Modifying a property file while maintaining the order as well as comments

It doesn’t get much better than Apache’s Commons Configuration API. This provides a unified approach to configuration from Property files, XML, JNDI, JDBC datasources, etc.

It’s handling of property files is very good. It allows you to generate a PropertiesConfigurationLayout object from your property which preserves as much information about your property file as possible (whitespaces, comments etc). When you save changes to the property file, these will be preserved as best as possible.

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStreamReader;
 
import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.configuration.PropertiesConfiguration;
import org.apache.commons.configuration.PropertiesConfigurationLayout;
 
public class PropertiesReader {
    public static void main(String args[]) throws ConfigurationException, FileNotFoundException {
        File file = new File(args[0] + ".properties");
 
        PropertiesConfiguration config = new PropertiesConfiguration();
        PropertiesConfigurationLayout layout = new PropertiesConfigurationLayout(config);
        layout.load(new InputStreamReader(new FileInputStream(file)));
 
        config.setProperty("test", "testValue");
        layout.save(new FileWriter("path\\to\\properties\\file.properties", false));
    }
}

Uday Ogra

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