爲FtpClient設置連接超時

Question

將ftpClient.connect與現有主機（未啓用ftp服務）一起使用時，超時僅在5分鐘後發生，這太長了。

我試着設置不同的超時（setDefaultTimeout，setDataTimeout），它沒有改變任何東西。

FtpClient繼承自SocketClient它有一個setConnectTiemout方法，但是當我使用它時，我得到一個java.lang.NoSuchMethodError: org/apache/commons/net/ftp/FTPClient.setConnectTimeout運行它時。這似乎是因爲一些J2SW 1.2兼容性，如Commons-net FAQ中所述：

問：如何設置連接超時？ http://wiki.apache.org/commons/Net/FrequentlyAskedQuestions

他們建議實現自己的SocketFactory使用特定的超時從擴展的Socket類創建對象。但是，當試圖使用ftpClient.setSocketFactory時，我也會得到一個java.lang.NoSuchMethodError。

任何幫助我如何減少連接超時？

Answer 1

雖然對於較舊版本的Commons Net庫有可能的解決方案，但我建議找出爲什麼使用Commons Net的錯誤版本。要做到這一點，你可以包括下面的代碼到FTPClient在你的web應用中使用的地方：

FTPClient ftpClient = ...; 
if(ftpClient.getClass().getClassLoader() instanceof java.net.URLClassLoader) { 
    URL[] urls = ((java.net.URLClassLoader) ftpClient.getClass().getClassLoader()).getURLs(); 
    // log these urls somewhere and check - these are urls from where your FTPClient may be loaded from 
} 

在情況下，如果FTPClient不加載由java.net.URLClassLoader那麼它可能變得更加複雜，檢查類路徑，但它不應該成爲一個問題。

希望這有助於...

Answer 2

它必須以您調用setConnectTimeout的方式進行，因爲它確實存在。 setConnectTimeout不是靜態調用，您必須在分配FTPClient對象並在連接之前執行設置後調用它。

FTPClient ftp = new FTPClient(); 
ftp.setConnectTimeout(5000); // 5000 Milliseconds (5 Seconds) 
... 
ftp.connect(server, port); 

Answer 3

FTPClient ftp = new FTPClient(); 

    ftp.setDefaultTimeout(); 
    ftp.setDataTimeout(); 
    ftp.setConnectTimeout(); 
    ftp.setSoTimeout(); 
    ftp.setControlKeepAliveTimeout(); 
    ftp.setControlKeepAliveReplyTimeout(); 

Apache的文檔：

/** 
    * Set the default timeout in milliseconds to use when opening a socket. 
    * This value is only used previous to a call to 
    * {@link #connect connect()} 
    * and should not be confused with {@link #setSoTimeout setSoTimeout()} 
    * which operates on an the currently opened socket. _timeout_ contains 
    * the new timeout value. 
    * <p> 
    * @param timeout The timeout in milliseconds to use for the socket 
    *     connection. 
    */ 
    void setDefaultTimeout(int timeout); 


    /** 
    * Sets the timeout in milliseconds to use when reading from the 
    * data connection. This timeout will be set immediately after 
    * opening the data connection, provided that the value is &ge; 0. 
    * <p> 
    * <b>Note:</b> the timeout will also be applied when calling accept() 
    * whilst establishing an active local data connection. 
    * @param timeout The default timeout in milliseconds that is used when 
    *  opening a data connection socket. The value 0 means an infinite timeout. 
    */ 
    void setDataTimeout(int timeout) 
    /** 
    * Sets the connection timeout in milliseconds, which will be passed to the {@link java.net.Socket} object's 
    * connect() method. 
    * @param connectTimeout The connection timeout to use (in ms) 
    * @since 2.0 
    */ 
    void setConnectTimeout(int connectTimeout); 
    /** 
    * Set the timeout in milliseconds of a currently open connection. 
    * Only call this method after a connection has been opened 
    * by {@link #connect connect()}. 
    * <p> 
    * To set the initial timeout, use {@link #setDefaultTimeout(int)} instead. 
    * 
    * @param timeout The timeout in milliseconds to use for the currently 
    *     open socket connection. 
    * @exception SocketException If the operation fails. 
    * @throws NullPointerException if the socket is not currently open 
    */ 
    void setSoTimeout(int timeout) throws SocketException; 
    /** 
    * Set the time to wait between sending control connection keepalive messages 
    * when processing file upload or download. 
    * 
    * @param controlIdle the wait (in secs) between keepalive messages. Zero (or less) disables. 
    * @since 3.0 
    * @see #setControlKeepAliveReplyTimeout(int) 
    */ 
    void setControlKeepAliveTimeout(long controlIdle); 

    /** 
    * Set how long to wait for control keep-alive message replies. 
    * 
    * @param timeout number of milliseconds to wait (defaults to 1000) 
    * @since 3.0 
    * @see #setControlKeepAliveTimeout(long) 
    */ 
    void setControlKeepAliveReplyTimeout(int timeout)