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| <title>SpringContextProcessor</title> |
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| <!-- Processor Documentation ================================================== --> |
| <h2>Description:</h2> |
| <p> |
| <b>SpringContextProcessor</b> – allows integration of processes encapsulated in Spring Application Context to run as NiFi |
| processor by becoming a runtime host for an instance of Spring Application Context. |
| </p> |
| <p> |
| Communication between NiFi and process encapsulated within Spring Application Context is accomplished via Spring Messaging |
| (one of the core modules of Spring Framework) and supports 3 usage modes: |
| <ul> |
| <li><i>Headless</i> - no interaction with NiFi, meaning nothing is sent to it and nothing is received from it (i.e., some monitoring app). |
| In this case NiFi simply plays the role of the runtime host.</li> |
| <li><i>One way (NiFi -> Spring or Spring -> NiFi). </i> - This depends on existence of pre-defined message channel in Spring |
| Application Context. The name of the channel should be “fromNiFi” and the type <i>org.springframework.messaging.MessageChannel.</i></li> |
| <li><i>By-directional (NiFi -> Spring -> NiFi or Spring -> NiFi -> Spring)</i> - This depends on existence of two channels |
| in Spring Application Context. One channel receives messages from NiFi with name “fromNiFi” and type <i>org.springframework.messaging.MessageChannel</i>i> |
| and another is to receive messages from Spring with name “toNiFi” and type <i>org.springframework.messaging.PollableChannel.</i></li> |
| </ul> |
| The example below demonstrates template configuration for bi-directional Spring Application Context configuration: |
| <code> |
| <pre> |
| <int:channel id=”fromNiFi”/> |
| |
| <!— |
| your custom app configuration to receive messages from ‘fromNiFi’ channel and optionally send back to NiFi via ‘toNiFi’ channel. |
| It could contain any Spring-based application (i.e., Spring Integration, Apache Camel and/or custom code). All you need to do is inject |
| channels into your beans and send/receive messages from it. |
| --> |
| |
| <int:channel id="toNiFi"> |
| <int:queue/> |
| </int:channel> |
| </pre> |
| </code> |
| </p> |
| <p> |
| The component is based on assumption that user has an existing Spring Application encapsulated in Spring Context that exposes optional in/out |
| MessagingChannels to allow data to flow to/from ApplicationContext and into/out-of. NiFi. |
| Such application is realized by having a directory on the file system, which contains contains all required resources for such application to run. |
| Such resources usually are JAR files to satisfy application's class-path as well as JAR representing the application and its configuration. |
| Below is the example of what such directory may contain. In this case the 'SI_DEMO-0.0.1-SNAPSHOT.jar' represents the actual application and the rest |
| of the JARs represent class-path dependency required by an application. |
| <pre> |
| deps |
| ├── SI_DEMO-0.0.1-SNAPSHOT.jar |
| ├── aopalliance-1.0.jar |
| ├── commons-logging-1.2.jar |
| ├── spring-aop-VERSION.jar |
| ├── spring-beans-VERSION.jar |
| ├── spring-context-VERSION.jar |
| ├── spring-core-VERSION.jar |
| ├── spring-expression-VERSION.jar |
| ├── spring-integration-core-VERSION.jar |
| ├── spring-messaging-VERSION.jar |
| </pre> |
| </p> |
| <p> |
| You introduce the processor the usual way and then configure its properties: |
| <ul> |
| <li><i><b>Application Context config path</b></i> [REQUIRED] - a path to the Application Context configuration. |
| The path is relative to the class-path of the application defined by the <i>Application Context class path</i> property </li> |
| <li><i><b>Application Context class path</b></i> [REQUIRED] - a path to a directory on the file system where application dependencies are. </li> |
| <li><i>Send Timeout</i> [OPTIONAL] - the wait time for sending messages to Spring Application Context. Only required if NiFi plans to send data to Spring. |
| Defaults to 0 (don't wait). FlowFiles that were successfully sent to Spring will be removed from session while FlowFiles that could not be sent to |
| Spring will be routed to <i>failure</i> relationship.</li> |
| <li><i>Receive Timeout</i> - [OPTIONAL] - the wait time for receiving messages from Spring Application Context. Only required if NiFi plans to receive data from Spring. |
| Defaults to 0 (don't wait). FlowFile is created if and only if a message is successfully received from Spring. It is then transferred to <i>success</i> relationship.</li> |
| </ul> |
| </p> |
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