Check nested Java objects for null

Question

I have nested JAXB object which I would like to check for null.

if(message.getMpiParams() != null & 
        message.getMpiParams().getOne() != null &
        message.getMpiParams().getTwo() != null &
        message.getMpiParams().getThu() != null) { 

        ...// a lot of methods here

    }

When the inner object is empty I get always NPE. This is because XML tags are missing. How I can check for missing inner object safely without NPE? I just want to check for null object.

JAXB Object:

@XmlRootElement(name = "message")
@XmlAccessorType(XmlAccessType.FIELD)
public class Message{

    @XmlElement(name = "mpi_params")
    public MpiParams mpiParams; 

}

@XmlAccessorType(XmlAccessType.FIELD)
public class MpiParams {

    @XmlElement(name = "one")
    public String one;
}

What do you mean "When the inner object is empty I get always NPE."? What inner object? Please show code that will cause an NPE in such a case. The code you show here will only throw NPE if `message` itself is `null`. — Code-Apprentice, Oct 04 '19 at 21:21
I men when for example inner XML `mpi_params` is missing I get NPE. Post is updated. — Peter Penzov, Oct 04 '19 at 21:26
Your null check is fine, your operator usage isn't. See the linked question. — Tom, Oct 04 '19 at 21:28
Is there some way to do this with Java 8 Streams or Otional? — Peter Penzov, Oct 04 '19 at 21:36

score -2 · Answer 1 · answered Oct 04 '19 at 21:25

-2

Try changing

if(message.getMpiParams() != null

with

if(!(message.getMpiParams().equals(null))

answered Oct 04 '19 at 21:25

Ithil Maethor

59
1
7

3

When do you expect `.equals(null)` to become true? – Tom Oct 04 '19 at 21:29
It's OK to perform null checks with != – fps Oct 04 '19 at 21:31

Check nested Java objects for null

1 Answers1