com.streamsets.pipeline.api.el.ELVars Maven / Gradle / Ivy
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/*
* Copyright 2017 StreamSets Inc.
*
* Licensed 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 com.streamsets.pipeline.api.el;
/**
* The ELVars hold all constants, variables and context variables available during an EL evaluation.
*
*
* @see ELEval
* @see ELEval#getVariablesInScope()
*/
public interface ELVars {
/**
* Returns the specified EL constant.
*
* The EL constant has been defined in one of the classes indicated in the
* {@link com.streamsets.pipeline.api.ConfigDef#elDefs()} attribute, or in a class annotated with
* {@link com.streamsets.pipeline.api.ElDef} and available to the stage library.
*
* @param name the EL constant name.
* @return the specified EL constant, or NULL if not defined.
*/
public Object getConstant(String name);
/**
* Adds a variable to be available in the EL being evaluated.
*
* @param name variable name.
* @param value variable value.
*/
public void addVariable(String name, Object value);
/**
* Adds a context variable to be available within the evaluation of an EL, but not in the EL itself.
*
* Method associated with an EL function have access to the context variables via the
* {@link ELEval#getVariablesInScope()} method.
*
* @param name context variable name.
* @param value context variable value.
*/
public void addContextVariable(String name, Object value);
/**
* Indicates if a variable is defined or not.
* @param name variable name.
* @return if the variable is defined or not.
*/
public boolean hasVariable(String name);
/**
* Returns the variable value.
* @param name variable name.
* @return the variable value.
*/
public Object getVariable(String name);
/**
* Indicates if a context variable is defined or not.
* @param name variable name.
* @return if the context variable is defined or not.
*/
public boolean hasContextVariable(String name);
/**
* Returns the context variable value.
* @param name context variable name.
* @return the context variable value.
*/
public Object getContextVariable(String name);
}