database.java

数据连接池,希望广大操作系统研究者广泛利用

/*
 * Copyright (c) 1998-2001 Caucho Technology -- all rights reserved
 *
 * Caucho Technology permits redistribution, modification and use
 * of this file in source and binary form ("the Software") under the
 * Caucho Developer Source License ("the License").  The following
 * conditions must be met:
 *
 * 1. Each copy or derived work of the Software must preserve the copyright
 *    notice and this notice unmodified.
 *
 * 2. Redistributions of the Software in source or binary form must include 
 *    an unmodified copy of the License, normally in a plain ASCII text
 *
 * 3. The names "Resin" or "Caucho" are trademarks of Caucho Technology and
 *    may not be used to endorse products derived from this software.
 *    "Resin" or "Caucho" may not appear in the names of products derived
 *    from this software.
 *
 * 4. Caucho Technology requests that attribution be given to Resin
 *    in any manner possible.  We suggest using the "Resin Powered"
 *    button or creating a "powered by Resin(tm)" link to
 *    http://www.caucho.com for each page served by Resin.
 *
 * This Software is provided "AS IS," without a warranty of any kind. 
 * ALL EXPRESS OR IMPLIED REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
 * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED.
 *
 * CAUCHO TECHNOLOGY AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE OR ANY THIRD PARTY AS A RESULT OF USING OR
 * DISTRIBUTING SOFTWARE. IN NO EVENT WILL CAUCHO OR ITS LICENSORS BE LIABLE
 * FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
 * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
 * INABILITY TO USE SOFTWARE, EVEN IF HE HAS BEEN ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGES.      
 *
 * @author Scott Ferguson
 */

package com.caucho.jslib;

import java.io.*;
import java.sql.*;
import java.util.*;

import javax.sql.*;
import javax.naming.*;

import com.caucho.util.*;

/**
 * Encapsulates a database connection for JavaScript.
 *
 * <code><pre>
 * var conn = new Database("jdbc/test");
 * var rs = conn.query("select NAME from HOUSES");
 *
 * while (rs.next())
 *   out.writeln(rs.get(1) + "&lt;br/>");
 *
 * conn.close();
 * </pre></code>
 */
public class Database {
  private DataSource dataSource;
  private Connection conn;
  private Statement stmt;
  private ResultSet rs;

  /**
   * Creates a new database looking up the DataSource in JNDI.
   *
   * @param name jndi name to the data source
   */
  public Database(String name)
    throws Exception
  {
    InitialContext cxt = null;

    try {
      cxt = new InitialContext();
    } catch (Exception e) {
    }
    
    try {
      if (cxt != null)
        dataSource = (DataSource) cxt.lookup(name);
    } catch (Exception e) {
    }

    try {
      if (dataSource == null && cxt != null)
        dataSource = (DataSource) cxt.lookup("java:comp/env/" + name);
    } catch (Exception e) {
    }

    try {
      if (dataSource != null && cxt != null)
        dataSource = (DataSource) cxt.lookup("java:comp/env/jdbc/" + name);
    } catch (Exception e) {
    }

    if (dataSource == null)
      dataSource = com.caucho.sql.DBPool.getPool(name);

    if (dataSource == null)
      throw new SQLException("no data source: " + name);

    // Automatically reclaim the database when the script ends
    Exit.addExit(exitHandler, this);
  }

  /**
   * Execute the sql as a query.
   */
  public ResultSet query(String sql)
    throws SQLException
  {
    if (rs != null) {
      ResultSet rs = this.rs;
      this.rs = null;
      rs.close();
    }
    
    Statement stmt = getStatement();

    rs = stmt.executeQuery(sql);

    return rs;
  }

  /**
   * Execute the sql as a query.
   */
  public int update(String sql)
    throws SQLException
  {
    if (rs != null) {
      ResultSet rs = this.rs;
      this.rs = null;
      rs.close();
    }
    
    Statement stmt = getStatement();

    return stmt.executeUpdate(sql);
  }

  /**
   * Returns the JDBC DataSource.  Applications that
   * need direct access to the data source.
   */
  public DataSource getDataSource()
    throws SQLException
  {
    return dataSource;
  }

  /**
   * Returns the JDBC Connection for the database.  Applications that need
   * direct access to the Connection can use this.
   */
  public Connection getConnection()
    throws SQLException
  {
    if (conn == null)
      conn = dataSource.getConnection();

    return conn;
  }

  /**
   * Returns the JDBC Statement for the database.  Applications that
   * need direct access to the Java Statement can use this.
   */
  public Statement getStatement()
    throws SQLException
  {
    if (stmt == null) {
      Connection conn = getConnection();
    
      stmt = conn.createStatement();
    }

    return stmt;
  }

  /**
   * Close the connection.  Automatically closes the ResultSet, Statement
   * and Connection.
   */
  public void close()
    throws SQLException
  {
    try {
      if (rs != null) {
        ResultSet rs = this.rs;
        this.rs = null;
        rs.close();
      }
      
      if (stmt != null) {
        Statement stmt = this.stmt;
        this.stmt = null;
        stmt.close();
      }
    } finally {
      if (conn != null) {
        Connection conn = this.conn;
        this.conn = null;
        conn.close();
      }
    }
  }

  /**
   * Listens for the exit event.  When Database is used in JavaScript,
   * the database will be automatically closed on exit.
   */
  private static ExitListener exitHandler = new ExitListener() {
    public void handleExit(Object o)
    {
      Database db = (Database) o;

      try {
	db.close();
      } catch (SQLException e) {
      }
    }
  };
}