Add empty judgment for constructorInterceptPoint (#732)

Author: CodePrometheus

CHANGES.md

@@ -12,6 +12,7 @@ Release Notes.
 * Add async-profiler feature for performance analysis 
 * Support db.instance tag,db.collection tag and AggregateOperation span for mongodb plugin(3.x/4.x)
 * Improve CustomizeConfiguration by avoiding repeatedly resolve file config
+* Add empty judgment for constructorInterceptPoint
 
 All issues and pull requests are [here](https://github.com/apache/skywalking/milestone/222?closed=1)
 

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/interceptor/enhance/ClassEnhancePluginDefine.java

@@ -112,17 +112,20 @@ protected DynamicType.Builder<?> enhanceInstance(TypeDescription typeDescription
          */
         if (existedConstructorInterceptPoint) {
             for (ConstructorInterceptPoint constructorInterceptPoint : constructorInterceptPoints) {
+                String constructorInterceptor = constructorInterceptPoint.getConstructorInterceptor();
+                if (StringUtil.isEmpty(constructorInterceptor)) {
+                    throw new EnhanceException("no InstanceConstructorInterceptor define to enhance class " + enhanceOriginClassName);
+                }
                 if (isBootstrapInstrumentation()) {
                     newClassBuilder = newClassBuilder.constructor(constructorInterceptPoint.getConstructorMatcher())
-                                                     .intercept(SuperMethodCall.INSTANCE.andThen(MethodDelegation.withDefaultConfiguration()
-                                                                                                                 .to(BootstrapInstrumentBoost
-                                                                                                                     .forInternalDelegateClass(constructorInterceptPoint
-                                                                                                                         .getConstructorInterceptor()))));
+                            .intercept(SuperMethodCall.INSTANCE.andThen(MethodDelegation.withDefaultConfiguration()
+                                    .to(BootstrapInstrumentBoost
+                                            .forInternalDelegateClass(constructorInterceptor))));
                 } else {
                     newClassBuilder = newClassBuilder.constructor(constructorInterceptPoint.getConstructorMatcher())
-                                                     .intercept(SuperMethodCall.INSTANCE.andThen(MethodDelegation.withDefaultConfiguration()
-                                                                                                                 .to(new ConstructorInter(getPluginName(), constructorInterceptPoint
-                                                                                                                     .getConstructorInterceptor(), classLoader), delegateNamingResolver.resolve(constructorInterceptPoint))));
+                            .intercept(SuperMethodCall.INSTANCE.andThen(MethodDelegation.withDefaultConfiguration()
+                                    .to(new ConstructorInter(getPluginName(), constructorInterceptor, classLoader),
+                                            delegateNamingResolver.resolve(constructorInterceptPoint))));
                 }
             }
         }