Qt5.7不能加载MySql驱动问题.(需要重新编译驱动)

港控/mmm° 2022-07-18 00:28 285阅读 0赞

首先贴上我遇到的问题,如下:

QSqlDatabase: QMYSQL driver not loaded

QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

Unable to open database

在解决这个问题的时候,首先在网上查询了各种解决方案,都尝试过,但是其中遇到的一些小问题,总是找不到解决方法,最终在"Stack Overflow"上提问得到了答案,故此记录一下,一遍以后备用,也希望能帮助到一些人.

环境:   ubantu16.04 + Qt5.7 + MySql5.7

# 分析 #

**1**.首先确定自己是否安好装了MySql(没有安装则先安装)  
安装方法:(该链接里面同时也包含卸载方法)

[http://blog.csdn.net/yimi0903/article/details/11800713][http_blog.csdn.net_yimi0903_article_details_11800713]

其次执行以下命令,看是否已安装以下选项:

sudo apt-get install libmysqlclient-dev

**2.** 进入驱动所在目录:

cd  /ProgramFiles/Qt5.7.0/5.7/gcc\_64/plugins/sqldrivers

**3**. ls 查看目录里面的文件:

cc@1whispers:~/ProgramFiles/Qt5.7.0/5.7/gcc\_64/plugins/sqldrivers$ ls  
libqsqlite.so  libqsqlmysql.so  libqsqlpsql.so

**4.** 执行命令查看 libqsqlmysql.so 的依赖:

ldd libqsqlmysql.so

显示如下:

linux-vdso.so.1 =>  (0x00007ffcb64e2000)
    	libmysqlclient_r.so.16 => not found
    	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fea06463000)
    	libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007fea0622a000)
    	libnsl.so.1 => /lib/x86_64-linux-gnu/libnsl.so.1 (0x00007fea06011000)
    	libssl.so.10 => /usr/lib/x86_64-linux-gnu/libssl.so.10 (0x00007fea05dba000)
    	libQt5Sql.so.5 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007fea05b74000)
    	libQt5Core.so.5 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007fea05459000)
    	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fea0523c000)
    	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fea04eb9000)
    	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fea04bb0000)
    	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fea0499a000)
    	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fea045d0000)
    	libnss3.so => /usr/lib/x86_64-linux-gnu/libnss3.so (0x00007fea0428a000)
    	libnssutil3.so => /usr/lib/x86_64-linux-gnu/libnssutil3.so (0x00007fea0405d000)
    	libplc4.so => /usr/lib/x86_64-linux-gnu/libplc4.so (0x00007fea03e57000)
    	libnspr4.so => /usr/lib/x86_64-linux-gnu/libnspr4.so (0x00007fea03c18000)
    	libicui18n.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.56 (0x00007fea0377d000)
    	libicuuc.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.56 (0x00007fea033c5000)
    	libicudata.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.56 (0x00007fea019e2000)
    	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fea017dd000)
    	libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007fea015db000)
    	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fea013d3000)
    	libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fea010c2000)
    	/lib64/ld-linux-x86-64.so.2 (0x0000560757219000)
    	libplds4.so => /usr/lib/x86_64-linux-gnu/libplds4.so (0x00007fea00ebd000)
    	libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007fea00c4d000)

在此会发现一个问题:   libmysqlclient\_r.so.16 => not found,说明没有这个依赖项,所以现在我们要解决的是这个依赖.

**5.**查看自己所有的 libmysqlclient.so

cc@1whispers:~$ locate libmysqlclient.so

/home/cc/Desktop/libmysqlclient.so.20  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so.20  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so.20.3.0

可知到我们的依赖有这些.

# 编译MySql驱动 #

注:通常这种情况最好应该先看看官网文档

[http://doc.qt.io/qt-5/sql-driver.html\#qmysql][http_doc.qt.io_qt-5_sql-driver.html_qmysql]

**1**.首先要确定自己在安装Qt的时候安装了源码,如果没有安装源码,则需要重装Qt,切记装的时候记得选上源码那一项.

**2**.进入到源码中MySql驱动的源码中

cd /ProgramFiles/Qt5.7.0/5.7/Src/qtbase/src/plugins/sqldrivers/mysql

路径是各自安装qt的路径而来.

**3**. 执行编译:

qmake->make->make install

执行过程:

sudo /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/bin/qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient\_r" mysql.pro

sudo make

sudo make install

在查看依赖 ldd libqsqlmysql.so ,则会看到已有依赖库.

再去运行程序,则会显示成功连接数据库.

Database connection established

这是记得要sudo make clean清理一下之前编译的中间文件.

# 可能出现的问题 #

**1.**执行qmake的时候: qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient\_r" mysql.pro这样的命令是用的默认的qmake文件,这样如果没有Qt4的SDK,则会出错,所以需要用我们自己安装Qt时路劲下的qmake.

sudo /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/bin/qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient\_r" mysql.pro

需要加上sudo,不然会出现 not permit的错误,即没有权限,所以需要用root权限.

**2**.在执行make的时候,也需要用到root权限.不然会出现以下错误:

注: 我本人就是死在这里,因为没有用root权限,但是出现错误又不懂什么原因,迷茫了2天,终于解决.

home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/bin/moc -DQT\_NO\_MTDEV -DQT\_NO\_LIBUDEV -DQT\_NO\_TSLIB -DQT\_NO\_LIBINPUT -DQT\_NO\_CAST\_TO\_ASCII -DQT\_NO\_CAST\_FROM\_ASCII -DQT\_NO\_EXCEPTIONS -D\_LARGEFILE64\_SOURCE -D\_LARGEFILE\_SOURCE -DQT\_NO\_DEBUG -DQT\_PLUGIN -DQT\_SQL\_LIB -DQT\_CORE\_LIB -I/home/cc/ProgramFiles/Qt5.7.0/5.7/Src/qtbase/mkspecs/linux-g++ -I/home/cc/ProgramFiles/Qt5.7.0/5.7/Src/qtbase/src/plugins/sqldrivers/mysql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtSql/5.7.0 -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtSql/5.7.0/QtSql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtCore/5.7.0 -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtCore/5.7.0/QtCore -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtSql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc\_64/include/QtCore -I/usr/include/c++/5 -I/usr/include/x86\_64-linux-gnu/c++/5 -I/usr/include/c++/5/backward -I/usr/lib/gcc/x86\_64-linux-gnu/5/include -I/usr/local/include -I/usr/lib/gcc/x86\_64-linux-gnu/5/include-fixed -I/usr/include/x86\_64-linux-gnu -I/usr/include main.cpp -o .moc/main.moc  
moc: Cannot create .moc/main.moc  
Makefile:652: recipe for target '.moc/main.moc' failed  
make: \*\*\* \[.moc/main.moc\] Error 1

**3**. 使用证确方式(sudo make)执行后肯能会出现以下问题:

-lQt5Sql -lQt5Core -lpthread  
    /usr/bin/ld: cannot find -lmysqlclient_r
    collect2: error: ld returned 1 exit status
    Makefile:114: recipe for target '../../../../plugins/sqldrivers/libqsqlmysql.so' failed
    make: *** [../../../../plugins/sqldrivers/libqsqlmysql.so] Error 1

可知,我们没有了lmysqlclient\_r相关的文件:即没有libmysqlclient\_r.so等文件;但是在之前分析的时候,知道我们有

/home/cc/Desktop/libmysqlclient.so.20  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so.20  
/usr/lib/x86\_64-linux-gnu/libmysqlclient.so.20.3.0

所以要去链接出lmysqlclient\_r相关的文件;

cd /usr/lib/x86_64-linux-gnu/ ln -s libmysqlclient.so.20.3.0 libmysqlclient_r.so.20.3.0 ln -s libmysqlclient.so.20 libmysqlclient_r.so.20 ln -s libmysqlclient.so libmysqlclient_r.so

这样在去执行sudo make命令,则会成功.

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[http_blog.csdn.net_yimi0903_article_details_11800713]: http://blog.csdn.net/yimi0903/article/details/11800713
[http_doc.qt.io_qt-5_sql-driver.html_qmysql]: http://doc.qt.io/qt-5/sql-driver.html#qmysql