org.apache.nifi.annotation.behavior.InputRequirement Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.annotation.behavior;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
*
* Marker interface that a Processor can use to indicate whether it accepts, requires, or forbids
* input from other Processors. This information is used by the framework in order to ensure that
* a Processor is marked as invalid if it is missing necessary input or has input that will be ignored.
* This information also is used by the NiFi UI in order to prevent users from making connections
* to Processors that don't make sense.
*
*/
@Documented
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface InputRequirement {
Requirement value();
enum Requirement {
/**
* This value is used to indicate that the Processor requires input from other Processors
* in order to run. As a result, the Processor will not be valid if it does not have any
* incoming connections.
*/
INPUT_REQUIRED,
/**
* This value is used to indicate that the Processor will consume data from an incoming
* connection but does not require an incoming connection in order to perform its task.
* If the {@link InputRequirement} annotation is not present, this is the default value
* that is used.
*/
INPUT_ALLOWED,
/**
* This value is used to indicate that the Processor is a "Source Processor" and does
* not accept incoming connections. Because the Processor does not pull FlowFiles from
* an incoming connection, it can be very confusing for users who create incoming connections
* to the Processor. As a result, this value can be used in order to clarify that incoming
* connections will not be used. This prevents the user from even creating such a connection.
*/
INPUT_FORBIDDEN;
}
}