连接池实现原理

自己写一个线程池
 
public class OraclePool {
      private static volatile OraclePool pool;
      private OracleDataSource ds;
      private Map<Connection,Boolean> map;
      
      private String url= "jdbc:oracle:thin:@127.0.0.1:1521:orcl" ;
      private String username= "lmdc461";
      private String password= "lmdc";
      private int initPoolSize=10;
      private int maxPoolSize=200;
      private int waitTime=100;
      
      public OraclePool(){
            init();
      }
      
      public static OraclePool getInstance(){
             if ( pool== null) {
                   synchronized (OraclePool. class) {
                         pool= new OraclePool();
                  }
            }
             return pool;
      }
      
      private void init(){
             try {
                   ds= new OracleDataSource();
                   ds.setURL( url);
                   ds.setUser( username);
                   ds.setPassword( password);
                   //ds.set
                   ds.setLoginTimeout(2000);
            
                   map= new HashMap<Connection, Boolean>();
                   for ( int i = 0; i < initPoolSize; i++) {
                         map.put(getNewConnection(), true);
                  }
                  
            } catch (Exception e) {
                   e.printStackTrace();
            }
      }
      
      public Connection getNewConnection(){
             try {
                   return ds.getConnection();
            } catch (Exception e) {
                   e.printStackTrace();
            }
             return null;
      }
      
      public synchronized Connection getConnection(){
            Connection conn= null;
             try {
                   for (Entry<Connection,Boolean> entry : map.entrySet()) {
                         if ( entry.getValue()) {
                               conn= entry.getKey();
                               map.put( entry.getKey(), false);
                               break;
                        }
                  }
                   if ( conn== null) {
                         if ( map.size()< maxPoolSize) {
                               conn=getNewConnection();
                               map.put( conn, false);
                        } else{
                              wait( waitTime);
                               conn=getConnection();
                        }
                  }
                  
            } catch (Exception e) {
                   e.printStackTrace();
            }
             return conn;
      }
      
      public void releaseConnection(Connection conn){
             if ( conn== null) {
                   return ;
            }
             try {
                   if ( map.containsKey( conn)) {
                         if ( conn.isClosed()) {
                               map.remove( conn);
                        } else{
                               if (! conn.getAutoCommit()) {
                                     conn.setAutoCommit( true);
                              }
                               map.put( conn, true);
                        }
                  } else{
                         conn.close();
                  }
            } catch (Exception e) {
                   e.printStackTrace();
            }
      }
}
 
 
使用:
 
 
public class TestOraclePool {
      private static volatile int a;
      
      private synchronized static void incr(){
             a++;
      }
      
      public static void main(String[] args) throws InterruptedException{
             int times=10;
            System. out.println( "start``````````");
             long start=System. currentTimeMillis();
             for ( int i = 0; i < times; i++) {
                   new Thread( new Runnable(){
 
                         @Override
                         public void run() {
                              OraclePool pool= new OraclePool();
                              Connection conn= pool.getConnection();
                              Statement stmt= null;
                              ResultSet rs= null;
                               try {
                                     stmt= conn.createStatement();
                                     rs= stmt.executeQuery( "select * from gd_user");
                                     while ( rs.next()) {
                                          System. out.println( "recordid:"+ rs.getString( "recordid")+
                                                       ";username:"+ rs.getString( "username"));                                       
                                    }
                              } catch (Exception e) {
                                     e.printStackTrace();
                              } finally{
                                     incr();
                                     if ( rs!= null) {
                                           try {
                                                 rs.close();
                                          } catch (Exception e2) {
                                                 // TODO: handle exception
                                          }
                                    }
                                     if ( stmt!= null) {
                                           try {
                                                 stmt.close();
                                          } catch (Exception e2) {
                                                 e2.printStackTrace();
                                          }
                                    }
                                     pool.releaseConnection( conn);
                              }
                        }
                        
                  }).start();
                  
                  
            }
            
             while ( true){
                   if ( a== times) {
                        System. out.println( "finished,time:"+
                                    (System. currentTimeMillis()-start));
                         break;
                  }     
                  Thread. sleep(1000);
            }
      }
}
原文地址:https://www.cnblogs.com/wanglao/p/5329702.html