Change values and then save it in the config.

[spideynn]

Hi,
Is it possible to change the config value while the application is running and then save the config with the changed value? (If it is then I didn't see it in the docs)

[lviggiano]

Hi.

This use case can be covered by Accessible and Mutable interfaces.

To change properties of a Config object, you can use the Mutable interface.

Example:

     public interface MyConfig extends Config, Mutable {
         @DefaultValue("18")
         int minAge();
     }

     public void example() {
         MyConfig cfg = ConfigFactory.create(MyConfig.class);
         int before = cfg.minAge();                 // before = 18
         int old = cfg.setProperty("minAge", "21"); // old = 18
         int after = cfg.minAge();                  // after = 21
         int old2 = cfg.removeProperty("minAge");   // old2 = 21
         int end = cfg.minAge();                    // end = null
     }

Once the cfg object is updated in memory you can dump it to the filesystem using method store() exposed by the Accessible interface

Some time ago, someone asked a "smart properties save method" (see #16), unfortunately it is not easy to implement it properly.

Alternatively...

If your properties file is stored on the file system you could change the properties file (something like this), then you use the hot reload feature to have your object automatically updated. Unfortunately this use case is not available inside the library yet, so you have to implement it by your own.

[zygimantus]

I found an easy solution like this:

ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
URL url = classLoader.getResource("Config.properties");
onfig.store(new FileOutputStream(url.getFile()), "no comments");