qt odbc plugin build unsuccessful - qt

Question

I developed an application along the lines of the SQL Browser example provided with QT in the Demos and Examples section. My development machine is Windows XP (visual studio compiler was used) and the application works well on it. It is able to connect to an external database (MySQL), and I am able browse through tables. I used the QODBC driver for connections. However when I deploy the executable (with all required .dll files) in another computer without QT, it says that I need to provide for the database drivers. I read the documentation and realized that I need to build a PlugIn for QODBC drivers.
First I looked at an example Plugin (Echo Plugin Example) given at http://doc.qt.digia.com/4.6/tools-echoplugin.html. Then I followed the instructions in http://doc.qt.digia.com/4.6/sql-driver.html#qodbc.
cd %QTDIR%\src\plugins\sqldrivers\odbc
qmake odbc.pro
nmake
The above commands built qsqlodbc4.dll. However, I am not successful in developing a Plugin for my application. Here are my steps, and the compilation output:
Created project odbcplugin.pro (see script below) under directory /odbcpluginTest
TEMPLATE = subdirs
SUBDIRS = sqlbrowser \
odbc
CONFIG += release
# install
target.path = $$PWD
sources.path = $$PWD
sources.files = $$SOURCES $$HEADERS $$RESOURCES $$FORMS
INSTALLS += target sources
Created subdirectories: /odbc, /sqlbrowser, /plugins
Inside the directroy /odbcpluginTest /odbc/
(i). Copied odbc.pro and suitably modified the paths and file names (for example, a file originally named as main.cpp has been renamed as mainODBC.cpp to avoid confusing with the file named main.cpp inside /sqlbrowser). See the scripts below:
TEMPLATE = lib
INCLUDEPATH += ../sqlbrowser
SOURCES = mainODBC.cpp
TARGET = qsqlodbc
DESTDIR = ../plugins
CONFIG += release
include(qsql_odbc.pri)
include(qsqldriverbase.pri)
sources.files = $$SOURCES $$HEADERS $$RESOURCES $$FORMS
INSTALLS += target sources
(ii). The file odbcinterface.h that describes the plugin interface is included as a header in odbc.pro. However, it is actually placed inside the directory /sqlbrowser. Hence, the line INCLUDEPATH += ../sqlbrowser is included in the above script.
(iii). Also, copied all related project files (qsql_odbc.pri, qsqldriverbase.pri, qpluginbase.pri, qt_targets.pri). Suitably modified the paths in all project files (there may be mistakes in here).
(iv). The header (qsql_odbc.h) and source (qsql_odbc.cpp) files of qsql_odbc.pri have also been copied.
Inside the directory /odbcpluginTest /sqlbrowser/
(i). Copied sqlbrowser.pro and all related files.
(ii). Created the header file odbcinterface.h that describes the plugin interface (see below) and added it to the HEADERS in sqlbrowser.pro.
#ifndef ODBCINTERFACE_H
#define ODBCINTERFACE_H
#include <QString>
#include <QtSql/qsqldriver.h>
class OdbcInterface
{
public:
virtual ~OdbcInterface() {}
virtual QSqlDriver* create(const QString &) = 0;
virtual QStringList keys() const = 0;
};
QT_BEGIN_NAMESPACE
Q_DECLARE_INTERFACE(OdbcInterface,
"developed similar to com.trolltech.Plugin.EchoInterface/1.0");
QT_END_NAMESPACE
#endif // ODBCINTERFACE_H
iii. Also, modified the browser.h file by adding the lines
#include "odbcinterface.h"
private:
bool loadPlugin();
OdbcInterface *odbcInterface;
Public:
void TestCase1();
iv. Also, modified the browser.cpp file by adding the function definitions:
bool Browser::loadPlugin()
{
QDir pluginsDir(qApp->applicationDirPath());
#if defined(Q_OS_WIN)
pluginsDir.cdUp();
pluginsDir.cdUp();
#endif
pluginsDir.cd("plugins");
foreach (QString fileName, pluginsDir.entryList(QDir::Files)) {
QPluginLoader pluginLoader(pluginsDir.absoluteFilePath(fileName));
QObject *pluginI = pluginLoader.instance();
if (pluginI) {
odbcInterface = qobject_cast<OdbcInterface *>(pluginI);
if (odbcInterface)
return true;
}
}
return false;
}
void Browser::TestCase1()
{
loadPlugin();
QStringList list;
list = odbcInterface->keys();
QMessageBox msgBox;
if(list.length() >0)
{
msgBox.setText("Test1 success");
}
else
{
msgBox.setText("Test1 failure");
}
msgBox.exec();
}
Testing:
In browser.cpp file, the constructor Browser::Browser(QWidget *parent) was modified by appending a call to void Browser::TestCase1()
Compile Output:
15:09:18: Running build steps for project odbcplugin...
15:09:18: Configuration unchanged, skipping qmake step.
15:09:18: Starting: "C:\QtSDK\QtCreator\bin\jom.exe"
cd sqlbrowser\ && C:\QtSDK\QtCreator\bin\jom.exe -nologo -j 2 -f Makefile
C:\QtSDK\QtCreator\bin\jom.exe -nologo -j 2 -f Makefile.Debug
cd odbc\ && C:\QtSDK\QtCreator\bin\jom.exe -nologo -j 2 -f Makefile
C:\QtSDK\QtCreator\bin\jom.exe -nologo -j 2 -f Makefile.Release
link /LIBPATH:"c:\QtSDK\Desktop\Qt\4.8.1\msvc2010\lib" /NOLOGO /DYNAMICBASE /NXCOMPAT /INCREMENTAL:NO /DLL /MANIFEST /MANIFESTFILE:"release\qsqlodbc.intermediate.manifest" /VERSION:4.81 /OUT:..\plugins\qsqlodbc4.dll #C:\DOCUME~1\SHAINE~1\LOCALS~1\Temp\qsqlodbc4.dll.5076.0.jom
Creating library ..\plugins\qsqlodbc4.lib and object ..\plugins\qsqlodbc4.exp
mainODBC.obj : error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall QODBCDriverPlugin::metaObject(void)const " (?metaObject#QODBCDriverPlugin##UBEPBUQMetaObject##XZ)
mainODBC.obj : error LNK2001: unresolved external symbol "public: virtual void * __thiscall QODBCDriverPlugin::qt_metacast(char const *)" (?qt_metacast#QODBCDriverPlugin##UAEPAXPBD#Z)
mainODBC.obj : error LNK2001: unresolved external symbol "public: virtual int __thiscall QODBCDriverPlugin::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall#QODBCDriverPlugin##UAEHW4Call#QMetaObject##HPAPAX#Z)
..\plugins\qsqlodbc4.dll : fatal error LNK1120: 3 unresolved externals
jom 1.0.6 - empower your cores
command failed with exit code 1120
command failed with exit code 2
command failed with exit code 2
15:09:19: The process "C:\QtSDK\QtCreator\bin\jom.exe" exited with code 2.
Error while building project odbcplugin (target: Desktop)
When executing build step 'Make'