Question

I’m new for both Sonar and Weld/CDI. I would like your help to advise further about the LCOM4 analyzed result with Weld/CDI. Firstly I create a simple java class as the following: –

————-Source—————

interface MyInterface1 {
   String getName();
   void setName(String name);
}

interface MyInterface2 extends MyInterface1 {
   String getPhone();
   void setPhone();
}

public interface MyPublishedInterface extend MyInterface1, MyInterface2 {
   //There is no any definition, it just a collected capabilities 
   //which will be published to other package. Some capabilities 
   //may be hidden and use internally.
}

abstract class MyBean1 implements MyInterface1 {
   private String name;
   @Override
   public String getName() {
      return this.name;
   }
   @Override
   public void setName(String theName) {
      this.name = theName;
   }
}

abstract class MyBean2 extends MyBean1 implements MyInterface2 {
   private String phone;
   @Override
   public String getPhone() {
      return this.phone;
   }
   @Override
   public void setPhone(String thePhone) {
      this.phone= thePhone;
   }
}

public class MyPublishedBean extends MyBean2 implements MyPublishedInterface {
   //There is no any coding, it just a collected capabilities 
   //which will be published to other package. Some capabilities
   //may be hidden and use internally.
}

@Named
@RequestScope
public class MyBackingBean {
   @Inject
   private MyPublishedInterface myPublishedInterface;

   //-----the business method, setter and getter here.
}

————-Source—————

After I’ve analyzed with the Sonar, it reports that the MyPublishedBean has a LCOM4>1 as

1. getPhone()Ljava/lang/String;
2. setName(Ljava/lang/String;)V
3. setPhone(Ljava/lang/String;)V
4. getName()Ljava/lang/String;

Previously I used to mark all method to be a “final” method, there is no any mentions about the LCOM4. Anyhow the system shows me the exception about Unproxyable since my class contains a final method. I had removed the “final”, I faced the LCOM4 issue.

I’m not sure if I’m confused about Sonar, Weld/CDI, the class/interface design or all of them. Could you please help to advise further?

Answer 1

The Sonar docs explain LCOM4 quite well. The results you see are completely correct given the example you gave here.

These interfaces look like they are merely data holders with no logic. A bean with just getters and setters for properties will fully expect to have an LCOM value equal to the number of properties in the bean. LCOM4 is a metric meant to measure the cohesion of logic in a class. The logic of a pure data bean is only that the data is in some way related to each other. LCOM4 is therefore in this case an incorrect and misleading metric to use.

LCOM4 should also be completely independent of whether your methods are final or not.

Please note that LCOM4 > 1 indicates a suspect class. It does not mean that the class is wrong and should not be used to flag the class as bad. Once you find that the suspect class is okay, it is best to remove that class in some way from the metric (to avoid you building up a long list of warnings that you know should be ignored).