mysql如何在Java中从mongodb集合返回数据

Question

我有一个MongoDB数据库，其集合如下：

+----------+-------------+
| Field    | Type        |
+----------+-------------+
| sha      | varchar(40) |
| filename | text        | 
+----------+-------------+

我还有一个MySQL数据库，它的表如下所示：

+----------+-------------+
| Field    | Type        |
+----------+-------------+
| sha      | varchar(40) |
| filename | text        | 
+----------+-------------+

MySQL表中的SHA列包含50000条记录，而filename列是空的，我想从上面的MongoDB集合中获取。我想将此表中的SHA键与MongoDB集合中的SHA键进行比较。规则是，如果Mongo集合中存在SHA，则提取与该SHA密钥对应的文件名，并将其插入与本地MySQL中的SHA密钥对应的文件名字段

如何根据MySQL中的sha值返回文件名值？我只是不熟悉MongoDB查询的工作原理，我的MongoDB查询正确吗

我目前编写的代码如下所示：

//Get sha values from mysql and compare with the sha values in mongo and return corresponding filenames
Statement sqlStmt = mysqlConn.createStatement();
HashMap < String, String > shaFileNameMap = new HashMap < String, String > ();

//get sha values from local mysql
String shaQuery = "select * from commit_files";
ResultSet results = sqlStmt.executeQuery(shaQuery);
String sha = null;
String filename = null;

//Store returned sha values in a hashmap
while (results.next()) {
  sha = results.getString("sha");
  filename = results.getString("filename");
  //Store in a map
  shaFileNameMap.put(sha, filename);
}

for (Map.Entry < String, String > entry: shaFileNameMap.entrySet()) {
  String key = entry.getKey();

  //get all filenames matching the list from mongo db and insert into mysql
  DBCollection commits = db.getCollection("commits");
  DBObject query = new BasicDBObject();
  BasicDBObject fields = new BasicDBObject("sha", "" + key + "");
  DBCursor curs = commits.find(query, fields);
  while (curs.hasNext()) {
    DBObject o = curs.next();

    //The code to insert filenames into Mysql goes here
  }
}

Answer 1

我的建议是：使用当前的API：

...
MongoClient client = new MongoClient();
MongoCollection<Document> coll = client .getDatabase("xyz").getCollection("myColl");
...
// in the query loop:
FindIterable<Document> res = coll.find(Filters.eq("sha", key);
// and go through the find iterable which has 0 to many entries

关键是，com。mongodb。客户模型Filters类保存所有您需要的内容，作为创建查询的快捷方式

API文档位于https://api.mongodb.com/java/current/com/mongodb/client/model/Filters.html