Properties.load() ignores '\'

[Yaroslav Chinskiy]

Hi,

I have a properties file that contains a path in the form c:\test\tmp

If I use standard Properties.load method, it will strip all '\'

I can not modify the config file and must process as is.

Any advice?

[Mark Vedder]

I'm no I/O guru, so there may be a better way of doing this, but you could write a custom FilterInputStream to convert the black slashes into forward slashes since Java will take C:/test/myfile.txt as a vaild file path for windows. (It would also take C:\\test\\myfile.txt). However to add the extra escape character would take a little bit more work since you need to add a character to the input stream, likely via a BufferedInputStream or BufferedReader.

Here's a quick trial I did that seems to work fine (with very limited testing), converting c:\test\tmp
to c:/test/tmp. Of course this will convert ALL '\' characters to '/'. Not a problem if you only have file paths in your properties file, If not, you'll to make it a bit more fancy, perhaps changing all '\' to '\\', but like I said, that gets to be a bit more complicated, but certainly could be done via some type of BufferedReader or Stream.

 
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
 
public class BackSlashFilter extends FilterInputStream
{
    public BackSlashFilter (InputStream in)
    {
        super(in);
    }
 
    public int read() throws IOException
    {
        int b = in.read();
        // printing, ASCII characters
        if ( b == 92 )
        {
            b = 47;
        }
 
        return b;
    }
 
    public int read(byte[] data, int offset, int length) throws IOException
    {
 
        int result = in.read(data, offset, length);
        for ( int i = offset; i < offset + result; i++ )
        {
            // Do nothing with the printing characters.
            if ( data[i] == 92 )
            {
                data[i] = 47;
            }
        }
        return result;
    }
}

A demo program:

 
import java.util.Properties;
import java.io.IOException;
import java.io.InputStream;
import java.io.FileInputStream;
 
public class Demo
{
    public static void main(String[] args)
    {
        Demo demo = new Demo();
        demo.go();
        System.exit(0);
    }
 
    private void go()
    {
        try
        {
            InputStream is = new BackSlashFilter(new FileInputStream("D:/Dev/test.properties"));
 
            Properties prop = new Properties();
            prop.load(is);
            String value = prop.getProperty("key");
            System.out.println(value);
        }
        catch (IOException ioe)
        {
            //:TODO: Add better Exception Handling
            ioe.printStackTrace();
        }
    }
}
 

A sheriff may want to move this to the I/O forum to get some input (no pun intended) from the gurus that hang out in that forum.
[ March 15, 2005: Message edited by: Mark Vedder ]

[ramprasad madathil]

Do not use File operations to load your properties.
.Here's an excellent article that tells why and also details the correct approach (Use ClassLoader and Class apis)

ram

[Mark Vedder]

That is a good point, and I agree it is generally better to use a ClassLoader then a a java.io.File to load the properties. I typically do so myself. In the above post, my focus was on the FilterInputStream to solve Yaroslav's problem, and therefore I wrote a quick demo program to illustrate its use. The same technique could be used on the wrap the InputStream received via using a ClassLoader to "find" the properties file.