sets the If-Modified-Since header.

Parameters:
time - the number of milliseconds since 1970.
Overrides:
setIfModifiedSince in class URLConnection
 o setRequestProperty
 public void setRequestProperty(String name,
                                String value)
Sets an arbitrary request header.

Parameters:
name - the name of the header.
value - the value for the header.
Overrides:
setRequestProperty in class URLConnection
 o getRequestProperty
 public String getRequestProperty(String name)
Gets the value of a given request header.

Parameters:
name - the name of the header.
Returns:
the value part of the header, or null if no such header.
Overrides:
getRequestProperty in class URLConnection
 o setDefaultRequestProperty
 public static void setDefaultRequestProperty(String name,
                                              String value)
Sets an arbitrary default request header. All headers set here are automatically sent with each request.

Parameters:
name - the name of the header.
value - the value for the header.
 o getDefaultRequestProperty
 public static String getDefaultRequestProperty(String name)
Gets the value for a given default request header.

Parameters:
name - the name of the header.
Returns:
the value part of the header, or null if no such header.
 o setInstanceFollowRedirects
 public void setInstanceFollowRedirects(boolean set)
Enables or disables the automatic handling of redirection responses for this instance only. Cannot be called after connect().

Parameters:
set - enables automatic redirection handling if true.
 o getInstanceFollowRedirects
 public boolean getInstanceFollowRedirects()
Returns:
true if automatic redirection handling for this instance is enabled.
 o connect
 public synchronized void connect() throws IOException
Connects to the server (if connection not still kept alive) and issues the request.

Overrides:
connect in class URLConnection
 o disconnect
 public void disconnect()
Closes all the connections to this server.

Overrides:
disconnect in class HttpURLConnection
 o usingProxy
 public boolean usingProxy()
Shows if request are being made through an http proxy or directly.

Returns:
true if an http proxy is being used.
Overrides:
usingProxy in class HttpURLConnection
 o toString
 public String toString()
produces a string.

Returns:
a string containing the HttpURLConnection
Overrides:
toString in class URLConnection

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