net.sourceforge.jtds.jdbc
Class SharedSocket

java.lang.Object
  net.sourceforge.jtds.jdbc.SharedSocket

Direct Known Subclasses:

SharedLocalNamedPipe, SharedNamedPipe

class SharedSocket

extends java.lang.Object

This class manages the physical connection to the SQL Server and serialises its use amongst a number of virtual sockets. This allows one physical connection to service a number of concurrent statements.

Constraints and assumptions:

1. Callers will not attempt to read from the server without issuing a request first.
2. The end of a server reply can be identified as byte 2 of the header is non zero.

Comments:

1. This code will discard unread server data if a new request is issued. Currently the higher levels of the driver attempt to do this but may be we can just rely on this code instead.
2. A cancel can be issued by a caller only if the server is currently sending data for the caller otherwise the cancel is ignored.
3. Cancel packets on their own are returned as extra records appended to the previous packet so that the TdsCore module can process them.

This version of the class will start to cache results to disk once a predetermined maximum buffer memory threshold has been passed. Small result sets that will fit within a specified limit (default 8 packets) will continue to be held in memory (even if the memory threshold has been passed) in the interests of efficiency.

Author:

Mike Hutchinson, Holger Rehn

Nested Class Summary

(package private) static class

SharedSocket.VirtualSocket This inner class contains the state information for the virtual socket.

Field Summary

private java.io.File	bufferDir The directory to buffer data to.
private java.lang.Object	cancelMonitor Synchronization monitor for cancelPending and responseOwner.
private boolean	cancelPending A cancel packet is pending.
private CharsetInfo	charsetInfo The character set to use for converting strings to/from bytes.
private byte[]	doneBuffer Buffer for TDS_DONE packets
private int	doneBufferFrag How much of the doneBuffer has been filled with data,
private static int	globalMemUsage Total memory usage in all instances of the driver NB.
private byte[]	hdrBuf Buffer for packet header.
private java.lang.String	host The server host name.
private java.io.DataInputStream	in Input stream for network socket.
private int	maxBufSize Current maximum input buffer size.
private static int	memoryBudget Max memory limit to use for buffers.
private static int	minMemPkts Minimum number of packets that will be cached in memory before the driver tries to write to disk even if memoryBudget has been exceeded.
private java.io.DataOutputStream	out Output stream for network socket.
private int	packetCount Count of packets received.
private static int	peakMemUsage Peak memory usage for debug purposes.
private int	port The server port number.
private SharedSocket.VirtualSocket	responseOwner The virtual socket of the object that is expecting a response from the server.
private static boolean	securityViolation Global flag to indicate that security constraints mean that attempts to create work files will fail.
protected int	serverType The servertype one of Driver.SQLSERVER or Driver.SYBASE
private java.net.Socket	socket The shared network socket.
private java.util.ArrayList	socketTable Table of stream objects sharing this socket.
private java.net.Socket	sslSocket The shared SSL network socket;
private static int	TDS_DONE_LEN Length of a TDS_DONE token.
private static int	TDS_DONE_TOKEN TDS done token.
private static int	TDS_HDR_LEN Length of TDS packet header.
private int	tdsVersion Tds protocol version

Constructor Summary

(package private)	SharedSocket(ConnectionJDBC2 connection) Construct a SharedSocket object specifying host name and port.
protected	SharedSocket(java.io.File bufferDir, int tdsVersion, int serverType)

Method Summary

(package private) boolean	cancel(SharedSocket.VirtualSocket vsock) Send a TDS cancel packet to the server.
(package private) void	close() Close the socket and release all resources.
(package private) void	closeStream(SharedSocket.VirtualSocket vsock) Deallocate a stream linked to this socket.
private java.net.Socket	createSocketForJDBC3(ConnectionJDBC2 connection) Creates a SharedSocket.VirtualSocket through reflection when Driver.JDBC3 is true.
private byte[]	dequeueInput(SharedSocket.VirtualSocket vsock) Read a cached packet from the in memory queue or from a disk based queue.
(package private) void	disableEncryption() Disable TLS encryption and switch back to raw TCP/IP socket.
(package private) void	enableEncryption(java.lang.String ssl) Enable TLS encryption by creating a TLS socket over the existing TCP/IP network socket.
private void	enqueueInput(SharedSocket.VirtualSocket vsock, byte[] buffer) Save a packet buffer in a memory queue or to a disk queue if the global memory limit for the driver has been exceeded.
protected void	finalize() Ensure all resources are released.
(package private) void	forceClose() Force close the socket causing any pending reads/writes to fail.
(package private) java.lang.String	getCharset() Retrieve the character set name used to translate byte arrays to or from Strings.
(package private) CharsetInfo	getCharsetInfo() Retrieve the character set descriptor used to translate byte arrays to or from Strings.
protected java.lang.String	getHost() Get the server host name.
protected java.io.DataInputStream	getIn() Getter for in field.
(package private) static int	getMemoryBudget() Get the global buffer memory limit for all instancs of this driver.
(package private) static int	getMinMemPkts() Get the minimum number of memory cached packets.
(package private) byte[]	getNetPacket(SharedSocket.VirtualSocket vsock, byte[] buffer) Get a network packet.
protected java.io.DataOutputStream	getOut() Getter for out field.
(package private) static int	getPktLen(byte[] buf) Convert two bytes (in network byte order) in a byte array into a Java short integer.
protected int	getPort() Get the server port number.
(package private) RequestStream	getRequestStream(int bufferSize, int maxPrecision) Obtain an instance of a server request stream for this socket.
(package private) ResponseStream	getResponseStream(RequestStream requestStream, int bufferSize) Obtain an instance of a server response stream for this socket.
(package private) int	getTdsVersion() Retrieve the TDS version that is active on the connection supported by this socket.
(package private) boolean	isConnected() Get the connected status of this socket.
private byte[]	readPacket(byte[] buffer) Read a physical TDS packet from the network.
(package private) byte[]	sendNetPacket(SharedSocket.VirtualSocket vsock, byte[] buffer) Send a network packet.
(package private) void	setCharsetInfo(CharsetInfo charsetInfo) Set the character set descriptor to be used to translate byte arrays to or from Strings.
protected void	setIn(java.io.DataInputStream in) Setter for in field.
protected void	setKeepAlive(boolean keepAlive) Set the socket keep alive.
(package private) static void	setMemoryBudget(int memoryBudget) Set the global buffer memory limit for all instances of this driver.
(package private) static void	setMinMemPkts(int minMemPkts) Set the minimum number of packets to cache in memory before writing to disk.
protected void	setOut(java.io.DataOutputStream out) Setter for out field.
protected void	setTdsVersion(int tdsVersion) Set the TDS version field.
protected void	setTimeout(int timeout) Set the socket timeout.

Methods inherited from class java.lang.Object

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

Field Detail

socket

private java.net.Socket socket

The shared network socket.

sslSocket

private java.net.Socket sslSocket

The shared SSL network socket;

out

private java.io.DataOutputStream out

Output stream for network socket.

in

private java.io.DataInputStream in

Input stream for network socket.

maxBufSize

private int maxBufSize

Current maximum input buffer size.

socketTable

private final java.util.ArrayList socketTable

Table of stream objects sharing this socket.

responseOwner

private SharedSocket.VirtualSocket responseOwner

The virtual socket of the object that is expecting a response from the server.

hdrBuf

private final byte[] hdrBuf

Buffer for packet header.

bufferDir

private final java.io.File bufferDir

The directory to buffer data to.

globalMemUsage

private static int globalMemUsage

Total memory usage in all instances of the driver NB. Access to this field should probably be synchronized but in practice lost updates will not matter much and I think all VMs tend to do atomic saves to integer variables.

peakMemUsage

private static int peakMemUsage

Peak memory usage for debug purposes.

memoryBudget

private static int memoryBudget

Max memory limit to use for buffers. Only when this limit is exceeded will the driver start caching to disk.

minMemPkts

private static int minMemPkts

Minimum number of packets that will be cached in memory before the driver tries to write to disk even if memoryBudget has been exceeded.

securityViolation

private static boolean securityViolation

Global flag to indicate that security constraints mean that attempts to create work files will fail.

tdsVersion

private int tdsVersion

Tds protocol version

serverType

protected final int serverType

The servertype one of Driver.SQLSERVER or Driver.SYBASE

charsetInfo

private CharsetInfo charsetInfo

The character set to use for converting strings to/from bytes.

packetCount

private int packetCount

Count of packets received.

host

private java.lang.String host

The server host name.

port

private int port

The server port number.

cancelPending

private boolean cancelPending

A cancel packet is pending.

cancelMonitor

private final java.lang.Object cancelMonitor

Synchronization monitor for cancelPending and responseOwner.

doneBuffer

private final byte[] doneBuffer

Buffer for TDS_DONE packets

doneBufferFrag

private int doneBufferFrag

How much of the doneBuffer has been filled with data,

TDS_DONE_TOKEN

private static final int TDS_DONE_TOKEN

TDS done token.

See Also:

Constant Field Values

TDS_DONE_LEN

private static final int TDS_DONE_LEN

Length of a TDS_DONE token.

See Also:

Constant Field Values

TDS_HDR_LEN

private static final int TDS_HDR_LEN

Length of TDS packet header.

See Also:

Constant Field Values

Constructor Detail

SharedSocket

protected SharedSocket(java.io.File bufferDir,
                       int tdsVersion,
                       int serverType)

SharedSocket

SharedSocket(ConnectionJDBC2 connection)
       throws java.io.IOException,
              java.net.UnknownHostException

Construct a SharedSocket object specifying host name and port.

Parameters:

connection - the connection object

Throws:

java.io.IOException - if socket open fails

java.net.UnknownHostException

Method Detail

createSocketForJDBC3

private java.net.Socket createSocketForJDBC3(ConnectionJDBC2 connection)
                                      throws java.io.IOException

Creates a SharedSocket.VirtualSocket through reflection when Driver.JDBC3 is true. Reflection must be used to stay compatible with JDK 1.3.

Parameters:

connection - the connection object

Returns:

a socket open to the host and port with the given timeout

Throws:

java.io.IOException - if socket open fails

enableEncryption

void enableEncryption(java.lang.String ssl)
                throws java.io.IOException

Enable TLS encryption by creating a TLS socket over the existing TCP/IP network socket.

Parameters:

ssl - the SSL URL property value

Throws:

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

disableEncryption

void disableEncryption()
                 throws java.io.IOException

Disable TLS encryption and switch back to raw TCP/IP socket.

Throws:

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

setCharsetInfo

void setCharsetInfo(CharsetInfo charsetInfo)

Set the character set descriptor to be used to translate byte arrays to or from Strings.

Parameters:

charsetInfo - the character set descriptor

getCharsetInfo

CharsetInfo getCharsetInfo()

Retrieve the character set descriptor used to translate byte arrays to or from Strings.

getCharset

java.lang.String getCharset()

Retrieve the character set name used to translate byte arrays to or from Strings.

Returns:

the character set name as a String

getRequestStream

RequestStream getRequestStream(int bufferSize,
                               int maxPrecision)

Obtain an instance of a server request stream for this socket.

Parameters:

bufferSize - the initial buffer size to be used by the RequestStream

maxPrecision - the maximum precision for numeric/decimal types

Returns:

the server request stream as a RequestStream

getResponseStream

ResponseStream getResponseStream(RequestStream requestStream,
                                 int bufferSize)

Obtain an instance of a server response stream for this socket. NB. getRequestStream() must be used first to obtain the RequestStream needed as a parameter for this method.

Parameters:

requestStream - an existing server request stream object obtained from this SharedSocket

bufferSize - the initial buffer size to be used by the RequestStream

Returns:

the server response stream as a ResponseStream

getTdsVersion

int getTdsVersion()

Retrieve the TDS version that is active on the connection supported by this socket.

Returns:

the TDS version as an int

setTdsVersion

protected void setTdsVersion(int tdsVersion)

Set the TDS version field.

Parameters:

tdsVersion - the TDS version as an int

setMemoryBudget

static void setMemoryBudget(int memoryBudget)

Set the global buffer memory limit for all instances of this driver.

Parameters:

memoryBudget - the global memory budget

getMemoryBudget

static int getMemoryBudget()

Get the global buffer memory limit for all instancs of this driver.

Returns:

the memory limit as an int

setMinMemPkts

static void setMinMemPkts(int minMemPkts)

Set the minimum number of packets to cache in memory before writing to disk.

Parameters:

minMemPkts - the minimum number of packets to cache

getMinMemPkts

static int getMinMemPkts()

Get the minimum number of memory cached packets.

Returns:

minimum memory packets as an int

isConnected

boolean isConnected()

Get the connected status of this socket.

Returns:

true if the underlying socket is connected

cancel

boolean cancel(SharedSocket.VirtualSocket vsock)

Send a TDS cancel packet to the server.

Parameters:

vsock - the SharedSocket.VirtualSocket used by the request to be canceled

Returns:

if a cancel is actually issued by this method call

close

void close()
     throws java.io.IOException

Close the socket and release all resources.

Throws:

java.io.IOException - if the socket close fails

forceClose

void forceClose()

Force close the socket causing any pending reads/writes to fail.

Used by the login timer to abort a login attempt.

closeStream

void closeStream(SharedSocket.VirtualSocket vsock)

Deallocate a stream linked to this socket.

Parameters:

vsock - the SharedSocket.VirtualSocket to close

sendNetPacket

byte[] sendNetPacket(SharedSocket.VirtualSocket vsock,
                     byte[] buffer)
               throws java.io.IOException

Send a network packet. If output for another virtual socket is in progress this packet will be sent later.

Parameters:

vsock - SharedSocket.VirtualSocket of the originating RequestStream

buffer - the data to send

Returns:

the same buffer received if emptied or another buffer w/ the same size if the incoming buffer is cached (to avoid copying)

Throws:

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

getNetPacket

byte[] getNetPacket(SharedSocket.VirtualSocket vsock,
                    byte[] buffer)
              throws java.io.IOException

Get a network packet. This may be read from the network directly or from previously cached buffers.

Parameters:

vsock - SharedSocket.VirtualSocket the originating ResponseStream object

buffer - the data buffer to receive the object (may be replaced)

Returns:

the data in a byte[] buffer

Throws:

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

enqueueInput

private void enqueueInput(SharedSocket.VirtualSocket vsock,
                          byte[] buffer)
                   throws java.io.IOException

Save a packet buffer in a memory queue or to a disk queue if the global memory limit for the driver has been exceeded.

Parameters:

vsock - the virtual socket owning this data

buffer - the data to queue

Throws:

java.io.IOException

dequeueInput

private byte[] dequeueInput(SharedSocket.VirtualSocket vsock)
                     throws java.io.IOException

Read a cached packet from the in memory queue or from a disk based queue.

Parameters:

vsock - the virtual socket owning this data

Returns:

a buffer containing the packet

Throws:

java.io.IOException

readPacket

private byte[] readPacket(byte[] buffer)
                   throws java.io.IOException

Read a physical TDS packet from the network.

Parameters:

buffer - a buffer to read the data into (if it fits) or null

Returns:

either the incoming buffer if it was large enough or a newly allocated buffer with the read packet

Throws:

java.io.IOException

getPktLen

static int getPktLen(byte[] buf)

Convert two bytes (in network byte order) in a byte array into a Java short integer.

Parameters:

buf - array of data

Returns:

the 16 bit unsigned value as an int

setTimeout

protected void setTimeout(int timeout)
                   throws java.net.SocketException

Set the socket timeout.

Parameters:

timeout - the timeout value in milliseconds

Throws:

java.net.SocketException

setKeepAlive

protected void setKeepAlive(boolean keepAlive)
                     throws java.net.SocketException

Set the socket keep alive.

Parameters:

keepAlive - true to turn on socket keep alive

Throws:

java.net.SocketException

getIn

protected java.io.DataInputStream getIn()

Getter for in field.

Returns:

InputStream used for communication

setIn

protected void setIn(java.io.DataInputStream in)

Setter for in field.

Parameters:

in - the InputStream to be used for communication

getOut

protected java.io.DataOutputStream getOut()

Getter for out field.

Returns:

OutputStream used for communication

setOut

protected void setOut(java.io.DataOutputStream out)

Setter for out field.

Parameters:

out - the OutputStream to be used for communication

getHost

protected java.lang.String getHost()

Get the server host name.

Returns:

the host name as a String

getPort

protected int getPort()

Get the server port number.

Returns:

the host port as an int

finalize

protected void finalize()
                 throws java.lang.Throwable

Ensure all resources are released.

Throws:

java.lang.Throwable