textfile.java

有关JDBC的使用一些编程实例,有关与数据库连接的代码

/*
 *
 * textFile - an extension of tinySQL for text file access
 *
 * 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.util.*;
import java.lang.*;
import java.io.*;

public class textFile extends tinySQL {

  // the data directory where textFile stores its files
  //
  static String dataDir = System.getProperty("user.home") + "/.tinySQL";

  /**
   *
   * Creates a table given the name and a vector of
   * column definition arrays.
   * The column definition arrays have the following elements:
   *
   * Element 1: Data type
   * Element 2: Column name
   * Element 3: Size
   *
   * @param table_name the name of the table
   * @param v a Vector containing arrays of column definitions.
   * @see tinySQL#CreateTable
   *
   */
  void CreateTable ( String table_name, Vector v ) 
    throws IOException, tinySQLException {

    // make the data directory, if it needs to be make
    //
    mkDataDirectory();

    // perform an implicit drop table.
    //
    DropTable(table_name);

    // create the table definition file
    //
    FileOutputStream fdef = 
       new FileOutputStream( dataDir + "/" + table_name + ".def" );

    // open it as a DataOutputStream
    //
    DataOutputStream def = new DataOutputStream (fdef);

    // write out the column definition for the _DELETED column
    //
    def.writeBytes("CHAR|_DELETED|1\n");

    // write out the rest of the columns' definition. The
    // definition consists of datatype, column name, and
    // size delimited by a pipe symbol
    //
    for (int i = 0; i < v.size(); i++) {
       def.writeBytes( ((String[]) v.elementAt(i))[0] + "|");
       def.writeBytes( ((String[]) v.elementAt(i))[1] + "|");
       def.writeBytes( ((String[]) v.elementAt(i))[2] + "\n");
    }

    // flush the DataOutputStream and jiggle the handle
    //
    def.flush();

    // close the file
    //
    fdef.close();
  }

  /**
   *
   * Return a tinySQLTable object, given a table name.
   *
   * @param table_name
   * @see tinySQL#getTable
   *
   */
  tinySQLTable getTable (String table_name) throws tinySQLException {
    return (tinySQLTable) new textFileTable (dataDir, table_name);
  }

  /**
   *
   * Drop a named table by deleting it and its associated
   * .def file.
   *
   * @param fname table name
   * @see tinySQL#DropTable
   *
   */
  void DropTable (String fname) throws tinySQLException {

    try {

      delFile(fname);
      delFile(fname + ".def");

    } catch (Exception e) {
      throw new tinySQLException(e.getMessage());
    }

  } 


  /*
   *
   * Make the data directory unless it already exists
   *
   */
  void mkDataDirectory() throws NullPointerException {
  
    File dd = new File( dataDir );

    if (!dd.exists()) {
      dd.mkdir();
    }

  }

  /*
   *
   * Delete a file in the data directory
   *
   */
  void delFile (String fname) throws NullPointerException, IOException {

    File f = new File( dataDir + "/" + fname );

    // only delete a file that exists
    //
    if (f.exists()) {

      // try the delete. If it fails, complain
      //
      if (!f.delete()) {
        throw new IOException("Could not delete file: " + 
                               dataDir + "/" + fname + ".");
      }

    }

  }

  /*
   * regression test
   */
  public static void main(String argv[]) {
    textFile foo = new textFile();
    tsResultSet trs = null; 
    try {
      trs = foo.sqlexec("CREATE TABLE test (name CHAR(10))");
      trs = foo.sqlexec("INSERT INTO test (name) VALUES('test')");
      trs = foo.sqlexec("SELECT name FROM test");
    } catch (Exception e) {
      e.printStackTrace();
    }

    tsRow row = trs.rowAt(0);

    tsColumn column = trs.columnAtIndex(0);
    String colval     = row.columnAsString(column);

    if (colval.startsWith("test")) {
      System.out.println("textFile driver installed correctly.");
    } else {
      System.out.println("Test was not successful :-(");
      System.out.println("Got \"" + colval + "\", expected \"test\"");
    }

  }
}