jdbcstatement.java

一个可以在applet窗体上持行sql语句并显示返回结果的程序

   * @see #getResultSet
   * @see #getUpdateCount
   * @see #getMoreResults
   */
  public boolean execute(String sql) throws SQLException {
    if(Trace.TRACE) Trace.trace();
    fetchResult(sql);
    if(rSet==null) {
      return false;
    }
    return rSet.isResult();
  }
  /**
   *  Returns the current result as a <code>ResultSet</code> object.
   *  This method should be called only once per result.
   *
   * @return the current result as a ResultSet; null if the result
   * is an update count or there are no more results
   * @see #execute
   */
  public ResultSet getResultSet() {
    if(Trace.TRACE) Trace.trace();
    return rSet;
  }
  /**
   *  Returns the current result as an update count;
   *  if the result is a ResultSet or there are no more results, -1
   *  is returned.
   *  This method should be called only once per result.
   *
   * @return the current result as an update count; -1 if it is a
   * ResultSet or there are no more results
   * @see #execute
   */
  public int getUpdateCount() {
    if(rSet==null) {
      return -1;
    }
    return rSet.getUpdateCount();
  }
  /**
   * Moves to a Statement's next result.  It returns true if
   * this result is a ResultSet.  This method also implicitly
   * closes any current ResultSet obtained with getResultSet.
   *
   * There are no more results when (!getMoreResults() &&
   * (getUpdateCount() == -1)
   * <P><font color="#009900">
   * Hypersonic SQL currently does not support multiple ResultSets.
   * </font><P>
   * @return true if the next result is a ResultSet; false if it is
   * an update count or there are no more results
   * @see #execute
   */
  public boolean getMoreResults() {
    if(Trace.TRACE) Trace.trace();
    return false;
  }
  /**
   * JDBC 2.0
   *
   * Gives the driver a hint as to the direction in which
	 * the rows in a result set
   * will be processed. The hint applies only to result sets created
   * using this Statement object.  The default value is
   * ResultSet.FETCH_FORWARD.
   * <p>Note that this method sets the default fetch direction for
	 * result sets generated by this <code>Statement</code> object.
	 * Each result set has its own methods for getting and setting
	 * its own fetch direction.
   * @param direction the initial direction for processing rows
   * @exception SQLException if a database access error occurs
	 * or the given direction
   * is not one of ResultSet.FETCH_FORWARD, ResultSet.FETCH_REVERSE, or
   * ResultSet.FETCH_UNKNOWN
   */
//#ifdef JAVA2
  public void setFetchDirection(int direction) throws SQLException {
    if(Trace.TRACE) Trace.trace();
    if(direction!=ResultSet.FETCH_FORWARD) {
      throw Trace.error(Trace.FUNCTION_NOT_SUPPORTED);
    }
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Retrieves the direction for fetching rows from
	 * database tables that is the default for result sets
	 * generated from this <code>Statement</code> object.
	 * If this <code>Statement</code> object has not set
	 * a fetch direction by calling the method <code>setFetchDirection</code>,
	 * the return value is implementation-specific.
   *
   * @return the default fetch direction for result sets generated
	 *          from this <code>Statement</code> object
   */
//#ifdef JAVA2
  public int getFetchDirection() {
    if(Trace.TRACE) Trace.trace();
    return ResultSet.FETCH_FORWARD;
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Gives the JDBC driver a hint as to the number of rows that should
   * be fetched from the database when more rows are needed.  The number
   * of rows specified affects only result sets created using this
   * statement. If the value specified is zero, then the hint is ignored.
   * The default value is zero.
   *
   * @param rows the number of rows to fetch
   * condition 0 <= rows <= this.getMaxRows() is not satisfied.
   */
//#ifdef JAVA2
  public void setFetchSize(int rows) {
    if(Trace.TRACE) Trace.trace();
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Retrieves the number of result set rows that is the default
	 * fetch size for result sets
	 * generated from this <code>Statement</code> object.
	 * If this <code>Statement</code> object has not set
	 * a fetch size by calling the method <code>setFetchSize</code>,
	 * the return value is implementation-specific.
   * @return the default fetch size for result sets generated
	 *          from this <code>Statement</code> object
   */
//#ifdef JAVA2
  public int getFetchSize() {
    if(Trace.TRACE) Trace.trace();
    return 1;
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Retrieves the result set concurrency.
   */
//#ifdef JAVA2
  public int getResultSetConcurrency() {
    if(Trace.TRACE) Trace.trace();
    return ResultSet.CONCUR_READ_ONLY;
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Determine the result set type.
   */
//#ifdef JAVA2
  public int getResultSetType() {
    if(Trace.TRACE) Trace.trace();
    return ResultSet.TYPE_FORWARD_ONLY;
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Adds a SQL command to the current batch of commmands for the statement.
   * This method is optional.
   * <P><font color="#009900">
   * Hypersonic SQL currently does not support this feature because there is
   * no performance win in using batches.
   * </font><P>
   * @param sql typically this is a static SQL INSERT or UPDATE statement
   * @exception SQLException if a database access error occurs, or the
   * driver does not support batch statements
   */
//#ifdef JAVA2
  public void addBatch(String sql) throws SQLException {
    if(Trace.TRACE) Trace.trace();
    // todo
    throw Trace.error(Trace.FUNCTION_NOT_SUPPORTED);
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Makes the set of commands in the current batch empty.
   * This method is optional.
   *
   * @exception SQLException if a database access error occurs or the
   * driver does not support batch statements
   */
//#ifdef JAVA2
  public void clearBatch() throws SQLException {
    if(Trace.TRACE) Trace.trace();
    throw Trace.error(Trace.FUNCTION_NOT_SUPPORTED);
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Submits a batch of commands to the database for execution.
   * This method is optional.
   *
   * @return an array of update counts containing one element for each
   * command in the batch.  The array is ordered according
   * to the order in which commands were inserted into the batch.
   * @exception SQLException if a database access error occurs or the
   * driver does not support batch statements
   */
//#ifdef JAVA2
  public int[] executeBatch() throws SQLException {
    if(Trace.TRACE) Trace.trace();
    // todo
    throw Trace.error(Trace.FUNCTION_NOT_SUPPORTED);
  }
//#endif JAVA2
  /**
   * JDBC 2.0
   *
   * Returns the <code>Connection</code> object
	 * that produced this <code>Statement</code> object.
	 * @return the connection that produced this statement
   */
//#ifdef JAVA2
  public Connection getConnection() {
    if(Trace.TRACE) Trace.trace();
    return cConnection;
  }
//#endif JAVA2

  jdbcStatement(jdbcConnection c) {
    bEscapeProcessing=true;
    cConnection=c;
  }
  private void fetchResult(String sql) throws SQLException {
    if(bEscapeProcessing) {
      sql=cConnection.nativeSQL(sql);
    }
    closeOldResult();
    if(iMaxRows==0) {
      rSet=cConnection.execute(sql);
    } else {
      try {
        sql="SET MAXROWS "+iMaxRows+";"+sql;
        rSet=cConnection.execute(sql);
        cConnection.execute("SET MAXROWS 0");
      } catch(SQLException e) {
        cConnection.execute("SET MAXROWS 0");
        throw e;
      }
    }
  }
  private void closeOldResult() {
    // this is necessary to conform the JDBC standard
    if(rSet!=null) {
      rSet.close();
      rSet=null;
    }
  }
}