Adding Functionality to Apache NiFi
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Documenting FlowFile Attribute Interaction

Many times a processor will expect certain FlowFile attributes be set on in-bound FlowFiles in order for the processor to function properly. In other cases a processor may update or create FlowFile attributes on the out-bound FlowFile. Processor developers may document both of these behaviors using the ReadsAttribute and WritesAttribute documentation annotations. These attributes are used to generate documentation that gives users a better understanding of how a processor will interact with the flow.

Note: Because Java 7 does not support repeated annotations on a type, you may need to use ReadsAttributes and WritesAttributes to indicate that a processor reads or writes multiple FlowFile attributes. This annotation can only be applied to Processors. An example is listed below:

         @WritesAttributes({ @WritesAttribute(attribute = "invokehttp.status.code", description = "The status code that is returned"),
        @WritesAttribute(attribute = "invokehttp.status.message", description = "The status message that is returned"),
        @WritesAttribute(attribute = "invokehttp.response.body", description = "The response body"),
        @WritesAttribute(attribute = "invokehttp.request.url", description = "The request URL"),
        @WritesAttribute(attribute = "", description = "The transaction ID that is returned after reading the response"),
        @WritesAttribute(attribute = "invokehttp.remote.dn", description = "The DN of the remote server") })
public final class InvokeHTTP extends AbstractProcessor {