How to read property file values into set of Strings in Spring boot

Question

I have tried using

@Value("#{'${white.listed.hotel.ids}'.split(',')}")
private Set<String> fareAlertwhiteListedHotelIds;

but When white.listed.hotel.ids is empty then also set has one size with blank value.

white.listed.hotel.ids =

Can someone pls help me with a version in which whiteListedHotelIds can contain either values if specified in property file or has no item for blank case.

do you mean specifying a default value in case whiteListedHotelIds is empty ? — AchillesVan, Oct 23 '16 at 14:46
possible duplicate of http://stackoverflow.com/questions/11991194/can-i-set-null-as-the-default-value-for-a-value-in-spring — Saravana, Oct 23 '16 at 14:57
@Georgesvanhoutte van houtte : I just wanted the set to be Empty in case whiteListedHotelIds is Empty. — ankita gupta, Oct 23 '16 at 18:38

score 5 · Accepted Answer · edited May 23 '17 at 12:06

5

You can call a custom method (as described in this other answer to build a map, itself inspired by @FedericoPeraltaSchaffner's answer):

@Value("#{PropertySplitter.toSet('${white.listed.hotel.ids}')}")
private Set<String> fareAlertwhiteListedHotelIds;

...

@Component("PropertySplitter")
public class PropertySplitter {
    public Set<String> toSet(String property) {
        Set<String> set = new HashSet<String>();

        //not sure if you should trim() or not, you decide.
        if(!property.trim().isEmpty()){
            Collections.addAll(set, property.split(","));
        }

        return set;
    }
}

In this method, you are free to handle the property as you wish (for instance a particular logic when empty).

edited May 23 '17 at 12:06

Community

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answered Oct 23 '16 at 15:31

alexbt

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Or `Collections.addAll(set, property.split(","));` skipping the intermediate `List` step. – Holger Oct 24 '16 at 10:36
Thanks @Holger! I've replaced Arrays.asList(...) with your suggestion! – alexbt Oct 24 '16 at 10:38

Ryuzaki L · Answer 2 · 2020-04-20T02:50:14.477

1

You can use the spring expression language for validation as well, if the provided string is empty then return empty array or split input string into array. From jdk-11 you can use isBlank directly

@Value("#{'${white.listed.hotel.ids}'.trim().isEmpty() ? new String[] {} : '${white.listed.hotel.ids}'.split(',')}")
private Set<String> fareAlertwhiteListedHotelIds;

edited Apr 20 '20 at 02:50

answered Apr 20 '20 at 02:44

Ryuzaki L

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score 0 · Answer 3 · answered Oct 24 '16 at 21:10

Inject @Value through constructor (as you always should) and do all post-processing you need there:

@Component
class Foo {
    private final List<String> bar;

    public Foo(@Value("${foo.bar}") List<String> bar) {
        this.bar = bar.stream()
                      .filter(s -> !"".equals(s))
                      .collect(Collectors.toList());
    }
}

There is no need to complicate things with SPEL.

How to read property file values into set of Strings in Spring boot

3 Answers3