com.amazonaws.services.dynamodbv2.xspec.IfNotExistsFunction Maven / Gradle / Ivy

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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2015-2016 Amazon Technologies, 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://aws.amazon.com/apache2.0
 *
 * This file 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.amazonaws.services.dynamodbv2.xspec;

import com.amazonaws.annotation.Beta;

/**
 * Represents an if_not_exists(path, operand) function in building expressions. If the
 * item does not contain an attribute at the specified path, then if_not_exists
 * evaluates to operand; otherwise, it evaluates to path. You can use this
 * function to avoid overwriting an attribute already present in the item.
 * 
 * This object is as immutable (or unmodifiable) as the underlying operand given
 * during construction.
 */
@Beta
public final class IfNotExistsFunction extends FunctionOperand {
    private final PathOperand attr;
    private final Operand operand;

    IfNotExistsFunction(PathOperand attr, Operand operand) {
        this.attr = attr;
        this.operand = operand;
    }

    @Override
    String asSubstituted(SubstitutionContext context) {
        return "if_not_exists(" + attr.asSubstituted(context) + ","
                + operand.asSubstituted(context) + ")";
    }
}