refactoring plugin api

 - redefine Interceptor type

bootstrap-core/src/main/java/com/navercorp/pinpoint/bootstrap/instrument/InstrumentClass.java

@@ -48,7 +48,7 @@ public interface InstrumentClass {
     ClassLoader getClassLoader();
 
 
-    public boolean isInterceptable();
+    boolean isInterceptable();
 
     boolean hasConstructor(String... parameterTypes);
 

bootstrap-core/src/main/java/com/navercorp/pinpoint/bootstrap/interceptor/InterceptorInvokerHelper.java

@@ -29,7 +29,7 @@ public static void handleException(Throwable t) {
         if (propagateException) {
             throw new RuntimeException(t);
         } else {
-            logger.warn("Excetpion occured from interceptor", t);
+            logger.warn("Exception occurred from interceptor", t);
         }
     }
 

bootstrap-core/src/main/java/com/navercorp/pinpoint/bootstrap/interceptor/SpanAsyncEventSimpleAroundInterceptor.java

@@ -19,6 +19,13 @@ public abstract class SpanAsyncEventSimpleAroundInterceptor implements AroundInt
     final MethodDescriptor asyncMethodDescriptor = new AsyncMethodDescriptor();
 
     public SpanAsyncEventSimpleAroundInterceptor(TraceContext traceContext, MethodDescriptor methodDescriptor) {
+        if (traceContext == null) {
+            throw new NullPointerException("traceContext must not be null");
+        }
+        if (methodDescriptor == null) {
+            throw new NullPointerException("methodDescriptor must not be null");
+        }
+
         this.traceContext = traceContext;
         this.methodDescriptor = methodDescriptor;
 

bootstrap-core/src/main/java/com/navercorp/pinpoint/bootstrap/interceptor/SpanEventSimpleAroundInterceptorForPlugin.java

@@ -35,6 +35,12 @@ public abstract class SpanEventSimpleAroundInterceptorForPlugin implements Aroun
     protected final TraceContext traceContext;
 
     protected SpanEventSimpleAroundInterceptorForPlugin(TraceContext traceContext, MethodDescriptor descriptor) {
+        if (traceContext == null) {
+            throw new NullPointerException("traceContext must not be null");
+        }
+        if (descriptor == null) {
+            throw new NullPointerException("descriptor must not be null");
+        }
         this.traceContext = traceContext;
         this.methodDescriptor = descriptor;
     }