adam bien's blog

Reading and Writing Configuration Files with JSON-P 📎

JSON-P ships with Java EE 8 and is already included in the API:


<dependency>
    <groupId>javax</groupId>
    <artifactId>javaee-api</artifactId>
    <version>8.0</version>
    <scope>provided</scope>
</dependency>

In standalone applications, like e.g. CLI, you will have to add the SPI (Service Provider Implementation) dependency:


<dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>javax.json</artifactId>
    <version>1.1.4</version>
</dependency>

JsonReader reads the configuration from InputStream:


    public final static String CONFIGURATION_FILE = "duke-config.json";

    public static JsonObjectBuilder load() throws FileNotFoundException {
        try (JsonReader reader = Json.createReader(new FileInputStream(CONFIGURATION_FILE))) {
            return Json.createObjectBuilder(reader.readObject());
        }
    }

and the JsonWrite serializes an in-memory instance into a stream:


    public static void write(JsonObject configuration) {
        try (JsonWriter writer = Json.createWriter(new FileOutputStream(CONFIGURATION_FILE))) {
            writer.writeObject(configuration);
        } catch (FileNotFoundException ex){}
    }

An JsonObject is a typed Map<String, JsonValue>, the values can be directly access with a key:


public static String getValue(String key) {
    JsonObject configuration = null;
    try {
        configuration = load().build();
    } catch (FileNotFoundException ex) {    }
    return configuration.getString(key);
}

jwtenizr.sh uses the above approach (see Configuration.java to store the private and public keys, issuer, as well as the JWT location.

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