Add some interesting new things

Adds a number of things based off of some of the notes I've made over
time, plus a few papers I've read.

More details to come later, whenever I decide to actually get serious
about documentation and examples and the like

3 files changed, 78 insertions, 0 deletions

diff --git a/base/src/main/java/bjc/utils/services/Bordello.java b/base/src/main/java/bjc/utils/services/Bordello.java
new file mode 100644
index 0000000..104c4ab
--- /dev/null
+++ b/base/src/main/java/bjc/utils/services/Bordello.java
@@ -0,0 +1,53 @@
+package bjc.utils.services;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A place to retrieve services from
+ * 
+ * @author bjcul
+ *
+ */
+public class Bordello {
+	private static final Map<Class<?>, Object> services = new ConcurrentHashMap<>();
+	
+	/**
+	 * Retrieve the implementation of a given service.
+	 * 
+	 * @param <T> The type of the service.
+	 * 
+	 * @param interfaceClass The class of the service.
+	 * 
+	 * @return The default implementation of the service.
+	 */
+	public static <T> T get(Class<T> interfaceClass) {
+		synchronized (interfaceClass) {
+			Object service = services.get(interfaceClass);
+			if (service == null) {
+				try {
+					Class<?> implementor = interfaceClass.getAnnotation(Implementor.class).value();
+					service = implementor.getDeclaredConstructor().newInstance();
+					services.put(interfaceClass, implementor);
+				} catch (Exception ex) {
+					throw new RuntimeException(ex);
+				}
+			}
+			return interfaceClass.cast(service);
+		}
+	}
+	
+	/**
+	 * Set an implementation for a given service to be something other than the default.
+	 * 
+	 * @param <T> The type of the service
+	 * 
+	 * @param interfaceClass The class of the service
+	 * @param implementor The alternate implementation for the service.
+	 */
+	public static <T> void set(Class<T> interfaceClass, T implementor) {
+		synchronized (interfaceClass) {
+			services.put(interfaceClass, implementor);
+		}
+	}
+}
diff --git a/base/src/main/java/bjc/utils/services/Implementor.java b/base/src/main/java/bjc/utils/services/Implementor.java
new file mode 100644
index 0000000..3dac860
--- /dev/null
+++ b/base/src/main/java/bjc/utils/services/Implementor.java
@@ -0,0 +1,24 @@
+package bjc.utils.services;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.*;
+
+/**
+ * Indicates the default implementation for a given service.
+ * 
+ * @author bjcul
+ *
+ */
+@Documented
+@Retention(RUNTIME)
+@Target(TYPE)
+public @interface Implementor {
+	/**
+	 * The default implementation for the service this annotates.
+	 * 
+	 * @return The default impl. for the service this annotates
+	 */
+	Class<?> value();
+}
diff --git a/base/src/main/java/bjc/utils/services/package-info.java b/base/src/main/java/bjc/utils/services/package-info.java
new file mode 100644
index 0000000..24f6855
--- /dev/null
+++ b/base/src/main/java/bjc/utils/services/package-info.java
@@ -0,0 +1 @@
+package bjc.utils.services;
\ No newline at end of file