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Chapter 42. Predicate Filter Action

Filter based on a JsonPath Expression

42.1. Configuration Options
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The following table summarizes the configuration options available for the predicate-filter-action Kamelet:

Expand
PropertyNameDescriptionTypeDefaultExample

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/"

Note

Fields marked with an asterisk (*) are mandatory.

42.2. Dependencies
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At runtime, the predicate-filter-action Kamelet relies upon the presence of the following dependencies:

  • camel:core
  • camel:kamelet
  • camel:jsonpath

42.3. Usage
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This section describes how you can use the predicate-filter-action.

42.3.1. Knative Action
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You can use the predicate-filter-action Kamelet as an 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
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42.3.1.1. Prerequisite
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Make sure you have "Red Hat Integration - Camel K" installed into the OpenShift cluster you’re connected to.

42.3.1.2. Procedure for using the cluster CLI
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  1. Save the predicate-filter-action-binding.yaml file to your local drive, and then edit it as needed for your configuration.

  2. Run the action by using the following command: 

    oc apply -f predicate-filter-action-binding.yaml
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42.3.1.3. Procedure for using the Kamel CLI
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Configure and run the action by using the following command: 

kamel bind timer-source?message=Hello --step predicate-filter-action -p "step-0.expression=@.foo =~ /.*John/" channel:mychannel
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This command creates the KameletBinding in the current namespace on the cluster.

42.3.2. Kafka Action
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You can use the predicate-filter-action Kamelet as an 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
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42.3.2.1. Prerequisites
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Ensure that you’ve installed the AMQ Streams operator in your OpenShift cluster and created a topic named my-topic in the current namespace. Make also sure you have "Red Hat Integration - Camel K" installed into the OpenShift cluster you’re connected to.

42.3.2.2. Procedure for using the cluster CLI
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  1. Save the predicate-filter-action-binding.yaml file to your local drive, and then edit it as needed for your configuration.

  2. Run the action by using the following command: 

    oc apply -f predicate-filter-action-binding.yaml
    Copy to Clipboard Toggle word wrap

42.3.2.3. Procedure for using the Kamel CLI
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Configure and run the action by using the following command: 

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

This command creates the KameletBinding in the current namespace on the cluster.

42.4. Kamelet source file
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https://github.com/openshift-integration/kamelet-catalog/blob/kamelet-catalog-1.6/predicate-filter-action.kamelet.yaml

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