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 set up the someNumber variable differently 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?

mrkernelpanic · Accepted Answer · 2018-12-17 12:29:37Z

7

Well what you can do is the following:

Create a new class: MyEnumProperties

@ConfigurationProperties(prefix = "enumProperties")
@Getter
public class MyEnumProperties {

    private Map<String, Long> enumMapping;

}

Enable ConfigurationProperties to your SpringBootApplication/ any Spring Config via
```
@EnableConfigurationProperties(value = MyEnumProperties.class)
```

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

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

In your application code autowire your properties like this:
```
@Autowired
private MyEnumProperties properties;
```

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

answered Dec 17, 2018 at 12:29

mrkernelpanic

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Comments

danielh · Accepted Answer · 2018-12-17 12:51:48Z

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();

Thank you very much for this solution, it is exactly what I needed.

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