synchronized 和lock 在一起用的时候需要考虑到哪些注意事项？ - 黑马程序员技术交流社区

public class ConnectionManager {
private Logger logger = LoggerFactory.getLogger(ConnectionManager.class);
public static final ConnectionManager instance = new ConnectionManager();
private ReentrantLock locker = new ReentrantLock();
private ConnectionPool pool;
private ConnectionManager(){
pool = new ConnectionPool();
}
public static ConnectionManager getInstance(){
return instance;
}
public Connection getConnection(){
locker.lock();
try{
return pool.getConnection();
}finally{
locker.unlock();
}
}
public void revertConnection(Connection conn){
locker.lock();
try{
pool.revertConnection(conn);
}finally{
locker.unlock();
}
}

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package com.ourgame.clown.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.ourgame.clown.ClownData;
import com.ourgame.clown.config.ServerConfig;
public class ConnectionPool {
private Logger logger = LoggerFactory.getLogger(ConnectionPool.class);
private ConcurrentLinkedQueue<DBConn> queue;
private AtomicInteger amount = new AtomicInteger(0);
public ConnectionPool(){
queue = new ConcurrentLinkedQueue<DBConn>();
}
public Connection refreshConnection(Connection conn){
try{
conn.close();
}catch(Exception e){}
return createConnection();
}
public void revertConnection(Connection conn){
if(conn == null){
amount.decrementAndGet();
return;
}
synchronized(queue){
queue.add(new DBConn(conn));
queue.notify();
}
}
public synchronized Connection getConnection(){
//连接只要闲置超过一分半分钟，则抛弃不要了
long time = System.currentTimeMillis();
synchronized(queue){
while(queue.size()>0){
DBConn sl = queue.poll();
if(time - sl.activeTime>90000){
try{
sl.conn.close();
logger.debug("DBManager Close a overtime connection. connection amount="+amount.decrementAndGet()+" queue size="+queue.size());
}catch(Exception e){}
continue;
}else{
logger.debug("DBManager getConnection. connection amount="+amount.get()+" queue size="+queue.size());
return sl.conn;
}
}
}
try{
return createConnection();
}catch(Exception e){
e.printStackTrace(System.err);
return null;
}
}
private synchronized Connection createConnection(){
Connection conn = null;
try{
ServerConfig config = ClownData.getInstance().getServerConfig();
Class.forName(config.getDbDriver());
String url = config.getDbDriverURL();
if(config.getDbMirror() != null && config.getDbMirror().length()>0){
url += ";failover partner="+config.getDbMirror();
}
conn = DriverManager.getConnection(url,
config.getDbUser(),
config.getDbPass());
}catch(Exception e){
logger.debug("Fatal Error create db connection failed.");
}
amount.incrementAndGet();
return conn;
}
class DBConn{
public long activeTime;
public Connection conn;
public DBConn(Connection conn){
this.conn = conn;
this.activeTime = System.currentTimeMillis();
}
}
}

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