dbconnectionmanager.java

基于Jabber协议的即时消息服务器

/**
 * $RCSfile$
 * $Revision: 4263 $
 * $Date: 2006-07-05 14:44:36 -0700 (Wed, 05 Jul 2006) $
 *
 * Copyright (C) 2004 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution.
 */

package org.jivesoftware.database;

import org.jivesoftware.util.ClassUtils;
import org.jivesoftware.util.JiveGlobals;
import org.jivesoftware.util.Log;

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

/**
 * Central manager of database connections. All methods are static so that they
 * can be easily accessed throughout the classes in the database package.<p>
 *
 * This class also provides a set of utility methods that abstract out
 * operations that may not work on all databases such as setting the max number
 * or rows that a query should return.
 *
 * @author Jive Software
 * @see ConnectionProvider
 */
public class DbConnectionManager {

    private static ConnectionProvider connectionProvider;
    private static final Object providerLock = new Object();

    // True if connection profiling is turned on. Always false by default.
    private static boolean profilingEnabled = false;

    // True if the database support transactions.
    private static boolean transactionsSupported;
    // True if the database requires large text fields to be streamed.
    private static boolean streamTextRequired;
    // True if the database supports the Statement.setMaxRows() method.
    private static boolean maxRowsSupported;
    // True if the database supports the Statement.setFetchSize() method.
    private static boolean fetchSizeSupported;
    // True if the database supports correlated subqueries.
    private static boolean subqueriesSupported;
    // True if the database supports scroll-insensitive results.
    private static boolean scrollResultsSupported;
    // True if the database supports batch updates.
    private static boolean batchUpdatesSupported;

    private static DatabaseType databaseType = DatabaseType.unknown;

    private static SchemaManager schemaManager = new SchemaManager();

    /**
     * Returns a database connection from the currently active connection
     * provider. (auto commit is set to true).
     */
    public static Connection getConnection() throws SQLException {
        if (connectionProvider == null) {
            synchronized (providerLock) {
                if (connectionProvider == null) {
                    // Attempt to load the connection provider classname as
                    // a Jive property.
                    String className = JiveGlobals.getXMLProperty("connectionProvider.className");
                    if (className != null) {
                        // Attempt to load the class.
                        try {
                            Class conClass = ClassUtils.forName(className);
                            setConnectionProvider((ConnectionProvider)conClass.newInstance());
                        }
                        catch (Exception e) {
                            Log.error("Warning: failed to create the " +
                                    "connection provider specified by connection" +
                                    "Provider.className. Using the default pool.", e);
                            setConnectionProvider(new DefaultConnectionProvider());
                        }
                    }
                    else {
                        setConnectionProvider(new DefaultConnectionProvider());
                    }
                }
            }
        }
        Connection con = connectionProvider.getConnection();

        if (con == null) {
            Log.error("WARNING: ConnectionManager.getConnection() " +
                    "failed to obtain a connection.");
        }
        // See if profiling is enabled. If yes, wrap the connection with a
        // profiled connection.
        if (profilingEnabled) {
            return new ProfiledConnection(con);
        }
        else {
            return con;
        }
    }

    /**
     * Returns a Connection from the currently active connection provider that
     * is ready to participate in transactions (auto commit is set to false).
     */
    public static Connection getTransactionConnection() throws SQLException {
        Connection con = getConnection();
        if (isTransactionsSupported()) {
            con.setAutoCommit(false);
        }
        return con;
    }

    /**
     * Closes a PreparedStatement and Connection. However, it first rolls back the transaction or
     * commits it depending on the value of <code>abortTransaction</code>.
     */
    public static void closeTransactionConnection(PreparedStatement pstmt, Connection con,
            boolean abortTransaction)
    {
        try {
            if (pstmt != null) {
                pstmt.close();
            }
        }
        catch (Exception e) {
            Log.error(e);
        }
        closeTransactionConnection(con, abortTransaction);
    }

    /**
     * Closes a Connection. However, it first rolls back the transaction or
     * commits it depending on the value of <code>abortTransaction</code>.
     */
    public static void closeTransactionConnection(Connection con, boolean abortTransaction) {
        // test to see if the connection passed in is null
        if (con == null) {
            return;
        }

        // Rollback or commit the transaction
        if (isTransactionsSupported()) {
            try {
                if (abortTransaction) {
                    con.rollback();
                }
                else {
                    con.commit();
                }
            }
            catch (Exception e) {
                Log.error(e);
            }
        }
        try {
            // Reset the connection to auto-commit mode.
            if (isTransactionsSupported()) {
                con.setAutoCommit(true);
            }
        }
        catch (Exception e) {
            Log.error(e);
        }
        try {
            // Close the db connection.
            con.close();
        }
        catch (Exception e) {
            Log.error(e);
        }
    }

    /**
     * Closes a result set. This method should be called within the finally section of
     * your database logic, as in the following example:
     *
     * <pre>
     *  public void doSomething(Connection con) {
     *      ResultSet rs = null;
     *      PreparedStatement pstmt = null;
     *      try {
     *          pstmt = con.prepareStatement("select * from blah");
     *          rs = pstmt.executeQuery();
     *          ....
     *      }
     *      catch (SQLException sqle) {
     *          Log.error(sqle);
     *      }
     *      finally {
     *          ConnectionManager.closeResultSet(rs);
     *          ConnectionManager.closePreparedStatement(pstmt);
     *      }
     * } </pre>
     */
    public static void closeResultSet(ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
        }
        catch (SQLException e) {
            Log.error(e);
        }
    }

    /**
     * Closes a statement. This method should be called within the finally section of
     * your database logic, as in the following example:
     *
     * <pre>
     *  public void doSomething(Connection con) {
     *      PreparedStatement pstmt = null;
     *      try {
     *          pstmt = con.prepareStatement("select * from blah");
     *          ....
     *      }
     *      catch (SQLException sqle) {
     *          Log.error(sqle);
     *      }
     *      finally {
     *          ConnectionManager.closePreparedStatement(pstmt);
     *      }
     * } </pre>
     *
     * @param stmt the statement.
     */
    public static void closeStatement(Statement stmt) {
        try {
            if (stmt != null) {
                stmt.close();
            }
        }
        catch (Exception e) {
            Log.error(e);
        }
    }

    /**
     * Closes a result set, statement and database connection (returning the connection to
     * the connection pool). This method should be called within the finally section of
     * your database logic, as in the following example:
     *
     * <pre>
     * Connection con = null;
     * PrepatedStatment pstmt = null;
     * ResultSet rs = null;
     * try {
     *     con = ConnectionManager.getConnection();
     *     pstmt = con.prepareStatement("select * from blah");
     *     rs = psmt.executeQuery();
     *     ....
     * }
     * catch (SQLException sqle) {
     *     Log.error(sqle);
     * }
     * finally {
     *     ConnectionManager.closeConnection(rs, pstmt, con);
     * }</pre>
     *
     * @param stmt the statement.
     * @param con the connection.
     */
    public static void closeConnection(ResultSet rs, Statement stmt, Connection con) {
        closeResultSet(rs);
        closeStatement(stmt);
        closeConnection(con);
    }

    /**
     * Closes a statement and database connection (returning the connection to
     * the connection pool). This method should be called within the finally section of
     * your database logic, as in the following example:
     * <p/>
     * <pre>
     * Connection con = null;
     * PrepatedStatment pstmt = null;
     * try {
     *     con = ConnectionManager.getConnection();
     *     pstmt = con.prepareStatement("select * from blah");
     *     ....
     * }
     * catch (SQLException sqle) {
     *     Log.error(sqle);
     * }
     * finally {
     *     DbConnectionManager.closeConnection(pstmt, con);
     * }</pre>
     *
     * @param stmt the statement.
     * @param con the connection.
     */
    public static void closeConnection(Statement stmt, Connection con) {
        try {
            if (stmt != null) {
                stmt.close();
            }
        }
        catch (Exception e) {
            Log.error(e);
        }
        closeConnection(con);
    }

    /**
     * Closes a database connection (returning the connection to the connection pool). Any
     * statements associated with the connection should be closed before calling this method.
     * This method should be called within the finally section of your database logic, as
     * in the following example:
     * <p/>
     * <pre>
     * Connection con = null;
     * try {
     *     con = ConnectionManager.getConnection();
     *     ....
     * }
     * catch (SQLException sqle) {
     *     Log.error(sqle);
     * }
     * finally {
     *     DbConnectionManager.closeConnection(con);
     * }</pre>
     *
     * @param con the connection.
     */
    public static void closeConnection(Connection con) {
        try {
            if (con != null) {
                con.close();
            }
        }
        catch (Exception e) {
            Log.error(e);
        }
    }

    /**
     * Creates a scroll insensitive Statement if the JDBC driver supports it, or a normal
     * Statement otherwise.
     *
     * @param con the database connection.
     * @return a Statement
     * @throws SQLException if an error occurs.
     */
    public static Statement createScrollableStatement(Connection con) throws SQLException {
        if (isScrollResultsSupported()) {
            return con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
        }
        else {
            return con.createStatement();
        }
    }

    /**
     * Creates a scroll insensitive PreparedStatement if the JDBC driver supports it, or a normal
     * PreparedStatement otherwise.
     *
     * @param con the database connection.
     * @param sql the SQL to create the PreparedStatement with.
     * @return a PreparedStatement
     * @throws java.sql.SQLException if an error occurs.
     */
    public static PreparedStatement createScrollablePreparedStatement(Connection con, String sql)
            throws SQLException {
        if (isScrollResultsSupported()) {
            return con.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
        }
        else {
            return con.prepareStatement(sql);
        }
    }

    /**
     * Scrolls forward in a result set the specified number of rows. If the JDBC driver
     * supports the feature, the cursor will be moved directly. Otherwise, we scroll
     * through results one by one manually by calling <tt>rs.next()</tt>.
     *
     * @param rs the ResultSet object to scroll.
     * @param rowNumber the row number to scroll forward to.
     * @throws SQLException if an error occurs.
     */
    public static void scrollResultSet(ResultSet rs, int rowNumber) throws SQLException {
        // If the driver supports scrollable result sets, use that feature.
        if (isScrollResultsSupported()) {
            if (rowNumber > 0) {
                rs.setFetchDirection(ResultSet.FETCH_FORWARD);

                // We will attempt to do a relative fetch. This may fail in SQL Server if
                // <resultset-navigation-strategy> is set to absolute. It would need to be
                // set to looping to work correctly.
                // If so, manually scroll to the correct row.
                try {
                    rs.relative(rowNumber);
                }
                catch (SQLException e) {
                    for (int i = 0; i < rowNumber; i++) {