A better class to update property files?

问题

Though java.util.properties allows reading and writing properties file, the writing does not preserve the formatting. Not surprising, because it is not tied to the property file.

Is there a PropertyFile class out there -- or some such -- that preserves comments and blank lines and updates property values in place?

回答1:

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.

Sample code:

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));
    }
}

回答2:

The sample code for using the Apache Commons Configuration library contributed by Patrick Boos is unnecessarily complicated. You don't need to use PropertiesConfigurationLayout explicitly unless you require some advanced control over the output. PropertiesConfiguration by itself is sufficient to preserve comments and formatting:

PropertiesConfiguration config = new PropertiesConfiguration("myprops.properties");
config.setProperty("Foo", "Bar");
config.save();

(Note: This code works for the existing 1.10 stable version. I have not checked if it works on the 2.0 alpha builds currently available.)

回答3:

You can have a look to the Apache Commons Configuration, that contains PropertiesConfiguration class. However, as I have never used it, I don't know if it preserves the comments and formatting...

However, it worthes a try...

回答4:

The configuration2 class have different syntax. Here is an example using them:

import org.apache.commons.configuration2.PropertiesConfiguration;
import org.apache.commons.configuration2.PropertiesConfigurationLayout;

public void test() {
    PropertiesConfiguration config = new PropertiesConfiguration();
    PropertiesConfigurationLayout layout = new PropertiesConfigurationLayout();
    config.setLayout(layout);
    layout.load(config, new FileReader("config.properties"));

    config.setProperty("KEY", "VALUE");
    StringWriter stringWriter = new StringWriter();
    layout.save(config, stringWriter);
    LOG.debug("Properties:\n{}", stringWriter.toString());
}

回答5:

    File file = new File("src/test/resources/1automation.properties");
    PropertiesConfiguration config = new PropertiesConfiguration();
    PropertiesConfigurationLayout layout = new PropertiesConfigurationLayout(config);
    layout.load(new InputStreamReader(new FileInputStream(file)));
    FileWriter fw = new FileWriter("src/test/resources/1automation.properties",false);
    config.setProperty("myssi.admin.name", "testValue");
    layout.save(fw);

回答6:

The best answer contains a small mistake: The line:

PropertiesConfigurationLayout layout = new PropertiesConfigurationLayout(config);

Must be replaced by:

PropertiesConfigurationLayout layout = config.getLayout();

回答7:

I once saw a class to do this with INI files but can't find the link anymore. If you can't find anything else, you can try DecentXML. I wrote this XML parser with the specific design goal to preserve the original formatting 100% (i.e. with comments, weird spaces in elements or around the root element, everything).

During parsing the resulting XML document, you just have to remember the elements which contain the value for your options and replace the text node in them. When you save, nothing untouched will change in any way.

来源：https://stackoverflow.com/questions/565932/a-better-class-to-update-property-files

标签

java

properties