Ways to replace apache.commons.configuration in your project

If you’re using apache.commons.configuration to manage .properties files in your project, you’re probably facing the following problem: Apache.commons.configuration depends on apache.common.logging which is included in maven:3.5, but was removed from maven:3.6. Thus, if you want to upgrade you will need to find a different way to parse your properties.

Java offers the java.util.Properties class, which is a subclass of java.util.Hashtable. It maintains a list of keys and values, both are of type String, and provides methods for the following operations: Loading and saving the properties, getting a value by key, listing the keys and values, enumerating over the keys, and the methods inherited from the Hashtable class.

But what if our data is complex? #

If we have nested properties (i.e food.apple=red, food.icecream=vanilla, drink.milk=soy, drink.soft=coke) how will we find all of the information about the main key (food, in this example)? In order to retrieve the complete value we will need to iterate over the entire Hashtable, searching for all of the keys that contain food..

Here comes the biggest advantage of using apache.commons.configuration- It offers a generic configuration interface to read data from a variety of sources, and access to single and multi-valued configuration parameters.

When I started working on removing the dependency on apache.commons.configuration, I figured that since the properties we use are nested, I should see which methods of apache.commons.configuration we are actually using, and then I tried to mimic the original implementation. It was very tricky as I faced a whole chain of inheritance and interfaces to implement. After already putting some work into it, I decided to drop it all and go with a different approach. The main thing I had to handle was being able to set the nested properties properly. I decided to save the properties into a HashMap that stores String for the key, and JsonNode for the value. That way I could set and get each property by its main key easily, and get the specific data of a specific secondary key if needed. For other operations I used the HashMap’s builtin methods.

Here’s a snippet of my implementation for storing the data from the .properties file, where I used com.fasterxml.jackson for handling the JsonNode:

private void populateProperties(File file) throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    List lines = Files.readAllLines(file.toPath());
    Map<String, String> allProps = new HashMap<>();
    for (String line: lines) {
        if (line.contains("=")) {
            allProps.put(line.split("=")[0], line.split("=")[1]);
        }
    }
    allProps.forEach((k, v) -> {
        String[] mainKey = k.split("\\.");
        if (this.props.get(mainKey[0]) != null) {
            JsonNode oldNode = this.props.get(mainKey[0]);
            ((ObjectNode) oldNode).put(mainKey[1], v);
            this.props.put(mainKey[0], oldNode);
        } else {
            ObjectNode node = mapper.createObjectNode();
            node.put(mainKey[1], v);
            this.props.put(mainKey[0], node);
        }
    });
}

When choosing to use this implementation, we need to handle the case of an IO Exception. That is a small price compared to the convenience of maintaining the nested properties in a simple format.

To conclude, if you need to replace apache.commons.configuration, you can either use Java’s Properties class, or decide on your own implementation — preferably use a data structure to handle your .properties file.
Each method has its own drawbacks.
Using the Properties class will be most suitable for simple key-value pairs, while for nested data I’d recommend using a data structure where the key stores the main key, and the value will hold a JsonNode that will store the secondary keys and their values.