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  1. import java.lang.annotation.ElementType;
  2. import java.lang.annotation.Retention;
  3. import java.lang.annotation.RetentionPolicy;
  4. import java.lang.annotation.Target;
  5. import java.lang.reflect.Field;
  6. import java.lang.reflect.Modifier;
  7. import java.util.HashMap;
  8. import java.util.Map;
  9.  
  10. @Retention(RetentionPolicy.RUNTIME)
  11. @Target(ElementType.FIELD)
  12. @interface PatternHandler {
  13.     String value();
  14. }
  15.  
  16. interface TownyChatReplacerCallable {
  17.     String call(String match, String event);
  18. }
  19.  
  20. class AnnotationRegistry {
  21.     private static final Map<String, TownyChatReplacerCallable> MAP = new HashMap<String, TownyChatReplacerCallable>();
  22.     public static void register(String pattern, TownyChatReplacerCallable handler) {
  23.         System.out.println("Registering pattern:" + pattern + " handler:" + handler);
  24.         MAP.put(pattern, handler);
  25.     }
  26.     public static void handle(String pattern, String event) {
  27.         TownyChatReplacerCallable handler = MAP.get(pattern);
  28.         if (handler != null) {
  29.             String result = handler.call(pattern, event);
  30.             System.out.println("Handler returned:" + result);
  31.         } else {
  32.             System.out.println("No Handler for:" + pattern);
  33.         }
  34.     }
  35.  
  36.     public static void register(Class<?> clazz) {
  37.         Field[] fields = clazz.getDeclaredFields();
  38.         for (Field field : fields) {
  39.             PatternHandler annotation = field.getAnnotation(PatternHandler.class);
  40.             if (annotation != null) {
  41.                 if (!Modifier.isStatic(field.getModifiers())) {
  42.                     System.out.println("Field must be static:" + field.getName());
  43.                     continue;
  44.                 }
  45.                 try {
  46.                     Object object = field.get(null);
  47.                     if (object instanceof TownyChatReplacerCallable) {
  48.                         register(annotation.value(), (TownyChatReplacerCallable) object);
  49.                     } else {
  50.                         System.out.println("Field must be instanceof TownyChatReplacerCallable:"  + field.getName());
  51.                     }
  52.                 } catch (IllegalArgumentException e) {
  53.                     e.printStackTrace();
  54.                 } catch (IllegalAccessException e) {
  55.                     e.printStackTrace();
  56.                 }
  57.             }
  58.         }
  59.     }
  60. }
  61.  
  62. class Callables {
  63.  
  64.     @PatternHandler("foo")
  65.     public static final TownyChatReplacerCallable FOO = new TownyChatReplacerCallable() {
  66.         @Override
  67.         public String call(String match, String event) {
  68.             return "This is foo handler called with " + match + "," + event;
  69.         }
  70.     };
  71.  
  72.     @PatternHandler("bar")
  73.     public static final TownyChatReplacerCallable BAR = new TownyChatReplacerCallable() {
  74.         @Override
  75.         public String call(String match, String event) {
  76.             return "This is foo handler called with " + match + "," + event;
  77.         }
  78.     };
  79.  
  80.     @PatternHandler("lala")
  81.     public static final String WRONG_CLASS = "";
  82.  
  83.     @PatternHandler("lulu")
  84.     public final TownyChatReplacerCallable notStatic = new TownyChatReplacerCallable() {
  85.         @Override
  86.         public String call(String match, String event) {
  87.             return "This is foo handler called with " + match + "," + event;
  88.         }
  89.     };
  90. }
  91.  
  92. public class Main {
  93.     public static void main(String[] args) {
  94.         AnnotationRegistry.register(Callables.class);
  95.  
  96.         System.out.println("\n-- Done with registration --\n");
  97.  
  98.         AnnotationRegistry.handle("foo", "event1");
  99.         AnnotationRegistry.handle("bar", "event2");
  100.         AnnotationRegistry.handle("zoom", "event3");
  101.     }
  102. }
  103.  
Success #stdin #stdout 0.09s 380352KB
comments (?)
stdin 
Standard input is empty
stdout 
Registering pattern:foo handler:Callables$1@157011e
Registering pattern:bar handler:Callables$2@10a8143
Field must be instanceof TownyChatReplacerCallable:WRONG_CLASS
Field must be static:notStatic

-- Done with registration --

Handler returned:This is foo handler called with foo,event1
Handler returned:This is foo handler called with bar,event2
No Handler for:zoom
https://ideone.com/m3PPcY
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
secret

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