java mongodb聚合统计查询，比较两个字段

DBObject group = (DBObject) JSON.parse("{'$group': {'_id': {'qzc':'$qzc','qzt':'$qzt'},'z': {'$sum':1}}}");
DBObject project = (DBObject) JSON.parse("{'$project': {'z':1,'difference': { '$eq': [ '$l', '$qzt' ]}}}");
DBObject match = (DBObject) JSON.parse("{'$match': {'difference':true,'l':{'$ne':0}}}");
DBObject sort = (DBObject) JSON.parse("{'$sort': {'z':-1}}");

AggregationOutput output = mongoTemplate.getCollection("events2").aggregate(group, project, match, sort);

db.events2.aggregate(
[
{
"$group":{
"_id":{
"qzc":"$qzc",
"qzt":"$qzt"
},
"z":{
"$sum":1
}
}
},
{
"$project":{
"z":1,
"difference":{
"$eq":[
"$l",
"$qzt"
]
}
}
},
{
"$match":{
"difference":true,
"l":{
"$ne":0
}
}
},
{
"$sort":{
"z":-1
}
}
]
);