Configuring an enum in Spring using application.properties

Question

I have the following enum:

public enum MyEnum {
    NAME("Name", "Good", 100),
    FAME("Fame", "Bad", 200);

    private String lowerCase;
    private String atitude;
    private long someNumber;

    MyEnum(String lowerCase, String atitude, long someNumber) {
        this.lowerCase = lowerCase;
        this.atitude = atitude;
        this.someNumber = someNumber;
    }
}

I want to setup the someNumber variable different for both instances of the enum using application.properties file. Is this possible and if not, should i split it into two classes using an abstract class/interface for the abstraction?

Answer 1

You can't/shouldn't change values of a enum in Java. Try using a class instead:

public class MyCustomProperty { 
    // can't change this in application.properties
    private final String lowerCase;
    // can change this in application.properties
    private String atitude;
    private long someNumber;

    public MyCustomProperty (String lowerCase, String atitude, long someNumber) {
        this.lowerCase = lowerCase;
        this.atitude = atitude;
        this.someNumber = someNumber;
    }
    // getter and Setters
}

Than create a custom ConfigurationProperties:

@ConfigurationProperties(prefix="my.config")
public class MyConfigConfigurationProperties {
    MyCustomProperty name = new MyCustomProperty("name", "good", 100);
    MyCustomProperty fame = new MyCustomProperty("fame", "good", 100);

    // getter and Setters

    // You can also embed the class MyCustomProperty here as a static class. 
    // For details/example look at the linked SpringBoot Documentation
}

Now you can change the values of my.config.name.someNumber and my.config.fame.someNumber in the application.properties file. If you want to disallow the change of lowercase/atitude make them final.

Before you can use it you have to annotate a @Configuration class with @EnableConfigurationProperties(MyConfigConfigurationProperties.class). Also add the org.springframework.boot:spring-boot-configuration-processor as an optional dependency for a better IDE Support.

If you want to access the values:

@Autowired
MyConfigConfigurationProperties config;
...
config.getName().getSumeNumber();

Answer 2

Well what you can do is the following:

1. Create a new class: MyEnumProperties

   @ConfigurationProperties(prefix = "enumProperties")
   @Getter
   public class MyEnumProperties {
   
       private Map<String, Long> enumMapping;
   
   }
   

2. Enable ConfigurationProperties to your SpringBootApplication/ any Spring Config via

   @EnableConfigurationProperties(value = MyEnumProperties.class)
   

3. Now add your numbers in application.properties file like this:

   enumProperties.enumMapping.NAME=123
   enumProperties.enumMapping.FAME=456
   

4. In your application code autowire your properties like this:

   @Autowired
   private MyEnumProperties properties;
   

5. Now here is one way to fetch the ids:

   properties.getEnumMapping().get(MyEnum.NAME.name()); //should return 123
   

You can fetch this way for each Enum value the values defined in your application.properties