Qt：自定义的sqldrivers dll（QtCipherSqlitePlugin）无法加载，提示sqlitecipher.dll is not a Qt plugin (metadata not found)
自定义的sqldrivers dll无法加载。添加测试代码：
qDebug() << "sqlite drivers: " << QSqlDatabase::drivers();
QString driverPath = QCoreApplication::applicationDirPath() + "/sqldrivers/sqlitecipher.dll";
auto l = QPluginLoader(driverPath);
if (!l.load()) {
qDebug() << "Failed to load SQLite DLL:" << driverPath;
qDebug() << "Error:" << l.errorString();
}
qDebug() << "sqlite drivers: " << QSqlDatabase::drivers();
返回错误提示： sqlitecipher.dll is not a Qt plugin (metadata not found)
比对代码发现，因为此前无法编译通过，误删了关键的metadata代码：
Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QSqlDriverFactoryInterface" FILE "SqliteCipherDriverPlugin.json")恢复此行代码，并删除#if (QT_VERSION >= 0x050000)的版本判断，否则还会提示以下错误：
1> QtCipherSqlitePlugin\src\main.cpp: note: No relevant classes found. No output generated.
1>main.cpp
1>main.obj : error LNK2001: 无法解析的外部符号 "public: virtual struct QMetaObject const * __cdecl SqliteCipherDriverPlugin::metaObject(void)const " (?metaObject@SqliteCipherDriverPlugin@@UEBAPEBUQMetaObject@@XZ)
1>main.obj : error LNK2001: 无法解析的外部符号 "public: virtual void * __cdecl SqliteCipherDriverPlugin::qt_metacast(char const *)" (?qt_metacast@SqliteCipherDriverPlugin@@UEAAPEAXPEBD@Z)
1>main.obj : error LNK2001: 无法解析的外部符号 "public: virtual int __cdecl SqliteCipherDriverPlugin::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@SqliteCipherDriverPlugin@@UEAAHW4Call@QMetaObject@@HPEAPEAX@Z)提示 SqliteCipherDriverPlugin.json 文件找不到，修改：
Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QSqlDriverFactoryInterface" FILE "src/SqliteCipherDriverPlugin.json")问题解决。
转载请注明来源，谢谢。
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