Question

I want to make a bean which has values from properties file. I made something like this:

@Component
public class MainNavs implements Iterable<Nav>{
    @Value("${newshome.navs.names}")
    String[] names;

    @Value("${newshome.navs.ids}")
    String[] ids;

    final private List<Nav> navs = new ArrayList<Nav>();

    public MainNavs() throws Exception {            
        for (int i = 0; i < names.length; i++) {
            navs.add(new Nav(names[i], ids[i]));
        }
    }

    public Iterator<Nav> iterator() {
        Iterator<Nav> n = navs.iterator();
        return n;
    }

    public class Nav {      
        private String name;
        private String id;
        private String imageNumber;

        public Nav(String name, String id, String imageNumber) {
            this.name = name;
            this.id = id;
        }

        //....
    }
}

But when I autowire like this @Autowired MainNavs navs;, it makes NullPointerException because the names and ids were not initiated when it try to access those in constructor.

If I made some method like init() and tried to initiate with it, there wasn’t any problem.

public init() throws Exception {            
    for (int i = 0; i < names.length; i++) {
        navs.add(new Nav(names[i], ids[i]));
    }
}

However, I don’t want initiate manually. Can I initiate it in constructor? Or any other alternatives?

Answer 1

Use @PostConstruct on your init() method – it will be called by spring as soon as the object is inside the spring context, which means all if its dependencies will be injected.