看来并不难。不过不建议这种写法,因为应该尽量避免使用 Java Interface, 关于 Java Interface 的缺点我另外再写文章讨论。大家关注的是 Connection Pool 的实现方法。下面给出一种实现方法。 import java.sql.*;
import java.lang.reflect.*;
import java.util.*;
import java.io.*;public class SimpleConnetionPool {
private static LinkedList m_notUsedConnection = new LinkedList();
private static HashSet m_usedUsedConnection = new HashSet();
private static String m_url = "";
private static String m_user = "";
private static String m_password = "";
static final boolean DEBUG = true;
static private long m_lastClearClosedConnection = System.currentTimeMillis();
public static long CHECK_CLOSED_CONNECTION_TIME = 4 * 60 * 60 * 1000; //4 hours static {
initDriver();
} private SimpleConnetionPool() {
} private static void initDriver() {
Driver driver = null;
//load mysql driver
try {
driver = (Driver) Class.forName("com.mysql.jdbc.Driver").newInstance();
installDriver(driver);
} catch (Exception e) {
} //load postgresql driver
try {
driver = (Driver) Class.forName("org.postgresql.Driver").newInstance();
installDriver(driver);
} catch (Exception e) {
}
} public static void installDriver(Driver driver) {
try {
DriverManager.registerDriver(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
public static synchronized Connection getConnection() {
clearClosedConnection();
while (m_notUsedConnection.size() > 0) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.removeFirst();
if (wrapper.connection.isClosed()) {
continue;
}
m_usedUsedConnection.add(wrapper);
if (DEBUG) {
wrapper.debugInfo = new Throwable("Connection initial statement");
}
return wrapper.connection;
} catch (Exception e) {
}
}
int newCount = getIncreasingConnectionCount();
LinkedList list = new LinkedList();
ConnectionWrapper wrapper = null;
for (int i = 0; i < newCount; i++) {
wrapper = getNewConnection();
if (wrapper != null) {
list.add(wrapper);
}
}
if (list.size() == 0) {
return null;
}
wrapper = (ConnectionWrapper) list.removeFirst();
m_usedUsedConnection.add(wrapper); m_notUsedConnection.addAll(list);
list.clear(); return wrapper.connection;
} private static ConnectionWrapper getNewConnection() {
try {
Connection con = DriverManager.getConnection(m_url, m_user, m_password);
ConnectionWrapper wrapper = new ConnectionWrapper(con);
return wrapper;
} catch (Exception e) {
e.printStackTrace();
}
return null;
} static synchronized void pushConnectionBackToPool(ConnectionWrapper con) {
boolean exist = m_usedUsedConnection.remove(con);
if (exist) {
m_notUsedConnection.addLast(con);
}
} public static int close() {
int count = 0; Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
try {
( (ConnectionWrapper) iterator.next()).close();
count++;
} catch (Exception e) {
}
}
m_notUsedConnection.clear(); iterator = m_usedUsedConnection.iterator();
while (iterator.hasNext()) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
wrapper.close();
if (DEBUG) {
wrapper.debugInfo.printStackTrace();
}
count++;
} catch (Exception e) {
}
}
m_usedUsedConnection.clear(); return count;
} private static void clearClosedConnection() {
long time = System.currentTimeMillis();
//sometimes user change system time,just return
if (time < m_lastClearClosedConnection) {
time = m_lastClearClosedConnection;
return;
}
//no need check very often
if (time - m_lastClearClosedConnection < CHECK_CLOSED_CONNECTION_TIME) {
return;
}
m_lastClearClosedConnection = time; //begin check
Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
try {
if (wrapper.connection.isClosed()) {
iterator.remove();
}
} catch (Exception e) {
iterator.remove();
if (DEBUG) {
System.out.println("connection is closed, this connection initial StackTrace");
wrapper.debugInfo.printStackTrace();
}
}
} //make connection pool size smaller if too big
int decrease = getDecreasingConnectionCount();
if (m_notUsedConnection.size() < decrease) {
return;
} while (decrease-- > 0) {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.removeFirst();
try {
wrapper.connection.close();
} catch (Exception e) {
}
}
} /**
* get increasing connection count, not just add 1 connection
* @return count
*/
public static int getIncreasingConnectionCount() {
int count = 1;
int current = getConnectionCount();
count = current / 4;
if (count < 1) {
count = 1;
}
return count;
} /**
* get decreasing connection count, not just remove 1 connection
* @return count
*/
public static int getDecreasingConnectionCount() {
int count = 0;
int current = getConnectionCount();
if (current < 10) {
return 0;
}
return current / 3;
}
import java.lang.reflect.*;
import java.util.*;
import java.io.*;public class SimpleConnetionPool {
private static LinkedList m_notUsedConnection = new LinkedList();
private static HashSet m_usedUsedConnection = new HashSet();
private static String m_url = "";
private static String m_user = "";
private static String m_password = "";
static final boolean DEBUG = true;
static private long m_lastClearClosedConnection = System.currentTimeMillis();
public static long CHECK_CLOSED_CONNECTION_TIME = 4 * 60 * 60 * 1000; //4 hours static {
initDriver();
} private SimpleConnetionPool() {
} private static void initDriver() {
Driver driver = null;
//load mysql driver
try {
driver = (Driver) Class.forName("com.mysql.jdbc.Driver").newInstance();
installDriver(driver);
} catch (Exception e) {
} //load postgresql driver
try {
driver = (Driver) Class.forName("org.postgresql.Driver").newInstance();
installDriver(driver);
} catch (Exception e) {
}
} public static void installDriver(Driver driver) {
try {
DriverManager.registerDriver(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
public static synchronized Connection getConnection() {
clearClosedConnection();
while (m_notUsedConnection.size() > 0) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.removeFirst();
if (wrapper.connection.isClosed()) {
continue;
}
m_usedUsedConnection.add(wrapper);
if (DEBUG) {
wrapper.debugInfo = new Throwable("Connection initial statement");
}
return wrapper.connection;
} catch (Exception e) {
}
}
int newCount = getIncreasingConnectionCount();
LinkedList list = new LinkedList();
ConnectionWrapper wrapper = null;
for (int i = 0; i < newCount; i++) {
wrapper = getNewConnection();
if (wrapper != null) {
list.add(wrapper);
}
}
if (list.size() == 0) {
return null;
}
wrapper = (ConnectionWrapper) list.removeFirst();
m_usedUsedConnection.add(wrapper); m_notUsedConnection.addAll(list);
list.clear(); return wrapper.connection;
} private static ConnectionWrapper getNewConnection() {
try {
Connection con = DriverManager.getConnection(m_url, m_user, m_password);
ConnectionWrapper wrapper = new ConnectionWrapper(con);
return wrapper;
} catch (Exception e) {
e.printStackTrace();
}
return null;
} static synchronized void pushConnectionBackToPool(ConnectionWrapper con) {
boolean exist = m_usedUsedConnection.remove(con);
if (exist) {
m_notUsedConnection.addLast(con);
}
} public static int close() {
int count = 0; Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
try {
( (ConnectionWrapper) iterator.next()).close();
count++;
} catch (Exception e) {
}
}
m_notUsedConnection.clear(); iterator = m_usedUsedConnection.iterator();
while (iterator.hasNext()) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
wrapper.close();
if (DEBUG) {
wrapper.debugInfo.printStackTrace();
}
count++;
} catch (Exception e) {
}
}
m_usedUsedConnection.clear(); return count;
} private static void clearClosedConnection() {
long time = System.currentTimeMillis();
//sometimes user change system time,just return
if (time < m_lastClearClosedConnection) {
time = m_lastClearClosedConnection;
return;
}
//no need check very often
if (time - m_lastClearClosedConnection < CHECK_CLOSED_CONNECTION_TIME) {
return;
}
m_lastClearClosedConnection = time; //begin check
Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
try {
if (wrapper.connection.isClosed()) {
iterator.remove();
}
} catch (Exception e) {
iterator.remove();
if (DEBUG) {
System.out.println("connection is closed, this connection initial StackTrace");
wrapper.debugInfo.printStackTrace();
}
}
} //make connection pool size smaller if too big
int decrease = getDecreasingConnectionCount();
if (m_notUsedConnection.size() < decrease) {
return;
} while (decrease-- > 0) {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.removeFirst();
try {
wrapper.connection.close();
} catch (Exception e) {
}
}
} /**
* get increasing connection count, not just add 1 connection
* @return count
*/
public static int getIncreasingConnectionCount() {
int count = 1;
int current = getConnectionCount();
count = current / 4;
if (count < 1) {
count = 1;
}
return count;
} /**
* get decreasing connection count, not just remove 1 connection
* @return count
*/
public static int getDecreasingConnectionCount() {
int count = 0;
int current = getConnectionCount();
if (current < 10) {
return 0;
}
return current / 3;
}
printDebugMsg(System.out);
} public synchronized static void printDebugMsg(PrintStream out) {
if (DEBUG == false) {
return;
}
StringBuffer msg = new StringBuffer();
msg.append("debug message in " + SimpleConnetionPool.class.getName());
msg.append("\r\n");
msg.append("total count is connection pool: " + getConnectionCount());
msg.append("\r\n");
msg.append("not used connection count: " + getNotUsedConnectionCount());
msg.append("\r\n");
msg.append("used connection, count: " + getUsedConnectionCount());
out.println(msg);
Iterator iterator = m_usedUsedConnection.iterator();
while (iterator.hasNext()) {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
wrapper.debugInfo.printStackTrace(out);
}
out.println();
} public static synchronized int getNotUsedConnectionCount() {
return m_notUsedConnection.size();
} public static synchronized int getUsedConnectionCount() {
return m_usedUsedConnection.size();
} public static synchronized int getConnectionCount() {
return m_notUsedConnection.size() + m_usedUsedConnection.size();
} public static String getUrl() {
return m_url;
} public static void setUrl(String url) {
if (url == null) {
return;
}
m_url = url.trim();
} public static String getUser() {
return m_user;
} public static void setUser(String user) {
if (user == null) {
return;
}
m_user = user.trim();
} public static String getPassword() {
return m_password;
} public static void setPassword(String password) {
if (password == null) {
return;
}
m_password = password.trim();
}}class ConnectionWrapper implements InvocationHandler {
private final static String CLOSE_METHOD_NAME = "close";
public Connection connection = null;
private Connection m_originConnection = null;
public long lastAccessTime = System.currentTimeMillis();
Throwable debugInfo = new Throwable("Connection initial statement"); ConnectionWrapper(Connection con) {
this.connection = (Connection) Proxy.newProxyInstance(
con.getClass().getClassLoader(),
con.getClass().getInterfaces(), this);
m_originConnection = con;
} void close() throws SQLException {
m_originConnection.close();
} public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
Object obj = null;
if (CLOSE_METHOD_NAME.equals(m.getName())) {
SimpleConnetionPool.pushConnectionBackToPool(this);
}
else {
obj = m.invoke(m_originConnection, args);
}
lastAccessTime = System.currentTimeMillis();
return obj;
}
}使用方法public class TestConnectionPool{
public static void main(String[] args) {
SimpleConnetionPool.setUrl(DBTools.getDatabaseUrl());
SimpleConnetionPool.setUser(DBTools.getDatabaseUserName());
SimpleConnetionPool.setPassword(DBTools.getDatabasePassword()); Connection con = SimpleConnetionPool.getConnection();
Connection con1 = SimpleConnetionPool.getConnection();
Connection con2 = SimpleConnetionPool.getConnection(); //do something with con ... try {
con.close();
} catch (Exception e) {} try {
con1.close();
} catch (Exception e) {} try {
con2.close();
} catch (Exception e) {} con = SimpleConnetionPool.getConnection();
con1 = SimpleConnetionPool.getConnection();
try {
con1.close();
} catch (Exception e) {} con2 = SimpleConnetionPool.getConnection();
SimpleConnetionPool.printDebugMsg(); }
}运行测试程序后打印连接池中 Connection 状态, 以及正在使用的没有关闭 Connection 信息。
我改成把已经使用的和没有使用的connection 分开,getConnection 时候使用m_notUsedConnection.removeFirst(),比较快。
public static int getIncreasingConnectionCount() 是我随意写的,可能不是最好的,不过当 ConnectionPool 中 connection 数量稳定后,这个函数不会被调用,所以问题也不大。如果你的B/S 应用connection 数量可能急剧增加,比如晚上 connection 数量小于 10, 早上再很短的时间内增加到 1000,可能需要修改 getIncreasingConnectionCount。我现在用的是在现有数量上增加 1/4 ,你可能需要改成增加 1/2 或者 1。对于 C/S 应用,没有必要大幅度增加connection 数量,那样会增加 database server 负担。
jndi 我没有用到。因为我觉得可以不用就不用,简单化处理。
如果你要用,自己另外加代码,不过可能程序变得很复杂。
java.lang.ClassCastException at zxctc.sql.connection.ConnectionWrapper.<init>(SimpleConnetionPool.java:441) at zxctc.sql.connection.SimpleConnetionPool.getNewConnection(SimpleConnetionPool.java:149) at zxctc.sql.connection.SimpleConnetionPool.getConnection(SimpleConnetionPool.java:121) at zxctc.sql.connection.TestConnectionPool.main(TestConnectionPool.java:13)
我会测试这个问题。
建议你将出错的前一行加 System.out.println( object.getClass().getName() )输出信息,
如果不能输出到 System.out, 也可以输出到文件
ConnectionWrapper(Connection con) {
Class[] interfaces = {java.sql.Connection.class};
try {
this.connection = (Connection) Proxy.newProxyInstance(
con.getClass().getClassLoader(),
interfaces, this);
m_originConnection = con;
} catch (Exception e) {
e.printStackTrace();
}
}
import cn.com.ge.gemsit.dragonqs.common.*;
import java.sql.*;
import java.util.*;public class TestSqlServer {
public TestSqlServer() {
} public static void main(String[] args) {
Driver driver = new com.microsoft.jdbc.sqlserver.SQLServerDriver();
SimpleConnetionPool.installDriver(driver);
String url = "jdbc:microsoft:sqlserver://192.168.100.1:1433;DatabaseName=pubs;SendStringParametersAsUnicode=true";
SimpleConnetionPool.setUrl(url);
SimpleConnetionPool.setUser("sa");
SimpleConnetionPool.setPassword(""); Connection con = null;
try {
con = SimpleConnetionPool.getConnection();
DatabaseMetaData dmd = con.getMetaData();
System.out.println("connect to database " + dmd.getDatabaseProductName()
+ " " + dmd.getDatabaseProductVersion() + " ok"); String sql = "SELECT COUNT(*) AS count FROM employee";
PreparedStatement ps = con.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
rs.next();
int count = rs.getInt("count");
System.out.println("there are " + count + " employee records in pubs database"); } catch (Exception e) {
System.out.println("fail to connect to sql server");
e.printStackTrace();
}
}}