path: root/src/interfaces/jdbc/postgresql/Connection.java

package postgresql;

import java.io.*;
import java.lang.*;
import java.net.*;
import java.util.*;
import java.sql.*;
import postgresql.*;

/**
 * @version 1.0 15-APR-1997
 * @author <A HREF="mailto:[email protected]">Adrian Hall</A>
 *
 * A Connection represents a session with a specific database.  Within the
 * context of a Connection, SQL statements are executed and results are
 * returned.
 *
 * A Connection's database is able to provide information describing
 * its tables, its supported SQL grammar, its stored procedures, the
 * capabilities of this connection, etc.  This information is obtained
 * with the getMetaData method.
 *
 * <B>Note:</B> By default, the Connection automatically commits changes
 * after executing each statement.  If auto-commit has been disabled, an
 * explicit commit must be done or database changes will not be saved.
 *
 * @see java.sql.Connection
 */
public class Connection implements java.sql.Connection 
{
  protected PG_Stream pg_stream;
  
  private String PG_HOST;
  private int PG_PORT;
  private String PG_USER;
  private String PG_PASSWORD;
  private String PG_DATABASE;
  private boolean PG_STATUS;
  
  public boolean CONNECTION_OK = true;
  public boolean CONNECTION_BAD = false;
  
  private int STARTUP_CODE = 7;
  
  private boolean autoCommit = true;
  private boolean readOnly = false;
  
  protected Driver this_driver;
  private String this_url;
  private String cursor = null;	// The positioned update cursor name
  
  /**
   * Connect to a PostgreSQL database back end.
   *
   * @param host the hostname of the database back end
   * @param port the port number of the postmaster process
   * @param info a Properties[] thing of the user and password
   * @param database the database to connect to
   * @param u the URL of the connection
   * @param d the Driver instantation of the connection
   * @return a valid connection profile
   * @exception SQLException if a database access error occurs
   */
  public Connection(String host, int port, Properties info, String database, String url, Driver d) throws SQLException
  {
    int len = 288;			// Length of a startup packet
    
    this_driver = d;
    this_url = new String(url);
    PG_DATABASE = new String(database);
    PG_PASSWORD = new String(info.getProperty("password"));
    PG_USER = new String(info.getProperty("user"));
    PG_PORT = port;
    PG_HOST = new String(host);
    PG_STATUS = CONNECTION_BAD;
    
    try
      {
	pg_stream = new PG_Stream(host, port);
      } catch (IOException e) {
	throw new SQLException ("Connection failed: " + e.toString());
      }
      
      // Now we need to construct and send a startup packet
      try
	{
	  pg_stream.SendInteger(len, 4);			len -= 4;
	  pg_stream.SendInteger(STARTUP_CODE, 4);		len -= 4;
	  pg_stream.Send(database.getBytes(), 64);	len -= 64;
	  pg_stream.Send(PG_USER.getBytes(), len);
	} catch (IOException e) {
	  throw new SQLException("Connection failed: " + e.toString());
	}
	ExecSQL(" ");				// Test connection
	PG_STATUS = CONNECTION_OK;
  }
  
  /**
   * SQL statements without parameters are normally executed using
   * Statement objects.  If the same SQL statement is executed many
   * times, it is more efficient to use a PreparedStatement
   *
   * @return a new Statement object
   * @exception SQLException passed through from the constructor
   */
  public java.sql.Statement createStatement() throws SQLException
  {
    return new Statement(this);
  }
  
  /**
   * A SQL statement with or without IN parameters can be pre-compiled
   * and stored in a PreparedStatement object.  This object can then
   * be used to efficiently execute this statement multiple times.
   *
   * <B>Note:</B> This method is optimized for handling parametric
   * SQL statements that benefit from precompilation if the drivers
   * supports precompilation.  PostgreSQL does not support precompilation.
   * In this case, the statement is not sent to the database until the
   * PreparedStatement is executed.  This has no direct effect on users;
   * however it does affect which method throws certain SQLExceptions
   *
   * @param sql a SQL statement that may contain one or more '?' IN
   *	parameter placeholders
   * @return a new PreparedStatement object containing the pre-compiled
   *	statement.
   * @exception SQLException if a database access error occurs.
   */
  public java.sql.PreparedStatement prepareStatement(String sql) throws SQLException
  {
    return new PreparedStatement(this, sql);
  }
  
  /**
   * A SQL stored procedure call statement is handled by creating a
   * CallableStatement for it.  The CallableStatement provides methods
   * for setting up its IN and OUT parameters and methods for executing
   * it.
   *
   * <B>Note:</B> This method is optimised for handling stored procedure
   * call statements.  Some drivers may send the call statement to the
   * database when the prepareCall is done; others may wait until the
   * CallableStatement is executed.  This has no direct effect on users;
   * however, it does affect which method throws certain SQLExceptions
   *
   * @param sql a SQL statement that may contain one or more '?' parameter
   *	placeholders.  Typically this statement is a JDBC function call
   *	escape string.
   * @return a new CallableStatement object containing the pre-compiled
   *	SQL statement
   * @exception SQLException if a database access error occurs
   */
  public java.sql.CallableStatement prepareCall(String sql) throws SQLException
  {
    throw new SQLException("Callable Statements are not supported at this time");
    //		return new CallableStatement(this, sql);
  }
  
  /**
   * A driver may convert the JDBC sql grammar into its system's
   * native SQL grammar prior to sending it; nativeSQL returns the
   * native form of the statement that the driver would have sent.
   *
   * @param sql a SQL statement that may contain one or more '?'
   *	parameter placeholders
   * @return the native form of this statement
   * @exception SQLException if a database access error occurs
   */
  public String nativeSQL(String sql) throws SQLException
  {
    return sql;
  }
  
  /**
   * If a connection is in auto-commit mode, than all its SQL
   * statements will be executed and committed as individual
   * transactions.  Otherwise, its SQL statements are grouped
   * into transactions that are terminated by either commit()
   * or rollback().  By default, new connections are in auto-
   * commit mode.  The commit occurs when the statement completes
   * or the next execute occurs, whichever comes first.  In the
   * case of statements returning a ResultSet, the statement
   * completes when the last row of the ResultSet has been retrieved
   * or the ResultSet has been closed.  In advanced cases, a single
   * statement may return multiple results as well as output parameter
   * values.  Here the commit occurs when all results and output param
   * values have been retrieved.
   *
   * @param autoCommit - true enables auto-commit; false disables it
   * @exception SQLException if a database access error occurs
   */
  public void setAutoCommit(boolean autoCommit) throws SQLException
  {
    if (this.autoCommit == autoCommit)
      return;
    if (autoCommit)
      ExecSQL("end");
    else
      ExecSQL("begin");
    this.autoCommit = autoCommit;
  }
  
  /**
   * gets the current auto-commit state
   * 
   * @return Current state of the auto-commit mode
   * @exception SQLException (why?)
   * @see setAutoCommit
   */
  public boolean getAutoCommit() throws SQLException
  {
    return this.autoCommit;
  }
  
  /**
   * The method commit() makes all changes made since the previous
   * commit/rollback permanent and releases any database locks currently
   * held by the Connection.  This method should only be used when
   * auto-commit has been disabled.  (If autoCommit == true, then we
   * just return anyhow)
   *
   * @exception SQLException if a database access error occurs
   * @see setAutoCommit
   */
  public void commit() throws SQLException
  {
    if (autoCommit)
      return;
    ExecSQL("commit");
    autoCommit = true;
    ExecSQL("begin");
    autoCommit = false;
  }
  
  /**
   * The method rollback() drops all changes made since the previous
   * commit/rollback and releases any database locks currently held by
   * the Connection. 
   *
   * @exception SQLException if a database access error occurs
   * @see commit
   */
  public void rollback() throws SQLException
  {
    if (autoCommit)
      return;
    ExecSQL("rollback");
    autoCommit = true;
    ExecSQL("begin");
    autoCommit = false;
  }
  
  /**
   * In some cases, it is desirable to immediately release a Connection's
   * database and JDBC resources instead of waiting for them to be
   * automatically released (cant think why off the top of my head)
   *
   * <B>Note:</B> A Connection is automatically closed when it is
   * garbage collected.  Certain fatal errors also result in a closed
   * connection.
   *
   * @exception SQLException if a database access error occurs
   */
  public void close() throws SQLException
  {
    if (pg_stream != null)
      {
	try
	  {
	    pg_stream.close();
	  } catch (IOException e) {}
	  pg_stream = null;
      }
  }
  
  /**
   * Tests to see if a Connection is closed
   *
   * @return the status of the connection
   * @exception SQLException (why?)
   */
  public boolean isClosed() throws SQLException
  {
    return (pg_stream == null);
  }
  
  /**
   * A connection's database is able to provide information describing
   * its tables, its supported SQL grammar, its stored procedures, the
   * capabilities of this connection, etc.  This information is made
   * available through a DatabaseMetaData object.
   *
   * @return a DatabaseMetaData object for this connection
   * @exception SQLException if a database access error occurs
   */
  public java.sql.DatabaseMetaData getMetaData() throws SQLException
  {
    return new DatabaseMetaData(this);
  }
  
  /**
   * You can put a connection in read-only mode as a hunt to enable
   * database optimizations
   *
   * <B>Note:</B> setReadOnly cannot be called while in the middle
   * of a transaction
   *
   * @param readOnly - true enables read-only mode; false disables it
   * @exception SQLException if a database access error occurs
   */
  public void setReadOnly (boolean readOnly) throws SQLException
  {
    this.readOnly = readOnly;
  }
  
  /**
   * Tests to see if the connection is in Read Only Mode.  Note that
   * we cannot really put the database in read only mode, but we pretend
   * we can by returning the value of the readOnly flag
   *
   * @return true if the connection is read only
   * @exception SQLException if a database access error occurs
   */
  public boolean isReadOnly() throws SQLException
  {
    return readOnly;
  }
  
  /**
   * A sub-space of this Connection's database may be selected by
   * setting a catalog name.  If the driver does not support catalogs,
   * it will silently ignore this request
   *
   * @exception SQLException if a database access error occurs
   */
  public void setCatalog(String catalog) throws SQLException
  {
    // No-op
  }
  
  /**
   * Return the connections current catalog name, or null if no
   * catalog name is set, or we dont support catalogs.
   *
   * @return the current catalog name or null
   * @exception SQLException if a database access error occurs
   */
  public String getCatalog() throws SQLException
  {
    return null;
  }
  
  /**
   * You can call this method to try to change the transaction
   * isolation level using one of the TRANSACTION_* values.  
   *
   * <B>Note:</B> setTransactionIsolation cannot be called while
   * in the middle of a transaction
   *
   * @param level one of the TRANSACTION_* isolation values with
   *	the exception of TRANSACTION_NONE; some databases may
   *	not support other values
   * @exception SQLException if a database access error occurs
   * @see java.sql.DatabaseMetaData#supportsTransactionIsolationLevel
   */
  public void setTransactionIsolation(int level) throws SQLException
  {
    throw new SQLException("Transaction Isolation Levels are not implemented");
  }
  
  /**
   * Get this Connection's current transaction isolation mode.
   * 
   * @return the current TRANSACTION_* mode value
   * @exception SQLException if a database access error occurs
   */
  public int getTransactionIsolation() throws SQLException
  {
    return java.sql.Connection.TRANSACTION_SERIALIZABLE;
  }
  
  /**
   * The first warning reported by calls on this Connection is
   * returned.
   *
   * <B>Note:</B> Sebsequent warnings will be changed to this
   * SQLWarning
   *
   * @return the first SQLWarning or null
   * @exception SQLException if a database access error occurs
   */
  public SQLWarning getWarnings() throws SQLException
  {
    return null;	// We handle warnings as errors
  }
  
  /**
   * After this call, getWarnings returns null until a new warning
   * is reported for this connection.
   *
   * @exception SQLException if a database access error occurs
   */
  public void clearWarnings() throws SQLException
  {
    // Not handles since we handle wanrings as errors
  }
  
  // **********************************************************
  //		END OF PUBLIC INTERFACE
  // **********************************************************
  
  /**
   * Send a query to the backend.  Returns one of the ResultSet
   * objects.
   *
   * <B>Note:</B> there does not seem to be any method currently
   * in existance to return the update count.
   *
   * @param sql the SQL statement to be executed
   * @return a ResultSet holding the results
   * @exception SQLException if a database error occurs
   */
  public synchronized ResultSet ExecSQL(String sql) throws SQLException
  {
    Field[] fields = null;
    Vector tuples = new Vector();
    byte[] buf = new byte[sql.length()];
    int fqp = 0;
    boolean hfr = false;
    String recv_status = null, msg;
    SQLException final_error = null;
    
    if (sql.length() > 8192)
      throw new SQLException("SQL Statement too long: " + sql);
    try
      {
	pg_stream.SendChar('Q');
	buf = sql.getBytes();
	pg_stream.Send(buf);
	pg_stream.SendChar(0);
      } catch (IOException e) {
	throw new SQLException("I/O Error: " + e.toString());
      }
      
      while (!hfr || fqp > 0)
	{
	  int c = pg_stream.ReceiveChar();
	  
	  switch (c)
	    {
	    case 'A':	// Asynchronous Notify
	      int pid = pg_stream.ReceiveInteger(4);
	      msg = pg_stream.ReceiveString(8192);
	      break;
	    case 'B':	// Binary Data Transfer
	      if (fields == null)
		throw new SQLException("Tuple received before MetaData");
	      tuples.addElement(pg_stream.ReceiveTuple(fields.length, true));
	      break;
	    case 'C':	// Command Status
	      recv_status = pg_stream.ReceiveString(8192);
	      if (fields != null)
		hfr = true;
	      else
		{
		  try
		    {
		      pg_stream.SendChar('Q');
		      pg_stream.SendChar(' ');
		      pg_stream.SendChar(0);
		    } catch (IOException e) {
		      throw new SQLException("I/O Error: " + e.toString());
		    }
		    fqp++;
		}
	      break;
	    case 'D':	// Text Data Transfer
	      if (fields == null)
		throw new SQLException("Tuple received before MetaData");
	      tuples.addElement(pg_stream.ReceiveTuple(fields.length, false));
	      break;
	    case 'E':	// Error Message
	      msg = pg_stream.ReceiveString(4096);
	      final_error = new SQLException(msg);
	      hfr = true;
	      break;
	    case 'I':	// Empty Query
	      int t = pg_stream.ReceiveChar();
	      
	      if (t != 0)
		throw new SQLException("Garbled Data");
	      if (fqp > 0)
		fqp--;
	      if (fqp == 0)
		hfr = true;
	      break;
	    case 'N':	// Error Notification
	      msg = pg_stream.ReceiveString(4096);
	      PrintStream log = DriverManager.getLogStream();
	      log.println(msg);
	      break;
	    case 'P':	// Portal Name
	      String pname = pg_stream.ReceiveString(8192);
	      break;
	    case 'T':	// MetaData Field Description
	      if (fields != null)
		throw new SQLException("Cannot handle multiple result groups");
	      fields = ReceiveFields();
	      break;
	    default:
	      throw new SQLException("Unknown Response Type: " + (char)c);
	    }
	}
      if (final_error != null)
	throw final_error;
      return new ResultSet(this, fields, tuples, recv_status, 1);
  }
  
  /**
   * Receive the field descriptions from the back end
   *
   * @return an array of the Field object describing the fields
   * @exception SQLException if a database error occurs
   */
  private Field[] ReceiveFields() throws SQLException
  {
    int nf = pg_stream.ReceiveInteger(2), i;
    Field[] fields = new Field[nf];
    
    for (i = 0 ; i < nf ; ++i)
      {
	String typname = pg_stream.ReceiveString(8192);
	int typid = pg_stream.ReceiveInteger(4);
	int typlen = pg_stream.ReceiveInteger(2);
	fields[i] = new Field(this, typname, typid, typlen);
      }
    return fields;
  }
  
  /**
   * In SQL, a result table can be retrieved through a cursor that
   * is named.  The current row of a result can be updated or deleted
   * using a positioned update/delete statement that references the
   * cursor name.
   *
   * We support one cursor per connection.
   *
   * setCursorName sets the cursor name.
   *
   * @param cursor the cursor name
   * @exception SQLException if a database access error occurs
   */
  public void setCursorName(String cursor) throws SQLException
  {
    this.cursor = cursor;
  }
  
  /**
   * getCursorName gets the cursor name.
   *
   * @return the current cursor name
   * @exception SQLException if a database access error occurs
   */
  public String getCursorName() throws SQLException
  {
    return cursor;
  }
  
  /**
   * We are required to bring back certain information by
   * the DatabaseMetaData class.  These functions do that.
   *
   * Method getURL() brings back the URL (good job we saved it)
   *
   * @return the url
   * @exception SQLException just in case...
   */
  public String getURL() throws SQLException
  {
    return this_url;
  }
  
  /**
   * Method getUserName() brings back the User Name (again, we
   * saved it)
   *
   * @return the user name
   * @exception SQLException just in case...
   */
  public String getUserName() throws SQLException
  {
    return PG_USER;
  }
  
  /**
   * This method is not part of the Connection interface. Its is an extension
   * that allows access to the PostgreSQL Large Object API
   *
   * @return PGlobj class that implements the API
   */
  public PGlobj getLargeObjectAPI() throws SQLException
  {
    return new PGlobj(this);
  }
}

// ***********************************************************************