FactoryBean with @Value in constructor?

Question

Is is possible to add a non-empty default constructor to a FactoryBean, where the parameter is injected by @Value?

@Service
public class DateTimeFormatterFactory implements FactoryBean<DateTimeFormatter> {
    private DateTimeFormatter formatter;

    @Autowired
    public DateTimeFormatterFactory(@Value("${custom.format}") String format) {
        formatter = DateTimeFormatter.ofPattern(format);
    }

    @Override
    public DateTimeFormatter getObject() {
        return formatter;
    }

    @Override
    public Class<?> getObjectType() {
        return DateTimeFormatter.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

/edit: I should have added the error message. Spring complains that there is not "default" constructor without arguments. But if I add one, then my @Value constructor is never called...

yes :) it is... but are you aware there is a property for that **spring.mvc.date-format** (assume you use spring-boot) — Dirk Deyne, Apr 30 '18 at 14:16
As far as I know, it should work just like that. Where is the problem here? — Link64, Apr 30 '18 at 14:18

DwB · Accepted Answer · 2018-05-01T13:16:55.080

1

Yes, but you don't need a constructor parameter for this.

Instead, you can create a PostConstruct method and initialize the formatter therein.

For example,

@Value("${custom.format}")
private String desiredDateFormat;

@PostConstruct
public void postConstruct()
{
    formatter = DateTimeFormatter.ofPattern(desiredDateFormat);
}

Option 2 (A.K.A response to comment)

If you only need the value to create the DateTimeFormatter, then just use it to create the DateTimeFormatter in a "setter-like" method that I will call a "settee" (because I don't know what to actually call it). Here is some code:

@Value("${custom.format}")
public void createDateTimeFormatter(
    final String desiredDateFormat)
{
    formatter = DateTimeFormatter.ofPattern(desiredDateFormat);
}

edited May 01 '18 at 13:16

answered Apr 30 '18 at 14:25

DwB

37,124
11
56
82

The drawback is that I'd have to introduce an extra variable for the `@Value` injection that is afterwards never used again. I tend to avoid variables that are only used once... – membersound May 01 '18 at 07:13
Option 2 is derived from the @Bartosz Bilicki answer to this question: https://stackoverflow.com/questions/33562731/spring-autowire-property-vs-setter – DwB May 01 '18 at 13:19
Having the `@Value` on top of the setter (instead on the parameter) worked. That's what I was looking for! – membersound May 02 '18 at 11:12

FactoryBean with @Value in constructor?

1 Answers1