AggregationOptions options = new AggregationOptions.Builder().allowDiskUse(true).build();Aggregation agg = Aggregation.newAggregation().withOptions(options);

Aggregation agg = Aggregation.newAggregation(Aggregation.group(field1, field2, field3).sum(field4).as("sampleField1").sum(field5).as("sampleField2"),Aggregation.project(field4, field5),new AggregationOperation() { @Overridepublic DBObject toDBObject(AggregationOperationContext context) {return new BasicDBObject("$out", "test");}}).withOptions(options);

mongo.aggregate(agg, sourceCollection, Test.class);

红色部分是重点,构造这个agg可以将得到的结果导入插入到out中，并且不会有16M的限制问题。

Aggregation agg = Aggregation.newAggregation(Aggregation.group(, OnofflineUserHistoryField.MAC, StalogField.UTC_CODE).sum(OnofflineUserHistoryField.WIFI_UP_DOWN).as(OnofflineUserHistoryField.WIFI_UP_DOWN).sum(OnofflineUserHistoryField.ACTIVE_TIME).as(OnofflineUserHistoryField.ACTIVE_TIME),Aggregation.project("mac","buildingId","utcCode",OnofflineUserHistoryField.ACTIVE_TIME, OnofflineUserHistoryField.WIFI_UP_DOWN).and(new AggregationExpression() {@Overridepublic DBObject toDbObject(AggregationOperationContext context) {return new BasicDBObject("$cond", new Object[]{new BasicDBObject("$eq", new Object[]{ "$tenantId", 0}),20161114,20161114});}}).as("day").andExclude("_id"),　　　　　　　　　　　　或者

and(new AggregationExpression() {

　　　　　　　　　　　　　@Override

　　　　　　　　　　　　　public DBObject toDbObject(AggregationOperationContext context) {

　　　　　　　　　　　　　　　　return new BasicDBObject("$add", new Object[] { 20141114 });

　　　　　　　　　　　　}  

　　　　　　　　　　　　　}).as("day").andExclude("_id"),

　　　　　　　　　　　　new AggregationOperation() { @Overridepublic DBObject toDBObject(AggregationOperationContext context) {return new BasicDBObject("$out", "dayStaInfoTmp");}}).withOptions(options);红色和棕色部分为聚合中增加常量的两种方法。目前没有找到更方便的聚合添加常量的方法。