101companies

Headline

Processing JSON with the Jackson DataBinding API using a JsonTree representation

Characteristics

This contribution process a company saved in a JSON-file to JsonTree representation. It performs the Features Total , Cut ,Parsing and Unparsing, to demonstrate how to use a JsonTree from Jackson.

Illustration

This contribution uses a ObjectMapper for parsing and unparsing. The mapper provides methods to easily map between most kinds of Java object and a JSON file. In this case the mapper maps the JSON to a JsonTree. 

public static JsonNode parseFromFile(File file) {
    ObjectMapper mapper = new ObjectMapper();
    JsonNode root = null;
    try {
        root = mapper.readTree(file);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return root;
}
A JsonTree is build of JsonNodes, which can be simple key-value pairs, JSON objects or JSON arrays.

A part from the total method as a simple example to demonstrate how to search for certain values: 

    if (node.get("salary") != null)
        return node.get("salary").asDouble();
    else {
        if (node.has("departments")) {
            Iterator<JsonNode> iterator = node.path("departments").elements();
            while (iterator.hasNext()) {
                result += total(iterator.next());
            }
        }
        if (node.has("employees")) {
            Iterator<JsonNode> iterator = node.path("employees").elements();
            while (iterator.hasNext()) {
                result += total(iterator.next());
            }
        }
    }
The class Unparsing used a ObjectWriter to prettyprint the tree to its JSON representation. 
    ObjectMapper mapper = new ObjectMapper();
    PrettyPrinter printer = new DefaultPrettyPrinter();
    ObjectWriter writer = mapper.writer(printer);

Usage

Use Gradle to build this contribution. For running and editing this contribution supports Eclipse.

See https://github.com/101companies/101simplejava/blob/master/README.md

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