org.acplt.oncrpc.web
Class HttpClientConnection

java.lang.Object
  org.acplt.oncrpc.web.HttpClientConnection

public class HttpClientConnection
extends java.lang.Object

The class HttpClientConnection provides a simple HTTP/1.1 compliant connection from a client to an HTTP server. This class does not provide a full-blown HTTP connection, but it is rather optimized for what ONC/RPC clients need in order to tunnel ONC remote procedure calls through ordinary HTTP connections, thus penetrating firewalls.

A HttpClientConnection is not that clever as you would first expect. Rather you have to do some things for yourself, like reconnecting dropped connections, and so on. While this sometimes result in more labour on the caller's shoulders, this keeps resource wasting at a minimum, and gives you full control over redirections and other mess -- you do want full control, right?.

For this reason, for instance, an HttpClientConnection does not buffer the whole request before sending it to the server but rather relies on the caller to supply the right content-length information. This avoids unnecessary double buffering but instead creates the bas64 encoded content on-the-fly.

Of course, this client connection object does not touch the content, it just suplies the pipe to swallow the data.

Nested Class Summary

(package private) class

HttpClientConnection.GetPropertyPrivilegedAction

Field Summary

private byte[]	asciiBuffer Buffer receiving ASCII characters from Unicode strings when sending (header) strings to the HTTP server.
private java.lang.String	cachedProxyHost Address of proxy host to contact instead of real HTTP server.
private int	cachedProxyPort Port number of proxy HTTP server.
private boolean	chunkedTransfer Indicates whether the HTTP server send its reply using the chunked transfer encoding.
private java.lang.String	contentType Type of content sent by HTTP server.
static byte[]	CRLF
private boolean	finalChunkSeen Indicates whether the end-of-chunks chunk has been read (whow, another one for the Purlitzer price).
private char[]	headerLine Dynamically growing buffer used during header parsing.
private java.lang.String	hostname Host name of HTTP server to contact in the form of www.acplt.org.
private static int	HTTP_DEAD
static int	HTTP_DEFAULTPORT Default port where HTTP servers listen for incomming requests.
private static int	HTTP_IDLE
private static int	HTTP_RECEIVING
private static int	HTTP_SENDING
private java.io.InputStream	in
private boolean	keepAlive
private int	mode Indicates sending/receiving mode of the HTTP connection.
private java.io.OutputStream	out Buffered output stream used for sending the HTTP headers.
private int	port Port number where to contact the HTTP server.
private int	remainingChunkLength Contains the amount of data still to be read for the current chunk.
private int	remainingContentLength Indicates the amount of content data which still has to be sent or received.
private int	responseCode Contains the HTTP response code from the last request sent to the HTTP server.
private java.net.Socket	socket TCP/IP socket for communication with the HTTP server.
private int	timeout Timeout (in milliseconds) for communication with an HTTP server.
private boolean	useProxy Indicates whether a proxy HTTP server needs to be contacted in order to reach the real HTTP server.
private java.lang.String	userAgentId

Constructor Summary

HttpClientConnection(java.lang.String hostname)
Constructs a new HttpClientConnection.

HttpClientConnection(java.lang.String hostname, int port)
Constructs a new HttpClientConnection.

Method Summary

int	beginDecoding() Begin receiving the content sent by the HTTP server.
void	beginPostRequest(java.lang.String path, java.lang.String mimeType, int contentLength) Starts a new HTTP "POST" request and sends all necessary HTTP header fields.
void	close() Closes the connection to the HTTP server and frees up some resources.
private void	connect() Connects to the HTTP server.
void	endDecoding() This method silently discards any unread content, if the caller has yet not read all content.
void	endPostRequest() Ends the HTTP "POST" request.
java.lang.String	getContentType() Returns the content type (MIME type, charset, etc.).
boolean	getKeepAlive()
private java.lang.String	getProxyHost() Retrieves the host name where the HTTP proxy server resided from the system properties.
private int	getProxyPort() Retrieves the port number where the HTTP proxy server resides from the system properties.
int	getRemainingContentLength() Returns amount of content still available (to be read).
int	getResponseCode()
int	getTimeout() Retrieve the current timeout set for remote procedure calls.
protected void	handleOption(java.lang.String option, java.lang.String value) Handle options sent by the HTTP server.
int	readContentBytes(byte[] buffer, int offset, int length) Read content sent by the HTTP server.
private boolean	readHeaderLine(java.lang.String[] keyvalue) Read in a header line coming over the HTTP connection from the server.
private int	readHeaders() Read the HTTP headers sent by the servers and also parse them at the same time.
private java.lang.String	readLine() Read exactly one line, termined by CRLF or either CR or LF, and return it.
void	setTimeout(int milliseconds) Set the timout for sending or receiving information to/from the HTTP server.
private void	write(java.lang.String s) Writes an ASCII string to the HTTP server (this is buffered first).
void	writeContentBytes(byte[] bytes, int offset, int length) Send (part) of the content to the HTTP server.
private void	writeln(java.lang.String s) Writes an ASCII string and appends a line termination in the form of CR followed by LF.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

HTTP_DEFAULTPORT

public static final int HTTP_DEFAULTPORT

Default port where HTTP servers listen for incomming requests. This is just a convenience definition to make the code more readable.

See Also:

Constant Field Values

hostname

private java.lang.String hostname

Host name of HTTP server to contact in the form of www.acplt.org.

port

private int port

Port number where to contact the HTTP server. This defaults to the standard port where HTTP servers are expected: port 80.

socket

private java.net.Socket socket

TCP/IP socket for communication with the HTTP server.

timeout

private int timeout

Timeout (in milliseconds) for communication with an HTTP server.

keepAlive

private boolean keepAlive

chunkedTransfer

private boolean chunkedTransfer

Indicates whether the HTTP server send its reply using the chunked transfer encoding.

remainingChunkLength

private int remainingChunkLength

Contains the amount of data still to be read for the current chunk.

finalChunkSeen

private boolean finalChunkSeen

Indicates whether the end-of-chunks chunk has been read (whow, another one for the Purlitzer price).

contentType

private java.lang.String contentType

Type of content sent by HTTP server.

out

private java.io.OutputStream out

Buffered output stream used for sending the HTTP headers. This stream is not used to send content in an HTTP request.

in

private java.io.InputStream in

responseCode

private int responseCode

Contains the HTTP response code from the last request sent to the HTTP server.

asciiBuffer

private byte[] asciiBuffer

Buffer receiving ASCII characters from Unicode strings when sending (header) strings to the HTTP server.

headerLine

private char[] headerLine

Dynamically growing buffer used during header parsing.

userAgentId

private java.lang.String userAgentId

HTTP_DEAD

private static final int HTTP_DEAD

See Also:

Constant Field Values

HTTP_IDLE

private static final int HTTP_IDLE

See Also:

Constant Field Values

HTTP_SENDING

private static final int HTTP_SENDING

See Also:

Constant Field Values

HTTP_RECEIVING

private static final int HTTP_RECEIVING

See Also:

Constant Field Values

mode

private int mode

Indicates sending/receiving mode of the HTTP connection.

remainingContentLength

private int remainingContentLength

Indicates the amount of content data which still has to be sent or received.

CRLF

public static final byte[] CRLF

useProxy

private boolean useProxy

Indicates whether a proxy HTTP server needs to be contacted in order to reach the real HTTP server.

cachedProxyHost

private java.lang.String cachedProxyHost

Address of proxy host to contact instead of real HTTP server.

cachedProxyPort

private int cachedProxyPort

Port number of proxy HTTP server.

Constructor Detail

HttpClientConnection

public HttpClientConnection(java.lang.String hostname)

Constructs a new HttpClientConnection. The port used on the HTTP server side is the default HTTP port, 80.

Parameters:

hostname - name (DNS name or IP dotted address) of host running a HTTP server to which we want to connect to.

HttpClientConnection

public HttpClientConnection(java.lang.String hostname,
                            int port)

Constructs a new HttpClientConnection.

Parameters:

hostname - name (DNS name or IP dotted address) of host running a HTTP server to which we should connect to.

port - Port number where the HTTP server can be contacted.

Method Detail

close

public void close()

Closes the connection to the HTTP server and frees up some resources. After calling close it is still possible to open a new connection to the HTTP server once again.

beginPostRequest

public void beginPostRequest(java.lang.String path,
                             java.lang.String mimeType,
                             int contentLength)
                      throws java.io.IOException

Starts a new HTTP "POST" request and sends all necessary HTTP header fields. Next, the caller can send lots of content using the writeContentBytes(byte[], int, int) method. Finally, to finish the request he has to call the endPostRequest() method.

Parameters:

path - Path to server object which handles the POST request. For instance, this can be a CGI script (although it better should not be one, except in the case of FAST CGI).

mimeType - MIME-classified type of content to be sent.

contentLength - Length of content to be sent. If negative, the length is not known in advance. In this case, keeping the connection alive is not possible, so callers should avoid this situation, if possible.

Throws:

java.io.IOException - if an I/O exception occurs when sending the HTTP headers. In this case the connection is closed automatically and the caller must not send any content. However, the caller is free to give the request another try by calling beginEncoding again, thus opening a new HTTP connection.

writeContentBytes

public void writeContentBytes(byte[] bytes,
                              int offset,
                              int length)
                       throws java.io.IOException

Send (part) of the content to the HTTP server. Note that the output is done unbuffered, so callers should write their content in large chunks to avoid the calling overhead for sending data.

Parameters:

bytes - The data.

offset - Start offset in the data.

length - Number of bytes to write.

Throws:

java.lang.RuntimeException - if too much content was sent.

java.io.IOException - if an I/O error occurs.

java.lang.NullPointerException - if bytes is null.

java.lang.IndexOutOfBoundsException - if offset is negative, or length is negative, or offset + length is greater than the length of the array bytes.

endPostRequest

public void endPostRequest()
                    throws java.io.IOException

Ends the HTTP "POST" request. The next logical step for a caller is then to call ... #FIXME

Throws:

java.io.IOException

handleOption

protected void handleOption(java.lang.String option,
                            java.lang.String value)

Handle options sent by the HTTP server.

Currently the following options are handled by this class:

• Content-Length -- length of content following the header section
• Content-Type -- type of content sent
• Proxy-Connection -- handle keep-alive request
• Connection -- handle keep-alive request
• Transfer-Encoding -- transfer encoding choosen by HTTP server

Parameters:

option - Name of option sent by HTTP server.

value - Value of option.

readHeaders

private int readHeaders()
                 throws java.io.IOException

Read the HTTP headers sent by the servers and also parse them at the same time.

Returns:

HTTP status code.

Throws:

java.io.IOException

readHeaderLine

private boolean readHeaderLine(java.lang.String[] keyvalue)
                        throws java.io.IOException

Read in a header line coming over the HTTP connection from the server.

Parameters:

keyvalue - An array with room for either exactly one or two strings, receiving the header option and optionally its value. If only room for a single return string is supplied, then readHeaderLine will only read in the header line (like the first HTTP header) without separating the options's value from its name. If a header option has no option, then null is returned as the value string.

Returns:

false if the end of the headers has been reached.

Throws:

java.io.IOException

readLine

private java.lang.String readLine()
                           throws java.io.IOException

Read exactly one line, termined by CRLF or either CR or LF, and return it.

Returns:

Line without the terminating CR, LF or CRLF.

Throws:

java.io.IOException

beginDecoding

public int beginDecoding()
                  throws java.io.IOException

Begin receiving the content sent by the HTTP server. This method blocks until at least the HTTP header section has been received or until the connection times out.

Returns:

HTTP server response code (status code).

Throws:

java.io.IOException

getContentType

public java.lang.String getContentType()

Returns the content type (MIME type, charset, etc.).

Returns:

content type

readContentBytes

public int readContentBytes(byte[] buffer,
                            int offset,
                            int length)
                     throws java.io.IOException

Read content sent by the HTTP server. This method also handles the HTTP/1.1 chunked transfer encoding if the HTTP server insisted on using it. If only chunked transfer encoding has been introduced with the first official 0.9 protocol version of HTTP, it would have made sending ONC/RPC requests much easier, because we would not need to buffer the while request before sending it just to know its exact length. Unfortunately, chunking has only been introduced lately so we can not expect servers and especially proxies to handle it. Sigh.

Parameters:

buffer - Buffer to receive the content sent by the HTTP server.

offset - Start offset in the buffer.

length - Number of bytes to receive.

Throws:

java.net.ProtocolException - if not enough content was available (the caller attempted to read more data than available) or if we received junk information violating the HTTP protocol specification.

java.io.IOException - if an I/O error occurs.

java.lang.NullPointerException - if bytes is null.

java.lang.IndexOutOfBoundsException - if offset is negative, or length is negative, or offset + length is greater than the length of the array bytes.

getRemainingContentLength

public int getRemainingContentLength()

Returns amount of content still available (to be read). This always shows the remaining amount and is updated whenever content is read using readContentBytes(byte[], int, int).

Returns:

Amount of content available.

endDecoding

public void endDecoding()
                 throws java.io.IOException

This method silently discards any unread content, if the caller has yet not read all content.

Throws:

java.io.IOException

setTimeout

public void setTimeout(int milliseconds)

Set the timout for sending or receiving information to/from the HTTP server.

Parameters:

milliseconds - Timeout in milliseconds.

getTimeout

public int getTimeout()

Retrieve the current timeout set for remote procedure calls. A timeout of zero indicates batching calls (no reply message is expected).

Returns:

Current timeout.

getResponseCode

public int getResponseCode()

getKeepAlive

public boolean getKeepAlive()

connect

private void connect()
              throws java.io.IOException

Connects to the HTTP server. In case an HTTP proxy has been configured, this connects to the proxy instead.

If the connection is in keep-alive mode and already open, then the connection is reused.

Throws:

java.lang.SecurityException - if a security manager exists and its checkConnect method does not allow the connect operation.

java.io.IOException

write

private void write(java.lang.String s)
            throws java.io.IOException

Writes an ASCII string to the HTTP server (this is buffered first).

Parameters:

s - String to write.

Throws:

java.io.IOException

writeln

private void writeln(java.lang.String s)
              throws java.io.IOException

Writes an ASCII string and appends a line termination in the form of CR followed by LF.

Parameters:

s - String to write.

Throws:

java.io.IOException

getProxyHost

private java.lang.String getProxyHost()

Retrieves the host name where the HTTP proxy server resided from the system properties.

Returns:

Name of proxy host or null if no proxy has been configured.

getProxyPort

private int getProxyPort()

Retrieves the port number where the HTTP proxy server resides from the system properties. If no port number has been configured for the HTTP proxy, then the default http port number of 80 is returned.

Returns:

Port number of HTTP proxy server.