+
+ /**
+ * 0 is the getStackTrace method 1 is the current method 2 is the parent method, 3 is the
+ * grandparent method or the parent class in this case.
+ */
+ private static final int PARENT_CLASS_INDEX = 3;
+
+
+ /**
+ * @see #readInputJson(String, Class, Class)
+ */
+ public static <T> T readInputJson(String location, Class<T> returnClass) throws IOException {
+ return readInputJson(location, returnClass, getCallingClass(PARENT_CLASS_INDEX));
+ }
+
+ /**
+ * @param location The location or name of the file we are trying to read e.g. JsonBody.json
+ * @param returnClass The class *this* Json is suppose to represent.
+ * @param locationClass The starting point for json lookup. the value specified by location is
+ * relative to this class.
+ * @return The object being returned
+ * @throws IOException Can't find the specified json file at Location.
+ */
+ public static <T> T readInputJson(String location, Class<T> returnClass, Class<?> locationClass)
+ throws IOException {
+ try (InputStream is = locationClass.getResourceAsStream(location)) {
+ validateInput(is, location);
+ return MAPPER.readValue(is, returnClass);
+ }
+ }
+
+ /**
+ * Note that this method is sensitive to the depth of the call stack. For example if a public
+ * method calls a private method, that calls this method likely the desired classIndex value is
+ * 4 rather than 3. However, it's convenient to reduce the input required by callers of this
+ * class.
+ *
+ * @param classIndex How far up the stack trace to find the class we want.
+ * @return The class that called one of the public methods of this class.
+ */
+ private static Class<?> getCallingClass(int classIndex) {
+ String className = Thread.currentThread().getStackTrace()[classIndex].getClassName();
+ try {
+ return Class.forName(className);
+ } catch (ClassNotFoundException e) {
+ // Theoretically impossible.
+ throw new IllegalStateException(
+ "Could not do class lookup for class in our stack trace?!?");
+ }
+ }
+
+ private static void validateInput(InputStream is, String location)
+ throws FileNotFoundException {
+ if (is == null) {
+ throw new FileNotFoundException(String.format("Could not find file at '%s'", location));
+ }
+ }
+