如何訪問jar文件內的文件夾內的文件？

Question

我看過How to access resources in JAR file?和How do I copy a text file from a jar into a file outside of the jar?以及許多其他questiions，但無法真正得到答案。我想要做的是將文件的res/CDC.txt中的內容複製到jar中的某處。現在，在我的電腦上它可以工作，但是當我在不同的計算機上嘗試時，我得到FileNotFoundException。所以，我找出了它爲什麼對我有用。我有一個CLASSPATH設置爲.;D:\myname\Java\JavaFiles所有我的java文件都位於包中。在「JavaFiles」目錄中還有「res/CDC.txt」。因此，當我啓動我的應用程序時，它首先檢查myapp.jar位於「res/CDC.txt」中的當前目錄，然後檢查「JavaFiles」並找到它。其他電腦沒有它。所以，這是我最初的代碼：

public final class CT 
{ 

//Other fields 
private static CT ct; 
private NTSystem nts; 
private File f1; 
private File f6; 
private PrintWriter pw1; 
private BufferedReader br1; 
//Other fields 

public static void main(String[] args) 
{ 
    try 
    { 
     showMessage("Executing program..."); 
     ct = new CT(); 
     ct.init(); 
     ct.create(); 
     ct.insertData(); 
     //Other code 
     showMessage("Program executed!"); 
    } 
    catch(Exception e) 
    { 
     showMessage("An exception occured! Program closed."); 
     e.printStackTrace(); 
     System.exit(0); 
    } 
} 

private void init() 
    throws IOException 
{ 
    //Other initialization 
    nts = new NTSystem(); 
    f1 = new File("C:\\Users\\" + nts.getName() + "\\blahblah"); 
    f6 = new File("res\\CDC.txt"); 
    br1 = new BufferedReader(new FileReader(f6)); 
    //Other initialization 
    showMessage("Initialized"); 
} 

private void create() 
    throws IOException 
{ 
    //Makes sure file/dir exists, etc 

    pw1 = new PrintWriter(new BufferedWriter(new FileWriter(f1)), true); 
    //Other Stuff 

    showMessage("Created"); 
} 

private void insertData() 
    throws IOException 
{ 
    String line = br1.readLine(); 
    while(line != null) 
    { 
     pw1.println(line); 
     line = br1.readLine(); 
    } 

    //Other stuff 
    showMessage("Data inserted"); 
} 

private static void showMessage(String msg) 
{ 
    System.out.println(msg); 
} 

} 

我改成

public final class CT 
{ 

//Other fields 
private static CT ct; 
private NTSystem nts; 
private byte[] buffer; 
private File f1; 
private URL url1; 
private FileOutputStream fos1; 
private InputStream is1; 
//Other fields 

public static void main(String[] args) 
{ 
    try 
    { 
     showMessage("Executing program..."); 
     ct = new CT(); 
     ct.init(); 
     ct.create(); 
     ct.insertData(); 
     //Other code 
     showMessage("Program executed!"); 
    } 
    catch(Exception e) 
    { 
     showMessage("An exception occured! Program closed."); 
     e.printStackTrace(); 
     System.exit(0); 
    } 
} 

private void init() 
    throws IOException 
{ 
    //Other initialization 
    nts = new NTSystem(); 
    buffer = new byte[4096]; 
    f1 = new File("C:\\Users\\" + nts.getName() + "\\blahblah"); 
    url1 = getClass().getClassLoader.getResource("res\\CDC.txt"); //Also tried url1 = ct.getClass().getClassLoader.getResource("res\\CDC.txt"); or url1 = this.getClass().getClassLoader.getResource("res\\CDC.txt"); or url1 = CT.getClass().getClassLoader.getResource("res\\CDC.txt"); 
    is1 = url1.openStream(); 
    //Other initialization 
    showMessage("Initialized"); 
} 

private void create() 
    throws IOException 
{ 
    //Makes sure file/dir exists, etc 

    pw1 = new PrintWriter(new BufferedWriter(new FileWriter(f1)), true); 
    //Other Stuff 

    showMessage("Created"); 
} 

private void insertData() 
    throws IOException 
{ 
    int read = is1.read(buffer); 
    while(line != null) 
    { 
     fos1.write(buffer, 0, read); 
     read = is1.read(buffer); 
    } 

    //Other stuff 
    showMessage("Data inserted"); 
} 

private static void showMessage(String msg) 
{ 
    System.out.println(msg); 
} 

} 

這一次，我總是得到NullPointerException。那麼，如何閱讀jar中的文件夾和文件？

感謝

Answer 1

你將要使用getSystemResourceAsStream()來讀取文件的內容，在一個罐子裏。

這當然假設該文件實際上是在其他用戶計算機的類路徑上。