如何使用 java 代码转换 mongodb 查询

Question

我是 MongoDB 的新手。我想将此 mongo 数据库查询转换为 java 代码。我已经尝试了一点。但我有一个问题。请，如果有人帮助意味着这对我来说将是一个很大的帮助。提前致谢。

db.getCollection('test').aggregate(
  [{
      $match: {
        "ids": 9999999,
        $or : [{"tags.name":"roja"},{"tags.location":"US"},{"tags.year":2019}]
      }
    },
    {
      '$facet': {
        metadata: [{ $count: "total" }],
        data: [{
          $addFields: {
            "weight": {
              $map: {
                input: "$tags",
                as: "tagsEl",
                in: {
                  "$add": 
                    [              
                      {$cond: [ { $eq: [ '$$tagsEl.roja', 'roja' ] }, 15, 1 ]} ,
                      {$cond: [ { $eq: [ '$$tagsEl.location', 'US' ] }, 10, 1 ]},
                      {$cond: [ { $eq: [ '$$tagsEl.year', 2019 ] }, 5, 1 ]}                    
                    ]
                }
              }
            }
          }
        }, { $skip: 0 }, { $limit: 10 }, { '$sort': { 'weight' : -1 } }]
      }
    }
  ]
)

Answer 1

您可以使用 Studio3T 将您的查询直接转换为 java 代码，除非您对语法不满意。

https://studio3t.com/knowledge-base/articles/query-code/

Answer 2

//Get database
MongoDatabase db = mongoClient.getDatabase("testdb");

//get collection
MongoCollection<Document> testCol = db.getCollection("test");

//prepare a list of aggregation pipeline stages.
List<Bson> aggs = new ArrayList<>();

//each pipeline stage you wrote is in js. the equivalent java syntax is...

//for {key1:value1,key2:value2}
  new Document().append("key1","value1").append("key2","value2")

//for array such as ["abc",1,{key3,value3}]
  Arrays.asList("abc",1,new Document("key3","value3"))


//for example , part of your script can be implemented in java as below.
 aggs.add(
  new Document("$match",//match aggregation pipeline stage
    new Document("ids",9999999)
      .append("$or",Arrays.asList(
        new Document("tags.name","roja"),
        new Document("tags.location","US"),
        new Document("tags.year",2019)
       ))
  )
);
//you can add as many stages as you need to aggs list.
//execute
MongoCursor<Document> cursor = testCol.aggregate(aggs).iterator();
while(cursor.hasNext()){
  Document d = cursor.next();
  //do your operation.
}

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