76 lines
2.9 KiB
Markdown
76 lines
2.9 KiB
Markdown
Barrier Sample
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==============
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This example demonstrates the use of a process barrier component to suspend a thread until some asynchronous operation
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completes. The first example uses an **HTTP Inbound Gateway**, splits the request, sends the splits to rabbitmq and then
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waits for
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the publisher confirms. Finally, the results are returned to the caller.
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The sample is a Spring Boot application that loads 2 contexts:
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* Client - Sends **A,B,C** to the server
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* Server - Web application
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The server context has 3 integration flows:
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```
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http -> splitter -> amqp
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|-> barrier
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amqp(Acks) -> aggregator -> barrier (release)
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qmqp(inbound) -> nullChannel
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```
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The last flow drains the messages and allows the auto-delete queue to be removed when the application is closed.
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## Running the sample
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$ gradlew :barrier:run
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This will package the application and run it using the [Gradle Application Plugin](http://www.gradle.org/docs/current/userguide/application_plugin.html)
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#### Using an IDE such as SpringSource Tool Suite™ (STS)
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In STS (Eclipse), go to package **org.springframework.integration.samples.barrier**, right-click **Application** and select **Run as** --> **Java Application** (or Spring Boot Application).
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### Output
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The gateway (**client**) initiates a simple request posting "A,B,C" to the **server** and the **server** responds with the results.
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You should see the following output from the server:
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++++++++++++ Replied with: Result: A: ack=true, B: ack=true, C: ack=true ++++++++++++
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### Error Handling
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The second example uses a simple gateway to launch some asynchronous tasks and waits for those tasks to complete.
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It shows how you might return an exception to the caller if one or more of those tasks fail.
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An aggregator is used to aggregate the results; if there are no errors, the results are returned; if one or more
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errors occurred, an exception is sent to release the barrier; this is thrown to the caller and has all the consolidated
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results in a property.
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You can run this example from an IDE, such as STS using the technique above; in this case, the class is
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**ErrorHandlingApplication** in the **org.springframework.integration.samples.barrier** package.
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It sends a list of integers to the flow:
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[2, 0, 2, 0, 2]
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The zeros should fail and in stderr you should see the results:
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ConsolidatedResultsException
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[results=
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[5
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org.springframework.integration.transformer.MessageTransformationException:
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Failed to transform Message; nested exception is org.springframework.messaging.MessageHandlingException:
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Expression evaluation failed: 10 / payload; nested exception is java.lang.ArithmeticException: / by zero
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5
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org.springframework.integration.transformer.MessageTransformationException:
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Failed to transform Message; nested exception is org.springframework.messaging.MessageHandlingException:
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Expression evaluation failed: 10 / payload; nested exception is java.lang.ArithmeticException: / by zero
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5]
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]
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