//文件：DbConnectionManager.java
package com.qingtuo.db.pool;
import java.sql.*;
import java.io.*;
import java.util.*;
/**
* Central manager of database connections.
*/
public class DbConnectionManager {
private static DbConnectionProvider connectionProvider;
private static Object providerLock = new Object();
/**
* Returns a database connection from the currently active connection
* provider.
*/
public static Connection getConnection() {
if (connectionProvider == null) {
synchronized (providerLock) {
if (connectionProvider == null) {
//Create the connection provider -- for now, this is hardcoded. For
//the next beta, I'll change this to load up the provider dynamically.
connectionProvider = new DbConnectionDefaultPool();
connectionProvider.start();
}
}
}
Connection con = connectionProvider.getConnection();
if (con == null) {
System.err.println("WARNING: DbConnectionManager.getConnection() failed to obtain a connection.");
}
return con;
}
/**
* Returns the current connection provider. The only case in which this
* method should be called is if more information about the current
* connection provider is needed. Database connections should always be
* obtained by calling the getConnection method of this class.
*/
public static DbConnectionProvider getDbConnectionProvider() {
return connectionProvider;
}
/**
* Sets the connection provider. The old provider (if it exists) is shut
* down before the new one is started. A connection provider should
* not be started before being passed to the connection manager.
*/
public static void setDbConnectionProvider(DbConnectionProvider provider) {
synchronized (providerLock) {
if (connectionProvider != null) {
connectionProvider.destroy();
connectionProvider = null;
}
connectionProvider = provider;
provider.start();
}
}
}