如何访问jar文件中文件夹中的文件？

Question

我查看了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?以及其他许多问题，但实际上无法得到答案。我要做的是将jar中的res/CDC.txt中的文件内容复制到jar中的某个地方。现在，在我的计算机上它可以工作，但是当我在不同的计算机上尝试它时，我得到FileNotFoundException。所以，我弄清楚它为什么适用于我的。我将CLASSPATH设置为.;D:\myname\Java\JavaFiles，其中所有java文件都位于包中。在“JavaFiles”目录中还有“res / CDC.txt”。因此，当我启动我的应用程序时，它首先检查myapp.jar所在的当前目录是否为“res / CDC.txt”，然后检查“JavaFiles”并找到它。其他电脑没有它。所以，这是我的初始代码：

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);
}

}

我改为

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);
}

}

这次我总是NullPointerException。那么，如何读取jar中的文件夹和文件？

由于

Answer 1

您需要使用getSystemResourceAsStream()来读取jar中文件的内容。

这当然是假设文件实际上在其他用户计算机的类路径上。