predicate filter action Predicate Filter Action

Provided by: "Apache Software Foundation"

Support Level for this Kamelet is: "Preview"

Filter based on a JsonPath Expression

Configuration Options

The following table summarizes the configuration options available for the predicate-filter-action Kamelet:

Property Name Description Type Default Example

expression *

Expression

The JsonPath Expression to evaluate, without the external parenthesis. Since this is a filter, the expression will be a negation, this means that if the foo field of the example is equals to John, the message will go ahead, otherwise it will be filtered out.

string

"@.foo =~ /.*John/"
Fields marked with (*) are mandatory.

Usage

This section summarizes how the predicate-filter-action can be used in various contexts.

Knative Action

The predicate-filter-action Kamelet can be used as intermediate step in a Knative binding.

predicate-filter-action-binding.yaml
apiVersion: camel.apache.org/v1alpha1
kind: KameletBinding
metadata:
  name: predicate-filter-action-binding
spec:
  source:
    ref:
      kind: Kamelet
      apiVersion: camel.apache.org/v1alpha1
      name: timer-source
    properties:
      message: "Hello"
  steps:
  - ref:
      kind: Kamelet
      apiVersion: camel.apache.org/v1alpha1
      name: predicate-filter-action
    properties:
      expression: "@.foo =~ /.*John/"
  sink:
    ref:
      kind: Channel
      apiVersion: messaging.knative.dev/v1
      name: mychannel

Make sure you have Camel K installed into the Kubernetes cluster you’re connected to.

Save the predicate-filter-action-binding.yaml file into your hard drive, then configure it according to your needs.

You can run the action using the following command:

kubectl apply -f predicate-filter-action-binding.yaml

Dependencies

The Kamelet needs the following dependencies:

  • camel:core

  • camel:kamelet

  • camel:jsonpath

Binding to Knative using the Kamel CLI:

The procedure described above can be simplified into a single execution of the kamel bind command:

kamel bind timer-source?message=Hello --step predicate-filter-action -p "step-0.expression=@.foo =~ /.*John/" channel:mychannel

This will create the KameletBinding under the hood and apply it to the current namespace in the cluster.

Kafka Action

The predicate-filter-action Kamelet can be used as intermediate step in a Kafka binding.

predicate-filter-action-binding.yaml
apiVersion: camel.apache.org/v1alpha1
kind: KameletBinding
metadata:
  name: predicate-filter-action-binding
spec:
  source:
    ref:
      kind: Kamelet
      apiVersion: camel.apache.org/v1alpha1
      name: timer-source
    properties:
      message: "Hello"
  steps:
  - ref:
      kind: Kamelet
      apiVersion: camel.apache.org/v1alpha1
      name: predicate-filter-action
    properties:
      expression: "@.foo =~ /.*John/"
  sink:
    ref:
      kind: KafkaTopic
      apiVersion: kafka.strimzi.io/v1beta1
      name: my-topic

Ensure that you’ve installed Strimzi and created a topic named my-topic in the current namespace. Make also sure you have Camel K installed into the Kubernetes cluster you’re connected to.

Save the predicate-filter-action-binding.yaml file into your hard drive, then configure it according to your needs.

You can run the action using the following command:

kubectl apply -f predicate-filter-action-binding.yaml

Binding to Kafka using the Kamel CLI:

The procedure described above can be simplified into a single execution of the kamel bind command:

kamel bind timer-source?message=Hello --step predicate-filter-action -p "step-0.expression=@.foo =~ /.*John/" kafka.strimzi.io/v1beta1:KafkaTopic:my-topic

This will create the KameletBinding under the hood and apply it to the current namespace in the cluster.

Kamelet source file

Have a look at the following link:

https://github.com/apache/camel-kamelets/blob/main/predicate-filter-action.kamelet.yaml

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