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The AWS Java SDK for Amazon DynamoDB module holds the client classes that are used for communicating with Amazon DynamoDB Service
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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 java.util.Map;

import org.apache.http.annotation.Immutable;

import com.amazonaws.annotation.Beta;

/**
 * A path operand that refers to a map attribute in DynamoDB; used for building expressions.
 * 
 * Use {@link ExpressionSpecBuilder#M(String)} to instantiate this class.
 */
@Beta
@Immutable
public final class M extends PathOperand {

    M(String attrName) {
        super(attrName);
    }

    public ComparatorCondition eq(FunctionOperand value) {
        return new ComparatorCondition("=", this, value);
    }

    public ComparatorCondition eq(M that) {
        return new ComparatorCondition("=", this, that);
    }

    public ComparatorCondition ne(FunctionOperand value) {
        return new ComparatorCondition("<>", this, value);
    }

    public ComparatorCondition ne(M that) {
        return new ComparatorCondition("<>", this, that);
    }

    public IfNotExistsFunction ifNotExists(M defaultValue) {
        return new IfNotExistsFunction(this, defaultValue);
    }

    /**
     * Returns a SetAction object used for building update
     * expression. If the attribute referred to by this path operand doesn't
     * exist, the returned object represents adding the attribute value of the
     * specified source path operand to an item. If the current attribute
     * already exists, the returned object represents the value replacement of
     * the current attribute by the attribute value of the specified source path
     * operand.
     */
    public SetAction set(M source) {
        return new SetAction(this, source);
    }

    /**
     * Returns a SetAction object used for building update
     * expression. If the attribute referred to by this path operand doesn't
     * exist, the returned object represents adding the specified value as an
     * attribute to an item. If the attribute referred to by this path operand
     * already exists, the returned object represents the value replacement of
     * the current attribute by the specified value.
     */
    public SetAction set(Map value) {
        return new SetAction(this, new LiteralOperand(value));
    }

    /**
     * Returns a SetAction object used for building update
     * expression. If the attribute referred to by this path operand doesn't
     * exist, the returned object represents adding the value of evaluating the
     * specified IfNotExists function as an attribute to an item.
     * If the attribute referred to by this path operand already exists, the
     * returned object represents the value replacement of the current attribute
     * by the value of evaluating the specified IfNotExists
     * function.
     */
    public SetAction set(IfNotExistsFunction ifNotExistsFunction) {
        return new SetAction(this, ifNotExistsFunction);
    }

    /**
     * Returns a comparator condition (that evaluates to true if the attribute value
     * referred to by this path operand is equal to the specified value) for
     * building condition expression.
     */
    public ComparatorCondition eq(Map value) {
        return new ComparatorCondition("=", this, new LiteralOperand(value));
    }

    /**
     * Returns a comparator condition (that evaluates to true if the attribute value
     * referred to by this path operand is not equal to that of the specified
     * path operand) for building condition expression.
     */
    public ComparatorCondition ne(Map value) {
        return new ComparatorCondition("<>", this, new LiteralOperand(value));
    }

    /**
     * Returns an IfNotExists object which represents an if_not_exists(path, operand) function call where path refers to that
     * of the current path operand; used for building expressions.
     * 
     * 
     * "if_not_exists (path, operand) – 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."
     * 
     * 
     * @param defaultValue
     *            the default value that will be used as the operand to the
     *            if_not_exists function call.
     */
    public IfNotExistsFunction ifNotExists(Map defaultValue) {
        return new IfNotExistsFunction(this, new LiteralOperand(defaultValue));
    }
}