如何使用mongocxx c ++驱动程序递归生成Mongodb文档? [英] How to generate Mongodb documents recursively using mongocxx c++ driver?
问题描述
如何使用mongocxx c ++驱动程序递归生成Mongodb文档? 1.我使用mongocxx c ++驱动程序v.3和c ++ 11. 2.这是我的main.cpp方法，该方法解析十六进制字符串并生成mongocxx代码，如下所示: 控制台:$ ./主要剖析0x160301012c01000128030340c70e243001b96d8c 和输出:
How to generate Mongodb documents recursively using mongocxx c++ driver? 1. I use mongocxx c++ driver v.3 and c++11. 2. Here is my main.cpp method, which parses hex string and generate mongocxx code like this: console:$ ./main dissect 0x160301012c01000128030340c70e243001b96d8c and the output:
<< "MainType" << bsoncxx::builder::stream::open_document
<< "TLSRecord" << bsoncxx::builder::stream::open_document
<< "type"<< "16"
<< "version"<< "0301"
<< "length"<< "012C"
<< "hsMsg" << bsoncxx::builder::stream::open_document
<< "type"<< "01"
<< "length"<< "000128"
<< "clientHello" << bsoncxx::builder::stream::open_document
<< "version"<< "0303"
<< "random"<< "40C70E243001B96D8C"
<< "session_id_length"<< ""
<< bsoncxx::builder::stream::close_document
<< bsoncxx::builder::stream::close_document
<< bsoncxx::builder::stream::close_document
-
此后，我需要将其推入mongodb中.
After this I needed to push it in mongodb.
-
从解剖方法形式main.cpp调用连接方法 十六进制字符串解析后调用mongodb连接
Call connection method from dissect method form main.cpp Call mongodb connection after hex string parsing
创建mongodbConnection:
Create the mongodbConnection:
调用MongodbMapper将生成的代码映射到db
Call MongodbMapper to map generated code to db
调用GenerateDocument自动生成 连接-> Mapp->生成->插入
Call GenerateDocument to generate it automatically Connect -> Mapp -> Generate -> Insert
在这里，我堆积如山，尝试编译时出现错误.
And Here I got stacked, got error when try to compile it.
src/MongodbMapper.cpp:76:6: note: candidate function not viable: no known conversion from 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context> >' to
'bsoncxx::builder::stream::document &' for 3rd argument
void generateDocument(DataUnit& node, int level, bsoncxx::builder::stream::document& doc) {
src/MongodbMapper.cpp:76:6: note: candidate function not viable: no known conversion from 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context> >' to
'bsoncxx::builder::stream::document &' for 3rd argument
void generateDocument(DataUnit& node, int level, bsoncxx::builder::stream::document& doc) {
推荐答案
很难确定没有看到您发布的细分受众群的上下文，但是看起来您遇到的问题与流构建器上的<<运算符.实际上，流生成器的名称不正确；它不是典型的C ++单词意义上的流"，因为<<运算符的输出类型有时会与左侧操作数不同.特别是，无论何时使用open_document或close_document之类的表达式，表达式输出的类型都会与左侧操作数不同.因此，通常需要存储这些表达式之一的输出.
It's hard to be sure without seeing the context of the segment you posted, but it looks like the issue you're running into is with the output type of the << operator on the stream builder. The stream builder is actually misnamed; it isn't a "stream" in the typical C++ sense of the word, as the output type of the << operator will sometime be different than the left-hand-side operand. In particular, whenever you use something like open_document or close_document, the type that expression outputs will be different than what the left-hand-side operand is. Because of this, you'll generally need to store the output of one of those expressions.
由于在这种情况下流构建器经常引起混乱，因此通常最好改用基本构建器.基本构建器的语法稍微有些冗长，但要犯一个细微的错误要困难得多，而且当您犯错时，编译器错误消息也更容易理解.
Because of the confusion that the stream builder often causes in cases like this, it's generally preferable to use the basic builder instead. While the basic builder's syntax is a little more verbose, it's much harder to make a subtle mistake with it, and when you do make a mistake, the compiler error messages are much easier to understand.
以下是使用基本构建器构建相同文档的方法:
Here's how you would build up the same document with the basic builder:
#include <bsoncxx/builder/basic/document.hpp>
#include <bsoncxx/builder/basic/kvp.hpp>
#include <bsoncxx/builder/basic/sub_document.hpp>
using bsoncxx::builder::basic::kvp;
using bsoncxx::builder::basic::sub_document;
bsoncxx::builder::basic::document doc;
// Build the document
doc.append(kvp("MainType", [](sub_document sub_doc1) {
sub_doc1.append(kvp("TLSRecord", [](sub_document sub_doc2) {
sub_doc2.append(kvp("type", "16"),
kvp("version", "0301"),
kvp("length", "012C"),
kvp("hsMsg", [](sub_document sub_doc3) {
sub_doc3.append(kvp("type", "01"),
kvp("length", "000128"),
kvp("clientHello", [](sub_document sub_doc4) {
sub_doc4.append(
kvp("version", "0303"),
kvp("random", "40C70E243001B96D8C"),
kvp("session_id_length", ""));
}));
}));
}));
}));
// Get a view of the document being built and do something with it.
do_something_with_document_view(doc.view());
// Extract the document from the builder and do something with it.
do_something_with_owned_document(doc.extract());
bsoncxx::builder::basic::document::append采用任意数量的kvp(键-值对)并将其附加到构建器.对于诸如字符串之类的基本类型，您可以仅将值作为第二个参数传递.要构建子文档，请使用lambda作为第二个参数，该参数采用bsoncxx::builder::basic::sub_document，然后以相同的方式附加到该子文档构建器.
bsoncxx::builder::basic::document::append takes a arbitrary number of kvp's (key-value pairs) and appends them to the builder. For basic types like strings, you can just pass the value as the second argument. To build up a subdocument, use a lambda as the second argument that takes a bsoncxx::builder::basic::sub_document and then append to that subdocument builder in same the same way.
要从构建器中获取文档，可以使用view()或extract()方法. view()返回bsoncxx::document::view()，这是文档的未拥有视图；构建者需要在使用视图的整个过程中保持活动状态. extract()返回bsoncxx :: document :: value，它是一个拥有的值；调用extract()时，构建器将重置为空状态.
To get the document out from the builder, you can either use the view() or extract() methods. view() returns a bsoncxx::document::view(), which is an unowned view of the document; the builder needs to remain alive for the entire time the view is used. extract() returns a bsoncxx::document::value, which is an owned value; when extract() is called, the builder is reset back to the empty state.
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