Java连接池实现 [英] Java Connection Pool implementation

问题描述

  public class ConnectionPool {
 private static List< DBConnection> pool = null; 
 private static int available = 0; 
 private ConnectionPool（）{} 
 
 public static DBConnection getConnection（）{
 if（pool == null）{
 pool = new ArrayList< DBConnection> ; 
 for（int i = 0; i <3; i ++）{
 try {
 pool.add（new DBConnection（））; 
可用++; 
} catch（SQLException e）{
 e.printStackTrace（）; 
} 
} 
} 
 if（pool.size（）> 0）{
 available--; 
 return pool.remove（available）; 
} else {
 return null; 
} 
} 
 
 public static void returnConnection（DBConnection c）{
 pool.add（c）; 
可用++; 
} 
} 
  

我只使用一个数组，请求连接池连接使用它，然后将其返回到连接池。

 连接连接= ConnectionPool.getConnection ; 
 connection.execute（insert into users values（'+ user.getUsername（）+'，'+ user.getPassword（）+'，'+ user.getGroup（） '+ banned +'，'+ broker + admin + sharehodler + company +'））; 
 ConnectionPool.returnConnection（connection）; 
 connection = null; 
  

请与我联系。谢谢

解决方案

有一些要点会使此实现非常有问题。

• 线程安全。如果几个线程与池一起工作怎么办？


• 3个连接的静态最大池大小，也可以立即创建所有这些连接，无论是否需要。一个常见的策略是创建一堆连接，并在需要时创建一些连接，直到达到允许/配置的最大值。


• 您只有静态方法。应该可以有几个池，这意味着您需要 ConnectionPool 的实例。


• 没有办法传递host + dbname + user +


• 您不处理断开的连接 - 如果现有的连接断开，您可能必须重新创建连接。


• 使用配置值而不是静态值，请参阅第2点


• 最后：确实，有趣的是自己写这个东西 - 但如果你需要一个项目池，选择一个现有的，如 c3p0 或 tomcat连接池。

我确定还有更多要指出的，但除非这些都是固定的，否则不能继续使用。

can you look at my connection pool if it is a possible way to implement it?

public class ConnectionPool {
    private static List<DBConnection> pool = null;
    private static int available = 0;
    private ConnectionPool() {}

    public static DBConnection getConnection() {
        if (pool == null) {
             pool = new ArrayList<DBConnection>();
             for (int i = 0; i < 3; i++) {
                 try {
                    pool.add(new DBConnection());
                    available++;
                } catch (SQLException e) {
                    e.printStackTrace();
                }
             }
        }
        if (pool.size() > 0) {
            available--;
            return pool.remove(available);
        } else {
            return null;
        }
    }

    public static void returnConnection(DBConnection c) {
        pool.add(c);
        available++;
    }
}

I'm using only one array and the client should ask the connection pool for a connection use it and then return it to the connection pool.

  Connection connection = ConnectionPool.getConnection();
  connection.execute("insert into users values('"+user.getUsername()+"', '"+user.getPassword()+"', '"+user.getGroup()+"', '"+banned+"', '"+broker+admin+sharehodler+company+"')");      
  ConnectionPool.returnConnection(connection);
  connection = null;

Please I need feedback on this implementation. Thank you

解决方案

There are some points that make this implementation very problematic.

• Thread safety. What if several threads work with the pool? You are not locking the list on read/write access.
• Static maximum pool size of 3 connections, also you immediately create all of them, whether they are needed or not. A common strategy is to create a bunch of connections and create some more when needed, until the allowed/configured maximum is reached.
• You only have static methods. It should be possible to have several pools, meaning you need instances of ConnectionPool.
• No way to pass host+dbname+user+password to the connections that are created.
• You don't deal with 'broken' connections - you may have to re-create a connection if an existing one screwed up. This is far more relevant than I thought before I started using pools.
• Use config values instead of static values, see point #2
• Lastly: sure, it's interesting to write this stuff yourself - but if you need a pool for a project, pick an existing one, such as c3p0 or the tomcat connection pool.

I'm sure there's more to point out, but unless these are fixed, there's no use in continuing.

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