[英]Retrieve fields of all documents in mongodb collection
我正在尝试检索所有文档的所有字段并在 Mongo 集合中嵌入文档。 这是一个文档的示例:
{
"_id": {
"$oid": "53b309def468718462e0c390"
},
"customer": {
"companyName": "Vins et alcools Chevalier",
"contactName": "Paul Henriot",
},
"employee": {
"employeeId": 5,
"firstName": "Steven",
"lastName": "Buchanan"
},
"orderItems": [
{
"productName": "Queso Cabrales",
"unitPrice": 14,
"quantity": 12
},
{
"productName": "Singaporean Hokkien Fried Mee",
"unitPrice": 9.8,
"quantity": 10
}
],
"orderId": 10248,
"orderDate": {
"$date": "1996-07-04T07:00:00.000Z"
},
"requiredDate": {
"$date": "1996-08-01T07:00:00.000Z"
},
"shippedDate": {
"$date": "1996-07-16T07:00:00.000Z"
},
"shipVia": "Federal Shipping",
"freightCost": 32.38
}
这是我的代码和 output:
MongoCursor<Document> cursor;
MongoCollection<Document> collection = database.getCollection("test");
cursor = collection.find().iterator();
try {
while (cursor.hasNext()) {
//System.out.println(cursor.next().toJson());
System.out.println(cursor.next().get("key"));
}
} finally {
cursor.close();
}
这是输出:
null null null null null ...
我只想要名称部分,但它不起作用。
我正在使用 java 驱动程序 3.12.4 和 mongodb v4.2
保护你。
尝试这个:
private void printFields(){
MongoCursor<Document> cursor;
MongoCollection<Document> collection = database.getCollection("user");
cursor = collection.find().iterator();
try {
while (cursor.hasNext()) {
//System.out.println(cursor.next().toJson());
for (Map.Entry<String, Object> entry : cursor.next().entrySet())
{
System.out.println(entry.getKey() + "/" + entry.getValue());
}
}
} finally {
cursor.close();
}
}
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