Package edu.caltech.nanodb.client

Class InteractiveClient

  • Direct Known Subclasses:
    ExclusiveClient, SharedServerClient
    public abstract class InteractiveClient
extends java.lang.Object
    This abstract class implements the basic functionality necessary for providing an interactive SQL client.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private static java.lang.String CMDPROMPT_FIRST
      A string constant specifying the "first-line" command-prompt.
      private static java.lang.String CMDPROMPT_NEXT
      A string constant specifying the "subsequent-lines" command-prompt.
      private java.lang.StringBuilder enteredText
      The buffer that accumulates each command's text.
      private boolean exiting
      A flag that records if we are exiting the interactive client.
      private static org.apache.logging.log4j.Logger logger  

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      private java.lang.String getCommandString()
      This helper method goes through the enteredText buffer, trying to identify the extent of the next command string.
      abstract CommandResult handleCommand​(java.lang.String command)
      Subclasses can implement this method to handle each command entered by the user.
      private void handleShellCommand​(java.lang.String shellCommand)
      Handle "shell commands," which are commands that the client itself handles on behalf of the user.
      protected void mainloop()
      This is the interactive mainloop that handles input from the standard input stream of the program.
      private void outputCommandResult​(CommandResult result)
      Outputs relevant information from the command-result object.
      private void processEnteredText()
      This helper function processes the contents of the enteredText field, consuming comments, handling client "shell commands" and regular commands that are handled by the NanoDBServer.
      abstract void shutdown()
      Shut down the interactive client.
      abstract void startup()
      Start up the interactive client.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • logger

        private static org.apache.logging.log4j.Logger logger

      • CMDPROMPT_FIRST

        private static final java.lang.String CMDPROMPT_FIRST
        A string constant specifying the "first-line" command-prompt.
        See Also:
        Constant Field Values

      • CMDPROMPT_NEXT

        private static final java.lang.String CMDPROMPT_NEXT
        A string constant specifying the "subsequent-lines" command-prompt.
        See Also:
        Constant Field Values

      • enteredText

        private java.lang.StringBuilder enteredText
        The buffer that accumulates each command's text.

      • exiting

        private boolean exiting
        A flag that records if we are exiting the interactive client.

    • Constructor Detail

      • InteractiveClient

        public InteractiveClient()

    • Method Detail

      • startup

        public abstract void startup()
                      throws java.lang.Exception
        Start up the interactive client. The specific way the client interacts with the server dictates how this startup mechanism will work.
        Throws:
        java.lang.Exception - if any error occurs during startup

      • mainloop

        protected void mainloop()
        This is the interactive mainloop that handles input from the standard input stream of the program.

      • processEnteredText

        private void processEnteredText()
        This helper function processes the contents of the enteredText field, consuming comments, handling client "shell commands" and regular commands that are handled by the NanoDBServer. Whatever command or comment is processed will also be removed from the enteredText buffer by this function. Note also that multiple commands will be processed, if present.

      • getCommandString

        private java.lang.String getCommandString()
        This helper method goes through the enteredText buffer, trying to identify the extent of the next command string. This is done using semicolons (that are not enclosed with single or double quotes). If a command is identified, it is removed from the internal buffer and returned. If no complete command is identified, null is returned.
        Returns:
        the first semicolon-terminated command in the internal data buffer, or null if the buffer contains no complete commands.

      • handleCommand

        public abstract CommandResult handleCommand​(java.lang.String command)
        Subclasses can implement this method to handle each command entered by the user. For example, a subclass may send the command over a socket to the server, wait for a response, then output the response to the console.
        Parameters:
        command - the command to handle.
        Returns:
        the command-result from executing the command

      • handleShellCommand

        private void handleShellCommand​(java.lang.String shellCommand)
        Handle "shell commands," which are commands that the client itself handles on behalf of the user. Shell commands start with a backslash "\" character.
        Parameters:
        shellCommand - the command to handle.

      • outputCommandResult

        private void outputCommandResult​(CommandResult result)
        Outputs relevant information from the command-result object.
        Parameters:
        result - the command-result object to output

      • shutdown

        public abstract void shutdown()
                       throws java.lang.Exception
        Shut down the interactive client. The specific way the client interacts with the server dictates how this shutdown mechanism will work.
        Throws:
        java.lang.Exception - if any error occurs during shutdown