ReferenceError：db未定义＆＃34;

Question

我正在尝试使用以下代码从Java运行一些Js代码：

public void mapReduceScript()
    {
        try{
        MongoClient mongoClient = new MongoClient( CoreConfigModel.get("com.dice.api.mongo.host") , Integer.parseInt(CoreConfigModel.get("com.dice.api.mongo.port")));
        // Now connect to your databases
        DB db = mongoClient.getDB( "tracking" );
         System.out.println("Connect to database successfully");
        boolean auth = db.authenticate(CoreConfigModel.get("mongo.username"), CoreConfigModel.get("mongo.password").toCharArray() );
         System.out.println("Authentication: "+auth);
         ClassLoader classLoader = Thread.currentThread()
                    .getContextClassLoader();
         InputStream reduceStream = classLoader.getResourceAsStream("/data/mapReduceFunctionsByGroupIdIterative.js");
         String reduce = IOUtils.toString(reduceStream, "UTF-8");
         db.eval(reduce, new BasicDBObject("nolock", true));
        }
        catch (Exception e)
        {
            System.out.println(e);
        }

    }

以下是mapReduceFunctionsByGroupIdIterative.js

的内容

 function mapFunction() {
    if (!this.eventdata.Viewed || this.eventdata.Viewed.length === 0) {
        return;
    }
    var key = this.groupid;
    var value = {
        Dockey: this.eventdata.Viewed[0].Dockey,
        PID: this.eventdata.Viewed[0].PID,
        datecreated: this.datecreated,
    entityid: this.entityid
    };
    emit(key, value);
}

function reduceFunction(key, values) {
    function merge(target, firstSource) { 'use strict';
        if (target === undefined || target === null)
            throw new TypeError('Cannot convert first argument to object');

        var to = Object(target);

        var hasPendingException = false;
        var pendingException;

        for (var i = 1; i < arguments.length; i++) {
            var nextSource = arguments[i];
            if (nextSource === undefined || nextSource === null)
                continue;

            var keysArray = Object.keys(Object(nextSource));
            for (var nextIndex = 0, len = keysArray.length; nextIndex < len; nextIndex++) {
                var nextKey = keysArray[nextIndex];
                try {
                    var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey);
                    if (desc !== undefined && desc.enumerable)
                        to[nextKey] = nextSource[nextKey];
                } catch (e) {
                    if (!hasPendingException) {
                        hasPendingException = true;
                    pendingException = e;
                }
            }
        }

        if (hasPendingException)
            throw pendingException;
        }
        return to;
    }

    var mostRecentViews = {
        Dockey: {},
        PID: {}
    };

    values.forEach(function (value) {
        var key = value.Dockey ? 'Dockey' : 'PID';
        var reducedValue = {
            profileid: value[key],
            datecreated: value.datecreated,
        entityid: value.entityid
        };
        if (!(value[key] in this[key]) ||
                new Date(value.datecreated) > new Date(this[key][value[key]].datecreated)) {
            this[key][value[key]] = reducedValue;
        }
    }, mostRecentViews);

    var reducedObject = merge({}, mostRecentViews.Dockey, mostRecentViews.PID);

    return reducedObject;
}

function finalizeFunction(key, reducedValue) {
    var finalizedObject = Object.keys(reducedValue).map(function (key, index, array) {
        return reducedValue[key];
    });

    return finalizedObject;
}

var lastrundate = db.TRACKING_DATA.findOne({'_id': 'lastruntimeGroup'}).lastruntime;

db.TRACKING_DATA.mapReduce(mapFunction,
                            reduceFunction,
                            {
                            out: { reduce: "LASTVIEWED_GROUP"},
                            query: { datecreated: 
                                            { $gt: lastrundate }
                                        },
                            finalize: finalizeFunction
                            }
                        )       

db.TRACKING_DATA.update({'_id': 'lastruntimeGroup'},{'_id': 'lastruntimeGroup', 'lastruntime': new Date()},{upsert:true})

然而，当我执行代码时，我会抛出错误：

com.mongodb.CommandFailureException: { "serverUsed" : "127.0.0.1:27017" , "errmsg" : "exception: ReferenceError: db is not defined" , "code" : 16722 , "ok" : 0.0}

我在我的Java代码中有两个对db one的引用：

DB db = mongoClient.getDB( "tracking" );

我的Js代码中的一个应该通过以下方式在mongo shell中运行：

db.eval(reduce, new BasicDBObject("nolock", true));

我在shell上运行了js文件，它按预期工作，所以我的java代码或调用db.eval()的东西都在做一些时髦的事情。