Package net.sourceforge.jtds.jdbc

Class SharedSocket

java.lang.Object
net.sourceforge.jtds.jdbc.SharedSocket
Direct Known Subclasses:
SharedLocalNamedPipe, SharedNamedPipe
class SharedSocket extends 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

  • Field Details

    • socket

      private Socket socket
      The shared network socket.

    • sslSocket

      private Socket sslSocket
      The shared SSL network socket;

    • out

      private DataOutputStream out
      Output stream for network socket.

    • in

      private DataInputStream in
      Input stream for network socket.

    • maxBufSize

      private int maxBufSize
      Current maximum input buffer size.

    • _LastID

      private final AtomicInteger _LastID
      last ID assigned to a VirtualSocket instance

    • _VirtualSockets

      private final ConcurrentMap<Integer,SharedSocket.VirtualSocket> _VirtualSockets
      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 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 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 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, invalid input: '<'TDS_DONE_LEN IFF partial packet read.

    • TDS_DONE_TOKEN

      private static final int TDS_DONE_TOKEN
      TDS done token.
      See Also:

    • TDS_DONE_LEN

      private static final int TDS_DONE_LEN
      Length of a TDS_DONE token.
      See Also:

    • TDS_HDR_LEN

      private static final int TDS_HDR_LEN
      Length of TDS packet header.
      See Also:

  • Constructor Details

  • Method Details

    • createSocketForJDBC3

      private Socket createSocketForJDBC3(JtdsConnection connection) throws IOException
      Creates a Socket connection.
      Parameters:
      connection - the connection object
      Returns:
      a socket open to the host and port with the given timeout
      Throws:
      IOException - if socket open fails

    • getMAC

      String getMAC()

    • enableEncryption

      void enableEncryption(String ssl) throws IOException
      Enable TLS encryption by creating a TLS socket over the existing TCP/IP network socket.
      Parameters:
      ssl - the SSL URL property value
      Throws:
      IOException - if an I/O error occurs

    • disableEncryption

      void disableEncryption() throws IOException
      Disable TLS encryption and switch back to raw TCP/IP socket.
      Throws:
      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

      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:
      true if a cancel is actually issued by this method call

    • close

      void close() throws IOException
      Close the socket and release all resources.
      Throws:
      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 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:
      IOException - if an I/O error occurs

    • getNetPacket

      byte[] getNetPacket(SharedSocket.VirtualSocket vsock, byte[] buffer) throws 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:
      IOException - if an I/O error occurs

    • enqueueInput

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

    • dequeueInput

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

    • readPacket

      private byte[] readPacket(byte[] buffer) throws 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:
      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 SocketException
      Set the socket timeout.
      Parameters:
      timeout - the timeout value in milliseconds
      Throws:
      SocketException

    • setKeepAlive

      protected void setKeepAlive(boolean keepAlive) throws SocketException
      Set the socket keep alive.
      Parameters:
      keepAlive - true to turn on socket keep alive
      Throws:
      SocketException

    • getIn

      protected DataInputStream getIn()
      Getter for in field.
      Returns:
      InputStream used for communication

    • setIn

      protected void setIn(DataInputStream in)
      Setter for in field.
      Parameters:
      in - the InputStream to be used for communication

    • getOut

      protected DataOutputStream getOut()
      Getter for out field.
      Returns:
      OutputStream used for communication

    • setOut

      protected void setOut(DataOutputStream out)
      Setter for out field.
      Parameters:
      out - the OutputStream to be used for communication

    • getHost

      protected 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 Throwable
      Ensure all resources are released.
      Overrides:
      finalize in class Object
      Throws:
      Throwable