com.netflix.config

Class DynamicContextualProperty<T>

java.lang.Object

com.netflix.config.PropertyWrapper<T>

com.netflix.config.DynamicContextualProperty<T>

Type Parameters:

T - Data type of the property, e.g., Integer, Boolean

All Implemented Interfaces:

Property<T>

public class DynamicContextualProperty<T>
extends PropertyWrapper<T>

A property that has multiple possible values associated with it and determines the value according to the runtime context, which can include deployment context, values of other properties or attributes of user input.

The value is defined as a JSON blob that consists of multiple conditions and value associated with each condition. The following is an example:

[
    {
       "if":  
              {"@environment":["prod"],
               "@region":["us-east-1"]
              },
       "value":5
    },
     {
        "if":
             {"@environment":["test", "dev"]},
        "value":10
     },
    {
        "value":2
    }
]
 

This blob means that

If "@enviornment" is "prod" and "@region" is "us-east-1", value of the property is integer 5; (Note: if you use ConfigurationManager, "@enviornment" and "@region" are automatically exported as properties from DeploymentContext) Else if "@environment" is either "test" or "dev", the value is 10; Otherwise, the default value of the property is 2

In order to make this work, a Predicate is needed to determine if the current runtime context matches any of the conditions described in the JSON blob. The predicate can be passed in as a parameter of the constructor, otherwise the default one will interpret each key in the "dimensions" as a key of a DynamicProperty, and the list of values are the acceptable values of the DynamicProperty.

For example:

String json = ... // string as the above JSON blob
      ConfigurationManager.getConfigInstance().setProperty("@environment", "test"); // no need to do this in real application as property is automatically set 
        ConfigurationManager.getConfigInstance().setProperty("contextualProp", json);
        DynamicContextualProperty<Integer> prop = new DynamicContextualProperty<Integer>("contextualProp", 0);
        prop.get(); // returns 10 as "@environment" == "test" matches the second condition