删除属性文件Java中的注释

Question

when i updated the properties file the comments are also updated along the data .is there any possible way to remove the comments or updating the data without comment.

Here i update the file 4 times each time the date-time stamp append as a comment

#Thu May 19 17:53:42 GMT+05:30 2011
Key_1=DSA_1024
#Thu May 19 17:53:43 GMT+05:30 2011
Key_2=DSA_1024
#Thu May 19 17:53:43 GMT+05:30 2011
Key_3=DSA_1024
#Thu May 19 17:53:44 GMT+05:30 2011
Key_4=DSA_1024

code

  Properties prop=new Properties();
            String currentDirectary=System.getProperty("user.dir");
            String path=currentDirectary+"/Resource/Key.Properties";
            FileOutputStream out=new FileOutputStream(path,true);
            prop.setProperty("keyName","DSA_1024");
            prop.store(out, null);

Answer 1

I once had to do this because a consumer of the properties file couldn't handle the properties. The comment produced by the store method is well defined, so it's easy enough to skip over it:

Writer stringOut = new StringWriter();
properties.store(stringOut, null);
String string = stringOut.toString();
String sep = System.getProperty("line.separator");
out.write(string.substring(string.indexOf(sep) + sep.length()));

Answer 2

Here's an improvement of the hack above which uses the right encoding as well.

FileOutputStream out = new FileOutputStream(filename);
ByteArrayOutputStream arrayOut = new ByteArrayOutputStream();
props.store(arrayOut, null);
String string = new String(arrayOut.toByteArray(), "8859_1");
String sep = System.getProperty("line.separator");
String content = string.substring(string.indexOf(sep) + sep.length());
out.write(content.getBytes("8859_1"));

Answer 3

From the JavaDocs for properties.store()

If the comments argument is not null, then an ASCII # character, the comments string, and a line separator are first written to the output stream. Thus, the comments can serve as an identifying comment.

Next, a comment line is always written, consisting of an ASCII # character, the current date and time (as if produced by the toString method of Date for the current time), and a line separator as generated by the Writer.

The only option I can think of would be to write your ownOutputStream implementation to drop the comments. ( Or just learn to live with them :) )

Answer 4

In groovy I wrote this to entirely remove comments from the Properties.

String writeProperties(Properties properties) {
    def writer = new StringWriter()
    properties.each { k, v ->
         writer.write("${k}=${v}${System.lineSeparator()}")
    }
    writer.toString()
}

This should be easy to convert to regular java.