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 
 

Nested Class Summary

static class

DynamicContextualProperty.Value<T>

Field Summary

Fields inherited from class com.netflix.config.PropertyWrapper

defaultValue, prop

Constructor Summary

DynamicContextualProperty(java.lang.String propName, T defaultValue)

DynamicContextualProperty(java.lang.String propName, T defaultValue, com.google.common.base.Predicate<java.util.Map<java.lang.String,java.util.Collection<java.lang.String>>> predicate)

Method Summary

T	getValue() Get current typed value of the property.
protected void	propertyChanged() Called when the property value is updated.

Methods inherited from class com.netflix.config.PropertyWrapper

addCallback, addValidator, getChangedTimestamp, getDefaultValue, getDynamicProperty, getName, propertyChanged, registerSubClassWithNoCallback, removeAllCallbacks, toString, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

DynamicContextualProperty

public DynamicContextualProperty(java.lang.String propName,
                                 T defaultValue,
                                 com.google.common.base.Predicate<java.util.Map<java.lang.String,java.util.Collection<java.lang.String>>> predicate)

DynamicContextualProperty

public DynamicContextualProperty(java.lang.String propName,
                                 T defaultValue)

Method Detail

propertyChanged

protected final void propertyChanged()

Description copied from class: PropertyWrapper

Called when the property value is updated. The default does nothing. Subclasses are free to override this if desired.

Overrides:

propertyChanged in class PropertyWrapper<T>

getValue

public T getValue()

Description copied from class: PropertyWrapper

Get current typed value of the property.

Specified by:

getValue in interface Property<T>

Specified by:

getValue in class PropertyWrapper<T>

Returns:

the latest property value