How to use Java property files?

Question

I have a list of key/value pairs of configuration values I want to store as Java property files, and later load and iterate through.

Questions:

• Do I ne

Answer 1

You can load the property file suing the following way:

InputStream is = new Test().getClass().getClassLoader().getResourceAsStream("app.properties");
        Properties props =  new Properties();
        props.load(is);

And then you can iterate over the map using a lambda expression like:

props.stringPropertyNames().forEach(key -> {
            System.out.println("Key is :"+key + " and Value is :"+props.getProperty(key));
        });

Answer 2

If you put the properties file in the same package as class Foo, you can easily load it with

new Properties().load(Foo.class.getResourceAsStream("file.properties"))

Given that Properties extends Hashtable you can iterate over the values in the same manner as you would in a Hashtable.

If you use the *.properties extension you can get editor support, e.g. Eclipse has a properties file editor.

Answer 3

In order:

1. You can store the file pretty much anywhere.
2. no extension is necessary.
3. Montecristo has illustrated how to load this. That should work fine.
4. propertyNames() gives you an enumeration to iterate through.

Answer 4

Reading a properties file and loading its contents to Properties

String filename = "sample.properties";
Properties properties = new Properties();

input = this.getClass().getClassLoader().getResourceAsStream(filename);
properties.load(input);

The following is the efficient way to iterate over a Properties

    for (Entry<Object, Object> entry : properties.entrySet()) {

        System.out.println(entry.getKey() + " => " + entry.getValue());
    }

Answer 5

In Java 8 to get all your properties

public static Map<String, String> readPropertiesFile(String location) throws Exception {

    Map<String, String> properties = new HashMap<>();

    Properties props = new Properties();
    props.load(new FileInputStream(new File(location)));

    props.forEach((key, value) -> {
        properties.put(key.toString(), value.toString());
    });

    return properties;
}

Answer 6

Here is another way to iterate over the properties:

Enumeration eProps = properties.propertyNames();
while (eProps.hasMoreElements()) { 
    String key = (String) eProps.nextElement(); 
    String value = properties.getProperty(key); 
    System.out.println(key + " => " + value); 
}