org.apache.nifi.expression.AttributeExpression Maven / Gradle / Ivy
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* 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.expression;
import org.apache.nifi.flowfile.FlowFile;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.registry.VariableRegistry;
/**
* Defines a type of expression language statement that can be applied
* parametrized by various attributes and properties as specified in each of
* the method calls. AttributeExpression evaluations may be also backed by a
* {@link VariableRegistry} used to substitute attributes and variables found in
* the expression for which the registry has a value.
*/
public interface AttributeExpression {
/**
* @return Evaluates the expression without any additional attributes.
* @throws ProcessException if unable to evaluate
*/
String evaluate() throws ProcessException;
/**
* Evaluates the expression without additional attributes but enables the
* expression result to be decorated before returning.
*
* @param decorator to execute on the resulting expression value
* @return evaluated value
* @throws ProcessException if failure in evaluation
*/
String evaluate(AttributeValueDecorator decorator) throws ProcessException;
/**
* Evaluates the expression providing access to additional variables
* including the flow file properties such as file size, identifier, etc..
* and also all of the flow file attributes.
*
* @param flowFile to evaluate
* @return evaluated value
* @throws ProcessException if failure evaluating
*/
String evaluate(FlowFile flowFile) throws ProcessException;
/**
* Evaluates the expression providing access to additional variables
* including the flow file properties such as file size, identifier, etc..
* and also all of the flow file attributes. The resulting value after
* executing any variable substitution and expression evaluation is run
* through the given decorator and returned.
*
* @param flowFile to evaluate
* @param decorator for evaluation
* @return evaluated value
* @throws ProcessException if failed to evaluate
*/
String evaluate(FlowFile flowFile, AttributeValueDecorator decorator) throws ProcessException;
/**
* @return the type that is returned by the Expression
*/
ResultType getResultType();
enum ResultType {
STRING, BOOLEAN, WHOLE_NUMBER, DATE, INSTANT, DECIMAL, NUMBER;
}
}