How to change the Properties.store() divider symbol from “=” to “:”?
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15-04-2021 - |
質問
I recently found out about java.util.Properties
, which allows me to write and read from a config without writing my own function for it.
I was excited since it is so easy to use, but later noticed a flaw when I stored the modified config file.
Here is my code, quite simple for now:
FileWriter writer = null;
Properties configFile = new Properties();
configFile.load(ReadFileTest.class.getClassLoader().getResourceAsStream("config.txt"));
String screenwidth = configFile.getProperty("screenwidth");
String screenheight = configFile.getProperty("screenheight");
System.out.println(screenwidth);
System.out.println(screenheight);
configFile.setProperty("screenwidth", "1024");
configFile.setProperty("screenheight", "600");
try {
writer = new FileWriter("config.txt" );
configFile.store(writer, null);
} catch (IOException e) {
e.printStackTrace();
}
writer.flush();
writer.close();
The problem I noticed was that the config file I try to edit is stored like this:
foo: bar
bar: foo
foobar: barfoo
However, the output after properties.store(writer, null)
is this:
foo=bar
bar=foo
foobar=barfoo
The config file I edit is not for my program, it is for an other application that needs the config file to be in the format shown above with :
as divider or else it will reset the configuration to default.
Does anybody know how to easily change this?
I searched through the first 5 Google pages now but found noone with a similar problem.
I also checked the Javadoc and found no function that allows me to change it without writing a class for myself.
I would like to use Properties
for now since it is there and quite easy to use.
I also got the idea of just replacing all =
with :
after I saved the file but maybe someone got a better suggestion?
解決
Don't use a tool that isn't designed for the task - don't use Properties
here. Instead, I'd just write your own - should be easy enough.
You can still use a Properties
instance as your "store", but don't use it for serializing the properties to text. Instead, just use a FileWriter
, iterate through the properties, and write the lines yourself - as key + ": " + value
.
他のヒント
New idea here
Your comment about converting the = to : got me thinking: Properties.store() writes to a Stream. You could use an in-memory ByteArrayOutputStream, convert as appropriate in memory before you write to a file, then write the file. Likewise for Properties.load(). Or you could insert FilterXXXs instead. (I'd probably do it in memory).
I was looking into how hard it would be to subclass. It's nearly impossible. :-(
If you look at the source code for Properties, (I'm looking at Java 6) store() calls store0(). Now, unfortunately, store0 is private, not protected, and the "=" is given as a magic constant, not something read from a property. And it calls another private method called saveConvert() that also has a lot of magic constants.
Overall, I rate this code as D- quality. It breaks almost all the rules of good code and good style.
But, it's open source, so, theoretically, you could copy and paste (and improve!) a bunch of code into your own BetterProperties class.