code: public void merge(Dependency parentDefined) {
          if(optional == null ){
              setOptional(parentDefined.isOptional());
          }
          if(version == null){
              setVersion(parentDefined.getVersion());
          }
          if(classifier == null ){
              setClassifier(parentDefined.getClassifier());
          }
          if(scope == null ){
              setScope(parentDefined.getScope());
          }
          if(exclusions == null ){
              setExclusions(parentDefined.getExclusions());
          }
      }
docs: 为某个依赖补齐信息
  @param parentDefined 父组件中定义的依赖信息