我正在尝试查询mongodb集合以获取一个特定的id字段 -

Question

我正在尝试从上次更新（＆＃34; timeSliceStart＆＃34;）行获取_id，该行具有匹配＆＃34; EmployeeName＆＃34;

DBCursor cursor = collection.find(EmployeeName).sort(new BasicDBObject("timeSliceStart", -1)).limit(1);
 while(cursor.hasNext()) {
            String result = cursor.next().get("id"); }

Mongo DB中的数据::

{ "_id" : { "employeeId" : "1234567890", "@objectName" : "FeedMetadata" }, "school" : false, "college" : null, "errorCount" : 0, "errors" : [], "EmployeeName" : "Peter" }

正在打印的结果是： { "employeeId" : "1234567890" , "@objectName" : "FeedMetadata"}

我想要来自_id的employeeId，我尝试了_id.employeeId ;，但它返回了null。 有没有办法只显示employeeId？

我的Java程序 -

  BasicDBObject whereQuery = new BasicDBObject();
    whereQuery.put("EmployeeName", empName);
    DBCursor cursor = collection.find(whereQuery).sort(new BasicDBObject("lastUpdate", -1)).limit(1);
    while(cursor.hasNext()) {
        String result = cursor.next().get("_id").toString();
        System.out.println(result);
    }

Answer 1

您可以像这样更改while循环：

while(cursor.hasNext()) {
    String result = ((HashMap)((BasicDBObject)(cursor.next().get("_id")))).get("employeeId");
    System.out.println(result);
}