Is there a way to check if a class is empty in java?-CodePudding

Sorry if the title is a bit confusing, I didn't really know how to word what I wanted to ask.

Basically, I am making an api call to a database that returns data as such:

[{"profiles":{"testexample":{"addresses":[{"city":"","street1":"","street2":"apt 320"}],"addressType":"HOME","city":"","dateOfBirth":"","emailAddress1":"","emailAddress2":"","emailAddresses":[{"email":"","preferred":1,"type":"BUSINESS"},{"email":"","preferred":0,"type":"PERSONAL"}],"firstName":"","lastName":"","phoneNumber":"","phoneNumbers":[],"phoneType":"HOME","postalCode":"","preferred":1,"street1":"","street2":""}]

The code I have below works fine when the database returns a non-empty profiles {}. I have the following Java classes that looks like the following:

public class Account {

    @JsonProperty("profiles")
    private Profiles profiles;

    @JsonProperty("profiles")
    public Profiles getProfiles() {
        return profiles;
    }

    @JsonProperty("testexample")
    public void setProfiles(Profiles profiles) {
        this.profiles = profiles;
    }

}

public class Profiles {

    @JsonProperty("testexample")
    private Profile testExample;

    @JsonProperty("testexample")
    public Profile getTestExample() {
        return testExample;
    }

    @JsonProperty("testexample")
    public void setTestExample(Profile testExample) {
        this.testExample = testExample;
    }

}

public class Profile {


    @JsonProperty("dateOfBirth")
    private String dateOfBirth;

    @JsonProperty("dateOfBirth")
    public String getDateOfBirth() {
        return dateOfBirth;
    }
    @JsonProperty("dateOfBirth")
    public void setDateOfBirth(String dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

}

So what I want to do when I get the data is check whether the getProfiles() returns empty, so I don't make the calls to anything within that object.

Please note, for the sake of simplicity I omitted other parts of the classes to focus primarily on what I wanted

This is what I have so far, and it works when the profiles {} is not empty

Account response = access.lookup(id, type); //This is to grab the response from the database, which is working.

response.getProfiles(); //This is the part that works when it has a profiles {} not empty, but fails on empty.

So what happens is that I don't get an error for response.getProfiles(), but if I tried to do response.getProfiles().getDateOfBirth(), it won't work because it will give a null pointer exception since the dateOfBirth isn't there.

I want to avoid calling anything within response.getProfiles() by skipping it if it's empty.

CodePudding user response：

You need some basic null checking. The most basic way is to assign a new variable and check.

Profiles profiles = account.getProfiles();
if(profiles != null) {
   //dosomething with profiles.getDateOfBirth()
}

The more "modern" functional Java way would be to use the Optional class.

String dateOfBirth = Optional.ofNullable(account.getProfiles())
    .map(profile -> profile.getDateOfBirth)
    .orElse(null);

(A note about your example: In the Account class, you have this.

@JsonProperty("testexample")
public void setProfiles(Profiles profiles) {
    this.profiles = profiles;
}

Which appears to be an incorrect @JsonProperty annotation and might be causing some problems. That said, it is not necessary to annotate the getters and setters. The one annotation on the field is sufficient.)