introduces TypeReference abstract class

This class permits to extract generics Type.

Author: a-peyrard

restx-common/src/main/java/restx/common/TypeReference.java

@@ -0,0 +1,38 @@
+package restx.common;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+
+/**
+ * This abstract class is used to extract generic types.
+ * <p>
+ * The {@code type} attribute hold the {@link Type} of &lt;T&gt;
+ * <p>
+ * For example if this class is used like this:
+ * <pre>
+ *     Type listStringType = new TypeReference&lt;List&lt;String&gt;&gt;() {}.getType();
+ * </pre>
+ * The {@code listStringType} will reference the type {@code List<String>}.
+ * <p>
+ * The idea is based on Gafter's blog post: <a href="http://gafter.blogspot.fr/2006/12/super-type-tokens.html?m=1">
+ *     http://gafter.blogspot.fr/2006/12/super-type-tokens.html?m=1</a>
+ *
+ *
+ * @author apeyrard
+ */
+public abstract class TypeReference<T> {
+	private final Type type;
+
+	@SuppressWarnings("unchecked")
+	protected TypeReference() {
+		Type superClass = getClass().getGenericSuperclass();
+		if (superClass instanceof Class<?>) {
+			throw new IllegalArgumentException("TypeReference must be constructed with type information.");
+		}
+		this.type = ((ParameterizedType) superClass).getActualTypeArguments()[0];
+	}
+
+	public Type getType() { return type; }
+}
+
+