reading files & caching

[Vinnie Jenks]

I just built a class that will read a .properties file and get values from it. Since I'll be making frequent calls to this for configuration values throughout my app, how can I cache access to this file so I'm not reading the entire file on every call?

Would I need to do this?

Here's the class:

public class Property
{
protected Properties props;

public Property()
{
if (this.props == null)
{
this.props = new Properties();
this.getAllProperties();
}
}

private void getAllProperties()
{
try
{
//top level configuration directory
File propsDir = new File("C:\\MyApp\\config\\");

//create if missing
if (!propsDir.exists())
propsDir.mkdirs();

//properties file
File propsFile = new File(propsDir.getAbsolutePath() + "myapp.properties");

//create if missing
if (!propsFile.exists())
propsDir.createNewFile();

FileInputStream fiStream = new FileInputStream(propsFile.getAbsoluteFile());
this.props.load(fiStream);
}
catch (FileNotFoundException e)
{
// TODO Use custom error-handling!
e.printStackTrace();
}
catch (IOException ioe)
{
// TODO Use custom error-handling!
ioe.printStackTrace();
}
}
}

I created another class which extends Property (above):

public class PropertiesProxy extends Property
{
public PropertiesProxy()
{
}

public String getImagesPath()
{
return this.props.getProperty("imagepath");
}

public String smtpServer()
{
return this.props.getProperty("smtpserver");
}
}

In my app I'd then make calls to those methods when needed. Won't I be adding some real overhead by constantly calling & reading this file?

Advice is much appreciated, thanks!

-v

[Jeff Albertson]

Why not just define your class as a Singleton?

[pascal betz]

dont use absolute file paths. use relative file paths or even better load the properties as a resource from classpath.

if you need frequent access to these properties then just keep a reference to it and pass it to the dependent objects.


pascal

[Stan James]

I wrote a properties cache for my first Java project. It has a map keyed on filename and each entry in the map is a collection of properties. It reads all the properties files in a list of directories into cache in a single call. For server apps I always have a management API that lets me clear and reload one or all files in the cache. It looks something like ...

String prop = Properties.getProperty( fileName, propertyName );

[Peter Chase]

This is a good opportunity to use SoftReference. If you store your cache of Properties in a SoftReference, then Java will delete your cache automatically, in a low-memory situation. That's fine, because the cache contents can be recreated from the Properties files at any time. By using SoftReference, you can stop worrying about whether your cache is getting too big.