Day 3 Final, with annotation examples

SimonHGR · SimonHGR · commit cc2e08ceee6e · 2021-09-10T17:54:11.000-06:00
diff --git a/src/main/java/annotations/Framework.java b/src/main/java/annotations/Framework.java
@@ -0,0 +1,29 @@
+package annotations;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+
+public class Framework {
+  public static void main(String[] args) throws Throwable {
+    System.setSecurityManager(new SecurityManager());
+    String classname = "annotations.SomeTests";
+    Class<?> theClass = Class.forName(classname);
+
+    Constructor<?> cons = theClass.getConstructor();
+    Object obj = cons.newInstance();
+
+    System.out.println("Type of created object is " + obj.getClass().getName());
+//    Method[] methods =  theClass.getMethods();
+    Method[] methods =  theClass.getDeclaredMethods();
+
+    for (Method m : methods) {
+      System.out.println("> " + m);
+      RunMe annotation = m.getAnnotation(RunMe.class);
+      if (annotation != null) {
+        System.out.println("RunMe Annotation found!!! name is " + annotation.name());
+        m.setAccessible(true);
+        m.invoke(obj);
+      }
+    }
+  }
+}
diff --git a/src/main/java/annotations/RunMe.java b/src/main/java/annotations/RunMe.java
@@ -0,0 +1,20 @@
+package annotations;
+
+//public @ interface RunMe {
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+//@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface RunMe {
+  // types of elements are strictly limited
+  // compiler must be able to "fill in" the value at compilation (i.e. from sourcecode)
+  // primitives, String, Class, other annotations (but circularity is prohibited)
+  // and arrays of the above (no multi-dimensional arrays!)
+  String name() default "Unknown";
+  int value();
+}
diff --git a/src/main/java/annotations/SomeTests.java b/src/main/java/annotations/SomeTests.java
@@ -0,0 +1,24 @@
+package annotations;
+
+//@RunMe
+public class SomeTests {
+//  @RunMe
+  String data = "hello";
+
+  @RunMe(name="Fred", value=3)
+  public void tryThis() {
+    System.out.println("running test tryThis");
+  }
+
+//  @RunMe(name="Jim")
+//  @RunMe()
+//  @RunMe(value=3)
+  @RunMe(3)
+  private void tryThat() {
+    System.out.println("Running test tryThat");
+  }
+
+  public void dontTryTheOther() {
+    System.out.println("oops, not supposed to run this");
+  }
+}
