Injecting array of values from properties file in spring boot

Question

Ok, so i have a config.properties ..:

market.curpairs[0].name=EuroDollar
market.curpairs[0].symbol=EURUSD
market.curpairs[0].minamount=0.1
market.curpairs[1].name=EuroFranken
market.curpairs[1].symbol=EURCHF
market.curpairs[1].minamount=0.1
market.currs[0].name=Euro
market.currs[0].symbol=EUR
market.currs[0].minamount=1.0
market.currs[0].withfee=0.1
market.currs[1].name=Dollar
market.currs[1].symbol=USD
market.currs[1].minamount=1.0
market.currs[1].withfee=0.1
market.currs[2].name=Franken
market.currs[2].symbol=CHF
market.currs[2].minamount=1.0
market.currs[2].withfee=0.1

which i then attempt to inject into MarketConfig.java like this:

@PropertySource("classpath:config.properties")
@ConfigurationProperties(prefix = "market")
@Validated
public class MarketConfig {

    // the configured currencies
    private List<MarketCurrency> currs;

    // the configured currencypairs
    private List<MarketCurrencypair> curpairs;

  /* static classes */
  public static class MarketCurrency {
    String name;
    String symbol;
    double minamount;
    // getter and setter ommitted
  }
  public static class MarketCurrencypair {
    String name;
    String symbol;
    double minamount;
    double withfee;
    // getter and setter ommitted
  }
  // getter and setter ommitted
}

..which then is used in MarketService.java:

 @Service
    public class MarketService implements IMarketService {

        private final MarketConfig config;

        // ....

         public MarketService(MarketConfig config) {
            this.config = config;
         }
        // ....
        public void printConfig() {
           System.out.println("________________ CONFIGURATION: ");
           this.config.getCurpairs().forEach(System.out::println);
           this.config.getCurrs().forEach(System.out::println);
        }
    }

...which is called by the Applicationmain:

@SpringBootApplication
@EnableSwagger2
@ComponentScan
@EnableConfigurationProperties({MarketConfig.class})
public class MarketApplication implements CommandLineRunner {

    private final MarketService service;

    /**
     * Constructor
     * @param service  ..the Service
     */
    public MarketApplication(MarketService service) {
        this.service = service;
    }

    public static void main(String[] args) {
        SpringApplication.run(MarketApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        this.service.printConfig();
    }
}

...yielding me NullPointerException

Caused by: java.lang.NullPointerException: null
    at forex.market.service.MarketService.printConfig(MarketService.java:67) ~[classes/:na]

Q1: Am i doing it right, basically?

Q2: I couldn't find any help on the internet how to handle arrays of primitive-tuples in properties files, is it even possible to inject that into a spring-boot configuration - or do i need to rewrite my config to strings, using split() to acquire the individual values (which i really don't want to for the sake of maintainability and readability) ?

Thanks in advance - if you miss out some information/source, please comment, i will supply it shortly.

Answer 1

you need to set your property-prefix don't need @Configuration and @Component and use embedded public static class to wrap properties of the currency

 @PropertySource("classpath:config.properties")
 @ConfigurationProperties(prefix = "market")
 @Validated
 public class MarketConfig {
      List<MarketCurrency> currs;
      //getters setters

      public static class MarketCurrency {

          String name;
          String symbol;
        ....
//getters setters

add MarketConfig.class to @EnableConfigurationProperties

 @SpringBootApplication
 @EnableSwagger2
 @EnableConfigurationProperties({MarketConfig.class})
 public class MarketApplication implements CommandLineRunner {

    private final MarketService service;
    private final MarketConfig config;

    public MarketApplication(MarketService service, MarketConfig config) {
       this.service = service;
       this.config = config;
    }