Revision 1092
Added by Jing Tao almost 22 years ago
| src/edu/ucsb/nceas/metacat/DBConnectionPool.java | ||
|---|---|---|
| 42 | 42 |
* This a singleton class, this means only one instance of this class could |
| 43 | 43 |
* be in the program at one time. |
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*/ |
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public class DBConnectionPool |
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public class DBConnectionPool implements Runnable
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{
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|
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//static attributes |
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private static DBConnectionPool instance; |
| 50 | 50 |
private static Vector connectionPool; |
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private static Thread runner; |
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|
| 52 | 53 |
//maximum connection number in the connection pool |
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final static int MAXIMUMCONNECTIONNUMBER= |
| 54 | 55 |
Integer.parseInt(MetaCatUtil.getOption("maximumConnections"));
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|
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//inintila connection number int the connection pool |
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final static int INITIALCONNECTIONNUMBER= |
| 57 | 59 |
Integer.parseInt(MetaCatUtil.getOption("initialConnections"));
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|
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//the number to increase connection pool size |
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final static int INCREASECONNECTIONNUMBER= |
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Integer.parseInt(MetaCatUtil.getOption("incrementConnections"));
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//maximum age for a connection (in milli seconds) |
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final static long MAXIMUMAGE = |
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Long.parseLong(MetaCatUtil.getOption("maximumConnectionAge"));
|
| ... | ... | |
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* Returns the single instance, creating one if it's the |
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* first time this method is called. |
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*/ |
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static synchronized public DBConnectionPool getInstance()
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public static synchronized DBConnectionPool getInstance()
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throws SQLException |
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{
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MetaCatUtil.debugMessage |
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("MaximumConnectionNumber: "+MAXIMUMCONNECTIONNUMBER, 49);
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MetaCatUtil.debugMessage |
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("Intial connection number: "+INITIALCONNECTIONNUMBER, 49);
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MetaCatUtil.debugMessage |
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("Increated connection Number: "+INCREASECONNECTIONNUMBER, 49);
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MetaCatUtil.debugMessage |
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("Maximum connection age: "+MAXIMUMAGE, 49);
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MetaCatUtil.debugMessage |
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("Maximum connection time: "+MAXIMUMCONNECTIONTIME, 49);
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MetaCatUtil.debugMessage |
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("Maximum usage count: "+MAXIMUMUSAGENUMBER, 49);
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if (instance == null) |
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{
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instance = new DBConnectionPool(); |
| ... | ... | |
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return instance; |
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}//getInstance |
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/** |
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* Method to get the size of DBConnectionPool |
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*/ |
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public int getSizeOfDBConnectionPool() |
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{
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return connectionPool.size(); |
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} |
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/** |
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* This is a private constructor since it is singleton |
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*/ |
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private DBConnectionPool() throws SQLException |
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{
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connectionPool = new Vector(); |
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initialDBConnectionPool(); |
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//running the thread to recycle DBConnection |
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runner = new Thread(this); |
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runner.start(); |
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}//DBConnection |
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/** |
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* Method to get the size of DBConnectionPool |
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*/ |
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public int getSizeOfDBConnectionPool() |
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{
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return connectionPool.size(); |
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} |
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/** |
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* Method to initial a pool of DBConnection objects |
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*/ |
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private Vector initialDBConnectionPool() throws SQLException
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{
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private void initialDBConnectionPool() throws SQLException
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{
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DBConnection dbConn = null; |
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|
| ... | ... | |
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connectionPool.add(dbConn); |
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} |
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return connectionPool; |
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} |
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}//initialDBConnectionPool |
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/** |
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* Method to get Connection object (Not DBConnection) |
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*/ |
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/*public static Connection getConnection() throws SQLException |
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{
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DBConnection dbConn = null; |
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//get a DBConnection |
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dbConn = getDBConnection(); |
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//get connection object in DBConnection object |
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//The following getConnections method is in DBConnection class |
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return dbConn.getConnections(); |
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}*/ |
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/** |
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* Method to get a DBConnection in connection pool |
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* 1) try to get a DBConnection from DBConnection pool |
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* 2) if 1) failed, then check the size of pool. If the size reach the |
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* maximum number of connection, throw a exception: couldn't get one |
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* 3) If the size is less than the maximum number of connectio, create some |
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* new connections and recursive get one |
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*/ |
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public static DBConnection getDBConnection() throws SQLException |
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public static synchronized DBConnection getDBConnection() throws SQLException
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{
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DBConnection db = null; |
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DBConnection db = null; |
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MetaCatUtil.debugMessage("Try to checking out connection...", 10);
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//try every DBConnection in the pool |
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synchronized(connectionPool) |
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{
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for (int i=0; i<connectionPool.size(); i++) |
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{
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db = (DBConnection) connectionPool.elementAt(i); |
| ... | ... | |
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//If this connection is good, return this DBConnection |
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if (validateDBConnection(db)) |
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{
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//set this DBConnection status |
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db.setStatus(BUSY); |
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//increase one usageCount |
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db.increaseUsageCount(1); |
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//debug message |
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MetaCatUtil.debugMessage("The connection is checked out: "
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+db.getTag(), 5); |
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MetaCatUtil.debugMessage("The age is "+db.getAge(), 5);
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MetaCatUtil.debugMessage("The usage is "+db.getUsageCount(), 5);
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MetaCatUtil.debugMessage("The conection time it has: "
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+db.getConnectionTime(), 5); |
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//set check out time |
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db.setCheckOutTime(System.currentTimeMillis()); |
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//check it out |
| ... | ... | |
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}//else |
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}//if |
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}//for |
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}//sychronize |
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|
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//if couldn't get a connection, we should increase DBConnection pool |
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//if the connection pool size is less than maximum connection number |
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int poolSize = connectionPool.size(); |
| ... | ... | |
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} |
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//Try to run a simple query |
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conn = dbConn.getConnection(); |
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conn = dbConn.getConnections();
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try |
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{
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long startTime=System.currentTimeMillis(); |
| ... | ... | |
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|
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}//validateDBConnection() |
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/** |
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* Method to return a connection to DBConnection pool. |
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* @param conn, the Connection object need to check in |
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*/ |
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public static synchronized void returnDBConnection(DBConnection conn) |
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{
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int index = -1; |
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DBConnection dbConn = null; |
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index = getIndexOfPoolForConnection(conn); |
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if ( index ==-1 ) |
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{
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MetaCatUtil.debugMessage("Couldn't find a DBConnection in the pool"
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+" which have same tag to the returned" |
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+" DBConnetion object"); |
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return; |
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}//if |
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else |
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{
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dbConn = (DBConnection) connectionPool.elementAt(index); |
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//set status to free |
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dbConn.setStatus(FREE); |
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//count check out time |
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dbConn.setConnectionTime |
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(System.currentTimeMillis()-dbConn.getCheckOutTime()); |
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MetaCatUtil.debugMessage("Connection: "+dbConn.getTag()+" checked in.",
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5); |
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}//else |
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}//returnConnection |
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|
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/** |
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* Given a returned DBConnection, try to find the index of DBConnection object |
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* in dbConnection pool by comparing DBConnection' tag and conn.toString. |
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* If couldn't find , -1 will be returned. |
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* @param conn, the connection need to be found |
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*/ |
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private static synchronized int getIndexOfPoolForConnection(DBConnection conn) |
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{
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int index = -1; |
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String info = null; |
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//get tag of this returned DBConnection |
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info = conn.getTag(); |
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//if the tag is null or empty, -1 will be returned |
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if (info==null || info.equals(""))
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{
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return index; |
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} |
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//compare this info to the tag of every DBConnection in the pool |
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for ( int i=0; i< connectionPool.size(); i++) |
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{
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DBConnection dbConn = (DBConnection) connectionPool.elementAt(i); |
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if (info.equals(dbConn.getTag())) |
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{
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index = i; |
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break; |
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}//if |
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}//for |
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return index; |
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}//getIndexOfPoolForConnection |
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|
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/** |
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* Method to shut down all connections |
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*/ |
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public static void release() |
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{
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//shut down the backgroud recycle thread |
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runner.interrupt(); |
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//cose every dbconnection in the pool |
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synchronized(connectionPool) |
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{
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for (int i=0;i<connectionPool.size();i++) |
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{
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try |
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{
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DBConnection dbConn= (DBConnection) connectionPool.elementAt(i); |
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dbConn.close(); |
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}//try |
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catch (SQLException e) |
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{
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MetaCatUtil.debugMessage("Error in release connection: "
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+e.getMessage(), 10); |
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}//catch |
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}//for |
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}//synchronized |
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}//release() |
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|
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/** |
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* periodically to recycle the connection |
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*/ |
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public void run() |
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{
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DBConnection dbConn = null; |
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//keep the thread running |
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while (true) |
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{
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//check every dbconnection in the pool |
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synchronized(connectionPool) |
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{
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for (int i=0; i<connectionPool.size(); i++) |
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{
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dbConn = (DBConnection) connectionPool.elementAt(i); |
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if (dbConn.getStatus() == FREE) |
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{
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try |
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{
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//try to print out the warning message for every connection |
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MetaCatUtil.debugMessage("Warning for connection "+dbConn.getTag()
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+" : "+ dbConn.getWarningMessage(), 5); |
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//check if it is valiate, if not create new one and replace old one |
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if (!validateDBConnection(dbConn)) |
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{
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//close this DBConnection |
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dbConn.close(); |
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//remove it form connection pool |
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connectionPool.remove(i); |
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//insert a new DBConnection to same palace |
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dbConn = new DBConnection(); |
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connectionPool.insertElementAt(dbConn, i); |
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}//if |
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}//try |
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catch (SQLException e) |
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{
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MetaCatUtil.debugMessage("Error in DBConnectionPool.run: "
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+e.getMessage(), 20); |
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}//catch |
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}//if |
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}//for |
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}//synchronize |
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//sleep 1200 seconds (20 minutes) |
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try |
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{
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Thread.sleep(30000); |
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} |
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catch (Exception e) |
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{
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MetaCatUtil.debugMessage("Error in DBConnectionPool.run: "
|
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+e.getMessage(), 20); |
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} |
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}//while |
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}//run |
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|
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| 271 | 467 |
}//DBConnectionPool |
Also available in: Unified diff
Add some new methods into this class.