자바 데이터베이스 연결 풀-자기가 쓴
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Enumeration;
import java.util.Vector;
/* APACHE COMMONS DBCP ，
， ，
， ，
。*/
public class ConnectionPool {
private String jdbcDriver = ""; //
private String dbUrl = ""; // URL
private String dbUsername = ""; //
private String dbPassword = ""; //
private String testTable = ""; // ，
private int initialConnections = 10; //
private int incrementalConnections = 5;//
private int maxConnections = 50; //
private Vector connections = null; // , null
// PooledConnection
/**
*
*
* @param jdbcDriver String JDBC
* @param dbUrl String URL
* @param dbUsername String
* @param dbPassword String
*
*/
public ConnectionPool(String jdbcDriver, String dbUrl, String dbUsername,
String dbPassword) {
this.jdbcDriver = jdbcDriver;
this.dbUrl = dbUrl;
this.dbUsername = dbUsername;
this.dbPassword = dbPassword;
try {
createPool();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
*
*
* @return
*/
public int getInitialConnections() {
return this.initialConnections;
}
/**
*
*
* @param
*/
public void setInitialConnections(int initialConnections) {
this.initialConnections = initialConnections;
}
/**
* 、
*
* @return
*/
public int getIncrementalConnections() {
return this.incrementalConnections;
}
/**
*
* @param
*/
public void setIncrementalConnections(int incrementalConnections) {
this.incrementalConnections = incrementalConnections;
}
/**
*
* @return
*/
public int getMaxConnections() {
return this.maxConnections;
}
/**
*
*
* @param
*/
public void setMaxConnections(int maxConnections) {
this.maxConnections = maxConnections;
}
/**
*
*
* @return
*/
public String getTestTable() {
return this.testTable;
}
/**
*
* @param testTable String
*/
public void setTestTable(String testTable) {
this.testTable = testTable;
}
/**
*
* ，
* initialConnections
*/
public synchronized void createPool() throws Exception {
//
// ， connections
if (connections != null) {
return; // ，
}
// JDBC Driver
Driver driver = (Driver) (Class.forName(this.jdbcDriver).newInstance());
DriverManager.registerDriver(driver); // JDBC
// , 0
connections = new Vector();
// initialConnections ， 。
createConnections(this.initialConnections);
System.out.println(" ！ ");
}
/**
* numConnections ,
* connections
*
* @param numConnections
*/
private void createConnections(int numConnections) throws SQLException {
//
for (int x = 0; x < numConnections; x++) {
// ？ maxConnections
// ， maxConnections 0 ， 。
// ， 。
if (this.maxConnections > 0
&& this.connections.size() >= this.maxConnections) {
break;
}
//add a new PooledConnection object to connections vector
// （ connections ）
try {
connections.addElement(new PooledConnection(newConnection()));
} catch (SQLException e) {
System.out.println(" ！ " + e.getMessage());
throw new SQLException();
}
System.out.println(" ......");
}
}
/**
*
*
* @return
*/
private Connection newConnection() throws SQLException {
//
Connection conn = DriverManager.getConnection(dbUrl, dbUsername,
dbPassword);
// ， ，
//
//connections.size()==0
if (connections.size() == 0) {
DatabaseMetaData metaData = conn.getMetaData();
int driverMaxConnections = metaData.getMaxConnections();
// driverMaxConnections 0 ，
// ，
//driverMaxConnections ，
// ,
//
if (driverMaxConnections > 0
&& this.maxConnections > driverMaxConnections) {
this.maxConnections = driverMaxConnections;
}
}
return conn; //
}
/**
* getFreeConnection() ,
* ，
* （ ）， 。
*
* @return
*/
public synchronized Connection getConnection() throws SQLException {
//
if (connections == null) {
return null; // ， null
}
Connection conn = getFreeConnection(); //
// ，
while (conn == null) {
//
wait(250);
conn = getFreeConnection(); // ， ，
//getFreeConnection() null
//
}
return conn;//
}
/**
* connections ，
* ， incrementalConnections
* ， 。
* ， ， null
* @return
*/
private Connection getFreeConnection() throws SQLException {
//
Connection conn = findFreeConnection();
if (conn == null) {
//
//
createConnections(incrementalConnections);
//
conn = findFreeConnection();
if (conn == null) {
// ， null
return null;
}
}
return conn;
}
/**
* ， ，
* ， null
*
* @return
*/
private Connection findFreeConnection() throws SQLException {
Connection conn = null;
PooledConnection pConn = null;
//
Enumeration enumerate = connections.elements();
// ，
while (enumerate.hasMoreElements()) {
pConn = (PooledConnection) enumerate.nextElement();
if (!pConn.isBusy()) {
// ，
conn = pConn.getConnection();
pConn.setBusy(true);
//
if (!testConnection(conn)) {
// ， ，
// ， ， null
try {
conn = newConnection();
} catch (SQLException e) {
System.out.println(" ！ " + e.getMessage());
return null;
}
pConn.setConnection(conn);
}
break; // ，
}
}
return conn;//
}
/**
* ， ， false
* true
*
* @param conn
* @return true ， false
*/
private boolean testConnection(Connection conn) {
try {
//
if (testTable.equals("")) {
// ， setAutoCommit()
// （ ， ,
// ）。 ：
conn.setAutoCommit(true);
} else {//
//check if this connection is valid
Statement stmt = conn.createStatement();
stmt.execute("select count(*) from " + testTable);
}
} catch (SQLException e) {
// ， ， ， false;
closeConnection(conn);
return false;
}
// ， true
return true;
}
/**
* ， 。
* 。
*
* @param
*/
public void returnConnection(Connection conn) {
// ， （ ），
if (connections == null) {
System.out.println(" ， !");
return;
}
PooledConnection pConn = null;
Enumeration enumerate = connections.elements();
// ，
while (enumerate.hasMoreElements()) {
pConn = (PooledConnection) enumerate.nextElement();
//
if (conn == pConn.getConnection()) {
// ,
pConn.setBusy(false);
break;
}
}
}
/**
*
*
*/
public synchronized void refreshConnections() throws SQLException {
//
if (connections == null) {
System.out.println(" ， !");
return;
}
PooledConnection pConn = null;
Enumeration enumerate = connections.elements();
while (enumerate.hasMoreElements()) {
//
pConn = (PooledConnection) enumerate.nextElement();
// 5 ,5
if (pConn.isBusy()) {
wait(5000); // 5
}
// ， 。
closeConnection(pConn.getConnection());
pConn.setConnection(newConnection());
pConn.setBusy(false);
}
}
/**
* ， 。
*/
public synchronized void closeConnectionPool() throws SQLException {
// ， ，
if (connections == null) {
System.out.println(" ， !");
return;
}
PooledConnection pConn = null;
Enumeration enumerate = connections.elements();
while (enumerate.hasMoreElements()) {
pConn = (PooledConnection) enumerate.nextElement();
// ， 5
if (pConn.isBusy()) {
wait(5000); // 5
}
//5
closeConnection(pConn.getConnection());
//
connections.removeElement(pConn);
}
//
connections = null;
}
/**
*
*
* @param
*/
private void closeConnection(Connection conn) {
try {
conn.close();
} catch (SQLException e) {
System.out.println(" ： " + e.getMessage());
}
}
/**
*
*
* @param
*/
private void wait(int mSeconds) {
try {
Thread.sleep(mSeconds);
} catch (InterruptedException e) {
}
}
/**
*
* ， ，
* 。
*/
class PooledConnection {
Connection connection = null;//
boolean busy = false; // ，
// ， Connection PooledConnection
public PooledConnection(Connection connection) {
this.connection = connection;
}
//
public Connection getConnection() {
return connection;
}
// ，
public void setConnection(Connection connection) {
this.connection = connection;
}
//
public boolean isBusy() {
return busy;
}
//
public void setBusy(boolean busy) {
this.busy = busy;
}
}
}
/*=======================================
POSTGRESQL ，
。
：
① ConnectionPool connPool
= new ConnectionPool("org.postgresql.Driver"
,"jdbc:postgresql://dbURI:5432/DBName"
,"postgre"
,"postgre");
② connPool .createPool();
Connection conn = connPool .getConnection();
*/
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