Expression Languages

An expression language is a way to define conditions or manipulate messages declaratively. They are used to evaluate and manipulate data within a message, allowing for the creation of more complex and flexible routes.

See how to add an expression language directly through the form of an EIP in the Diagram tab:

language expression

Here are the expression languages supported by Sensedia Integrations:

The examples show the use of the languages in the Choice component, but they can be used in any context that supports languages.

Constant: returns a constant value.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  constant:
                    expression: 'sensedia'
                steps:
                - log:
                    message: 'When activated'

ExchangeProperty: accesses Exchange properties.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  exchangeProperty:
                    expression: 'myproperty'
                steps:
                - log:
                    message: 'When activated'

Groovy: uses Groovy scripts to manipulate messages.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  groovy:
                    expression: 'Math.random() > 0.5'
                steps:
                - log:
                    message: 'When activated'

Header: accesses values from message headers.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  header:
                    expression: 'myheader'
                steps:
                - log:
                    message: 'When activated'

JQ: uses the JQ language to query and manipulate JSON.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  jq:
                    expression: '.store.book.price < 30'
                steps:
                - log:
                    message: 'When activated'

JSONPath: similar to XPath, but for JSON.

     - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  jsonpath:
                    expression: $.model.Details[?(@['Random nonsense'] == 'New today')]
                steps:
                - log:
                    message: 'When activated'

OGNL: uses Object-Graph Navigation Language expressions to access data.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  ognl:
                    expression: 'request.headers.foo == "bar"'
                steps:
                - log:
                    message: 'When activated'

Simple: a simple language for expressions and manipulations.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  simple:
                    expression: ${header.id} == 2
                steps:
                - log:
                    message: 'When activated'

XPath: used to query and manipulate XML.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  xpath:
                    expression: '/person/@id > 30'
                steps:
                - log:
                    message: 'When activated'

XQuery: uses XQuery to query and manipulate XML.

      - from:
          uri: rest:post:/demo
          parameters: {}
          steps:
          - choice:
              otherwise:
                steps:
                - log:
                    message: 'Otherwise activated'
              when:
              - expression:
                  xquery:
                    expression: '//foo/id > 30'
                steps:
                - log:
                    message: 'When activated'

For more details, access Apache Camel official documentation.

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