前言
mongocxx官网地址 http://mongocxx.org/?jmp=docs
本文的安装版本是：mongocxx-r3.2.0.tar.gz 。
参考文档安装过程 http://mongocxx.org/mongocxx-v3/installation/ 。根据文档过程安装，由于系统不一致，可能会遇到各种问题，笔者就一路坎坷。
Linux系统信息：Linux 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-2 (2016-04-08) x86_64 GNU/Linux
1 开始安装
1.1 安装最新版的mongoDB C driver
mongocxx是基于mongo-c-driver的，所以需要先下载安装最新版本的 mongo-c-driver。此时最新版本是 1.13.0.tar.gz 。
参考链接：http://mongoc.org/libmongoc/current/installing.html 。本文所有内容都是采用源码安装的方式。
根据文档要求，cmake需要是3.2或之后的版本。camke --version发现系统的cmake还停留在2.x版本。先升级一下cmake。
1.1.1 升级cmake到最近版本
wget https://cmake.org/files/v3.12/cmake-3.12.3.tar.gz tar -xzf cmake-3.12.3.tar.gz
cd cmake-3.12.3 ./configure sudo make && make install cmake --version
其中，cmake --version检查一下最终的cmake版本。
mongo-c-driver的cmake过程：
wget https://github.com/mongodb/mongo-c-driver/releases/download/1.13.0/mongo-c-driver-1.13.0.tar.gz tar -xzf mongo-c-driver-1.13.0.tar.gz
mkdir cmake-build
cd cmake-build cmake -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF -DCMAKE_BUILD_TYPE=Release ..
NOTE：这里要特别注意cmake的输出，会提示你系统还缺少什么库（NOT FOUND），请不要无视。笔者的mongo-c-driver就安装了两遍。
例如，openssl和snappy没有安装正确。虽然最终cmake和make不会报错，但是最后面用mongocxx的时候会提示ssl错误，不能连接mongodb。
附上cmake的部分输出：
-- Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the system variable OPENSSL_ROOT_DIR (missing: OPENSSL_CRYPTO_LIBRARY OPENSSL_INCLUDE_DIR) -- Searching for sasl/sasl.h -- Found in /usr/include -- Searching for libsasl2 -- Found /usr/lib/x86_64-linux-gnu/libsasl2.so -- Detected parameters: accept (int, struct sockaddr *, socklen_t *) -- Searching for compression library header snappy-c.h -- Not found (specify -DCMAKE_INCLUDE_PATH=/path/to/snappy/include for Snappy compression) -- No ICU library found, SASLPrep disabled for SCRAM-SHA-256 authentication. -- If ICU is installed in a non-standard directory, define ICU_ROOT as the ICU installation path. -- SSL disabled -- Compiling against Cyrus SASL -- Configuring done -- Generating done -- Build files have been written to: /home/yyln2745/studyplace/mongo-c-driver-1.13.0/cmake-build
如果SSL disabled的话，后面你写的代码应该会报错：The SCRAM_SHA_1 authentication mechanism requires libmongoc built with ENABLE_SSL: generic server error 。
1.1.2 openssl问题
先确定是否安装了openssl。直接在shell输入openssl命令，或者查看目录：/usr/local/ssl 是否有东西。确定没有则需要安装一下了。
export OPENSSL_ROOT_DIR=/usr/local/ssl export OPENSSL_CRYPTO_LIBRARY=/usr/local/ssl/lib export OPENSSL_INCLUDE_DIR=/usr/local/ssl/include/
1.1.4 安装snappy
snappy用来压缩的。虽然不知道不安装会有什么问题，但是不想像SSL一样，遇到问题了再回头来修，将上面cmake提到的not found的都解决。安装命令：
wget https://github.com/google/snappy/tarball/master tar -xzf master cd google-snappy-ea660b5/cmake cmake ..
// 暂停一下 make sudo make install
在make前，我们需要先编辑一下CMakeCache.txt，修改CMAKE_CXX_FLAGS:STRING=-fPIC 。为什么要加 -fPIC 呢？因为不这样的话，待会mongo-c-driver执行make时，应该会报以下错误：
/usr/bin/ld: /usr/local/lib/libsnappy.a(snappy.cc.o): relocation R_X86_64_32 against `.rodata' can not be used when making a shared object; recompile with -fPIC /usr/local/lib/libsnappy.a: error adding symbols: Bad value collect2: error: ld returned 1 exit status src/libmongoc/CMakeFiles/mongoc_shared.dir/build.make:1277: recipe for target 'src/libmongoc/libmongoc-1.0.so.0.0.0' failed make[2]: *** [src/libmongoc/libmongoc-1.0.so.0.0.0] Error 1 CMakeFiles/Makefile2:1678: recipe for target 'src/libmongoc/CMakeFiles/mongoc_shared.dir/all' failed make[1]: *** [src/libmongoc/CMakeFiles/mongoc_shared.dir/all] Error 2 Makefile:151: recipe for target 'all' failed make: *** [all] Error 2
关于更多 fPIC 的知识，可另行学习，建议了解一下。
1.1.5 安装ICU
wget http://download.icu-project.org/files/icu4c/4.2.1/icu4c-4_2_1-src.tgz tar -xzf icu4c-4_2_1-src.tgz cd source ./configure make sudo make install
1.1.6 最后make
最后一步，接着make & make install mongo-c-driver。
make sudo make install
如果还出现如下错误：
[66%]Linking C executable test-libmongoc /usr/bin/ld: /usr/local/ssl/lib/libcrypto.a(dso_dlfcn.o): undefined reference to symbol 'dlclose@@GLIBC_2.2.5' //lib/x86_64-linux-gnu/libdl.so.2: error adding symbols: DSO missing from command line collect2: error: ld returned 1 exit status src/libmongoc/CMakeFiles/test-libmongoc.dir/build.make:1563: recipe for target 'src/libmongoc/test-libmongoc' failed make[2]: *** [src/libmongoc/test-libmongoc] Error 1 CMakeFiles/Makefile2:1376: recipe for target 'src/libmongoc/CMakeFiles/test-libmongoc.dir/all' failed make[1]: *** [src/libmongoc/CMakeFiles/test-libmongoc.dir/all] Error 2 Makefile:151: recipe for target 'all' failed make: *** [all] Error 2
这是mongo-c-driver测试样例编译错误，我们可以选择直接干掉，方法为编辑mongo-c-driver的CMakeCache.txt文件，修改ENABLE_TESTS:BOOL=OFF，或者在cmake的时候修改，命令如下，注意TEST后面有S：
cmake -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF -DCMAKE_BUILD_TYPE=Release -DENABLE_TESTS=OFF ..
安装mongocxx
wget -OL https://github.com/mongodb/mongo-cxx-driver/archive/r3.3.1.tar.gz tar -xzf r3.3.1.tar.gz cd mongo-cxx-driver-r3.3.1/build cmake -DCMAKE_BUILD_TYPE=Release -DBSONCXX_POLY_USE_MNMLSTC=1 -DCMAKE_INSTALL_PREFIX=/usr/local .. make EP_mnmlstc_core make
sudo make install
其中，/usr/local是与前面的mongodb c driver同目录， DBSONCXX_POLY_USE_MNMLSTC=1 or DBSONCXX_POLY_USE_BOOST=1
这里问题不大。
代码测试
测试代码如下：
#include <iostream> #include <bsoncxx/builder/stream/document.hpp> #include <bsoncxx/json.hpp> #include <mongocxx/client.hpp> #include <mongocxx/instance.hpp> int main(int, char**) { mongocxx::instance inst{};
//下面uri 请替换成真实数值。 mongocxx::uri yace_uri{"mongodb://test_username:test_pwd@test_ip:test_port/?authSource=test_db"}; mongocxx::options::client client_options; if (yace_uri.ssl()) { std::cout << "ssl-----------\n"; } else { std::cout << "no-ssl\n"; } mongocxx::client conn{yace_uri}; mongocxx::database db = conn["test_db"]; mongocxx::collection gift_test = db["gift_test"]; bsoncxx::stdx::optional<bsoncxx::document::value> res = gift_test.find_one({}); if (res) std::cout << bsoncxx::to_json(*res) << std::endl; return 0; }
编译命令：
c++ --std=c++11 test.cpp \ -I/usr/local/include/mongocxx/v_noabi -I/usr/local/include/libmongoc-1.0 \ -I/usr/local/include/bsoncxx/v_noabi -I/usr/local/include/libbson-1.0 \ -L/usr/local/lib -lmongocxx -lbsoncxx -Wl,-rpath,/usr/local/lib
添加“-Wl,-rpath,/usr/local/lib” 是因为运行时报错：error while loading shared libraries: libmongocxx.so._noabi。
参考链接：
https://jira.mongodb.org/browse/CXX-1425 for preior question.
http://blog.51cto.com/elephantliu/563298
https://blog.csdn.net/furzoom/article/details/70843664 https://stackoverflow.com/questions/6562403/i-dont-understand-wl-rpath-wl
总结
本文介绍了mongocxx的安装过程，主要记录其中可能遇到的问题和解决过程。