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  1. import java.lang.invoke.CallSite;
  2. import java.lang.invoke.LambdaMetafactory;
  3. import java.lang.invoke.MethodHandle;
  4. import java.lang.invoke.MethodHandles;
  5. import java.lang.invoke.MethodType;
  6.  
  7. class Ideone {
  8.  
  9. 	public static void main(String[] args) throws Throwable {
  10. 		ISetter<TestEntity, Long> setter = getSetter(TestEntity.class, "id", Long.class);
  11.  
  12. 		TestEntity te = new TestEntity(10L);
  13. 		System.out.println(te.getId());
  14. 		setter.set(te, 15L);
  15. 		System.out.println(te.getId());
  16. 	}
  17.  
  18. 	public static <T, R> ISetter<T, R> getSetter(Class<T> clazz, String fieldName, Class<R> fieldType) throws Throwable {
  19.  
  20. 	    MethodHandles.Lookup caller = MethodHandles.lookup();
  21. 	    MethodType setter = MethodType.methodType(void.class, fieldType);
  22. 	    MethodHandle target = caller.findVirtual(clazz, computeSetterName(fieldName), setter);
  23. 	    MethodType func = target.type();
  24.  
  25. 	    CallSite site = LambdaMetafactory.metafactory(
  26. 	            caller,
  27. 	            "set",
  28. 	            MethodType.methodType(ISetter.class),
  29. 	            func.erase(),
  30. 	            target,
  31. 	            func
  32. 	    );
  33.  
  34. 	    MethodHandle factory = site.getTarget();
  35. 	    ISetter<T, R> r = (ISetter<T, R>) factory.invoke();
  36.  
  37. 	    return r;
  38. 	}
  39.  
  40. 	public static String computeSetterName(String name) {
  41. 		return "set" + Character.toUpperCase(name.charAt(0)) + name.substring(1);
  42. 	}
  43.  
  44. }
  45.  
  46. interface ISetter<T, R> {
  47.     void set(T object, R value);
  48. }
  49.  
  50. class TestEntity {
  51.  
  52.     private Long id;
  53.  
  54.  
  55.     public TestEntity(Long id) {
  56.         this.id = id;
  57.     }
  58.  
  59.  
  60.     public Long getId() {
  61.         return id;
  62.     }
  63.  
  64.     public void setId(Long id) {
  65.         this.id = id;
  66.     }
  67. }
Success #stdin #stdout 0.12s 4386816KB
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10
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https://ideone.com/KKx10r
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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