tinysqlresultsetmetadata.java

有关JDBC的使用一些编程实例,有关与数据库连接的代码

/**
 * This is the tinySQL Result Set Meta Data class.
 *
 * A lot of this code is based on or directly taken from
 * George Reese's ([e-mail]) mSQL driver.
 *
 * So, it's probably safe to say:
 *
 * Portions of this code Copyright (c) 1996 George Reese
 *
 * The rest of it:
 *
 * Copyright 1996, Brian C. Jepson
 *                 ([e-mail])
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

import java.sql.SQLException;
import java.sql.Types;

public class tinySQLResultSetMetaData implements java.sql.ResultSetMetaData {

  /**
   *
   * The result set.
   *
   */
  private tsResultSet tsql;

  /**
   *
   * Constructs a tinySQLResultSet; requires a tsResultSet object
   * @param result the tsResultSet object
   *
   */
  public tinySQLResultSetMetaData(tsResultSet result) {
    tsql = result;
  }
  
  /**
   *
   * Returns the number of columns in this result set.
   * @see java.sqlResultSetMetaData#getColumnCount
   * @return number of columns
   *
   */
  public int getColumnCount() throws SQLException {
    return tsql.numcols();
  }

  /**
   *
   * Is the column an autoincrement (identity, counter) column?
   * @see java.sql.ResultSetMetaData#isAutoIncrement
   * @return false - tinySQL does not support autoincrement columns
   *
   */
  public boolean isAutoIncrement(int column) throws SQLException { 
    return false;
  }

  /**
   *
   * Is case significant in column names?
   * @see java.sql.ResultSetMetaData#isCaseSensitive
   * @return true
   *
   */
  public boolean isCaseSensitive(int column) throws SQLException {
    return true;
  }

  /**
   *
   * Can the column be used in a where clause?
   * @see java.sql.ResultSetMetaData#isSearchable
   * @return 
   *
   */
  public boolean isSearchable(int column) throws SQLException {
    return true;
  }

  /**
   *
   * Is the column some sort of currency?
   * @see java.sql.ResultSetMetaData#isCurrency
   * @return tinySQL doesn't have such things, so it's false
   *
   */
  public boolean isCurrency(int column) throws SQLException {
    return false;
  }

  /**
   *
   * Determines if the column in question is nullable. tinySQL
   * does not yet support nulls.
   * @see java.sql.ResultSetMetaData#isNullable
   * @return columnNoNulls, columnNullable, or columnNullableUnknown
   *
   */
  public int isNullable(int column) throws SQLException{
    return columnNoNulls;
  }

  /**
   *
   * All tinySQL integers are signed, so this returns true.
   * @see java.sql.ResultSetMetaData#isSigned
   * @return true
   *
   */
  public boolean isSigned(int column) throws SQLException {
    return true;
  }

  /**
   *
   * Gives the display size for this column.
   * @see java.sql.ResultSetMetaData#getColumnDisplaySize
   *
   */
  public int getColumnDisplaySize(int column) throws SQLException {

    // get a column object. Remember, tinySQL uses a column
    // offset of zero, but JDBC columns start numbering at one.
    // That's why there's a -1 in the columnAtIndex invocation.
    //
    tsColumn col = tsql.columnAtIndex(column-1);
    return col.size;

  }

  /**
   *
   * This returns the column name in the form table_name.column_name.
   * @see java.sql.ResultSetMetaData#getColumnLabel
   * @param column the column whose label is wanted
   * @return the fully qualified column name
   *
   */
  public String getColumnLabel(int column)
       throws SQLException {

    // get the column, return its table and name, separated by a '.'
    //
    tsColumn col = tsql.columnAtIndex(column-1);
    return (col.table + "." + col.name);
  }

  /**
   * The name of a given column
   * @see java.sql.ResultSetMetaData#getColumnName
   * @param column the column whose name is wanted
   * @return the name of the requested column
   */
  public String getColumnName(int column)
       throws SQLException {

    // get the column and return its name
    //
    tsColumn col = tsql.columnAtIndex(column-1);
    return col.name;
  }

  /**
   *
   * What's the column's schema? This is not applicable to tinySQL,
   * so it returns an empty string.
   *
   */
  public String getSchemaName(int column)
       throws SQLException {
    return "";
  }

  /**
   * 
   * What's the column's precision? This is also not supported by
   * tinySQL.
   *
   */
  public int getPrecision(int column)
       throws SQLException {
    throw new SQLException("tinySQL does not support precision.");
  }

  /**
   *
   * What's a column's number of digits to right of decimal? Yet
   * another fine feature *not* supported by tinySQL.
   *
   */
  public int getScale(int column) throws SQLException {
    throw new SQLException("tinySQL does not support scale.");
  }

  /**
   *
   * Gives the name of the table to which this column belongs.
   * @see java.sql.ResultSetMetaData#getTableName
   * @param column the column of the field this information is needed for
   * @return the table name
   *
   */
  public String getTableName(int column)
       throws SQLException {

    // retrieve the column info and return the table name
    //
    tsColumn col = tsql.columnAtIndex(column-1);
    return col.table;
  }

  /**
   * 
   * Return the column's table catalog name. Not supported by tinySQL
   * 
   */
  public String getCatalogName(int column)
       throws SQLException {
    throw new SQLException("tinySQL does not support catalogues.");
  }

  /**
   *
   * Gives the column type using the types in java.sql.Types.
   * @see java.sqlTypes
   * @see java.sql.ResultSetMetaData#getColumnType
   * @exception SQLException thrown for any number of reasons
   * @param column the column type information is needed on
   * @return the type as listed in java.sql.Types
   *
   */
  public int getColumnType(int column) throws SQLException {
    
    // get the column info object
    //
    tsColumn col = tsql.columnAtIndex(column-1);
  
    // report on either of these two types
    //
    if (col.type.equals("CHAR")) {
      return Types.CHAR;
    }
    if (col.type.equals("NUMERIC")) {
      return Types.INTEGER;
    }
    
    throw new SQLException("Unknown data type.");
  }

  /**
   *
   * Gives the column type as a string.
   * @see java.sql.ResultSetMetaData#getColumnTypeName
   * @exception SQLException thrown at you
   * @param column the column for which the type name is wanted
   * @return the name of the column type
   *
   */
  public String getColumnTypeName(int column)
       throws SQLException {

    // just call getColumnType, and report on what it said
    //
    switch(getColumnType(column)) {

    case Types.INTEGER:
      return "INT";

    case Types.CHAR:
      return "CHAR";

    default:
      return "NULL";
    }
  }

  /**
   *
   * Is the column definitely not writable? This has no meaning
   * in tinySQL
   *
   */
  public boolean isReadOnly(int column) throws SQLException {
    return false;
  }

  /**
   *
   * Is the column potentially writable? This has no meaning
   * in tinySQL
   *
   */
  public boolean isWritable(int column) throws SQLException {
    return true;
  }

  /**
   *
   * Is the column definitely writable? This has no meaning
   * in tinySQL
   *
   */
  public boolean isDefinitelyWritable(int column) throws SQLException {
    return true;
  }

}