Gradle: Read property from file

build.gradle

/**
 * Read property with {@code propertyName} from file with {@code fileName}.
 * <p>
 * Example of property file content:<br>
 * api_key=5c7f743fe85eae73489af35c1a387a05
 * apiSecret=12345678910
 *
 * @return Value of specified property.
 * @throws GradleException if file not found or there is no specified property in a file.
 */
def property(String fileName, String propertyName) {
    def propsFile = rootProject.file(fileName)
    if (propsFile.exists()) {
        def props = new Properties()
        props.load(new FileInputStream(propsFile))
        if (props[propertyName] != null) {
            return props[propertyName]
        } else {
            throw new GradleException("There is no '" + propertyName + "' property in '" + propsFile.name + "' file")
        }
    } else {
        throw new GradleException("'" + propsFile.name + "' file does not exist")
    }
}