如何使用 java 驱动程序在 mongodb 中的嵌入式文档中推送评论

Question

我有以下文件： </p> <pre><code>enter code here

{ “_id”：ObjectId（“56c49b52a5b24ba2a979a964”），

"FirstName" : "satvik",
"LastName" : "ponakala",
"Major" : "Information Assurance",
"RoomPost" : [
    {
        "postId" : 1,
        "title" : "I have a room to share at Garden Square",
        "comments" : [
            {
                "comment1" : " i want to join",
                "author" : "ashish"
            },
            {
                "comment2" : " already booked",
                "author" : "puneeth"
            }
        ]
    },
    {
        "postId" : 2,
        "title" : "I have a room to share at Ansley Falls",
        "comments" : [
            {
                "comment1" : " How many can stay",
                "author" : "sandeep"
            },
            {
                "comment2" : "can i come there next sunday??",
                "author" : "sandeep"
            }
        ]
    }
]

}

如何添加新评论{ "comment3":"push comment from java", "author":"Java" } 在 post ID 下的评论部分：1 来自 java

Answer 1

你需要匹配 postId 1，然后将新评论推送到 "comments"，像这样：

db.[your collection name].update({"RoomPost" :{$elemMatch :{"postId" : 1}}}, {$push : {"RoomPost.$.comments": {"comment3" :"some comment"}}})

用 java 驱动程序编写它很容易，'update' 部分是这样的：

BasicDBObject  update = new BasicDBObject("$push", new BasicDBObject("RoomPost.$.comments",new BasicDBObject("comment3" ,"some comment" ) ))

希望对您有所帮助。