Unable to construct Instance of specified SQLExceptionConverter

Question

我是 Nhibernate 的新手，我正在尝试修复我们项目中出现的警告，但我无法理解异常是从哪个方法或类引发的。

   WARN - Unable to construct instance of specified SQLExceptionConverter System.MissingMethodException: No parameterless constructor defined for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at NHibernate.Bytecode.ActivatorObjectsFactory.CreateInstance(Type type)
   at NHibernate.Exceptions.SQLExceptionConverterFactory.ConstructConverter(String converterClassName, IViolatedConstraintNameExtracter violatedConstraintNameExtracter)

我在 app.config 文件中找到了以下配置，并试图在那里放置断点并在该类中进行调试，但它甚至没有到达那里

 <property name="sql_exception_converter">OdbcExceptionConverter, Solution.Folder.ProjectName.Project</property>

有什么关于如何调查这个的建议吗？

ODBC转换器类：

public class OdbcExceptionConverter : ISQLExceptionConverter
    {
        public Exception Convert(AdoExceptionContextInfo adoExceptionContextInfo)
        {
            var odbcException = ADOExceptionHelper.ExtractDbException(adoExceptionContextInfo.SqlException) as OdbcException;

            if (odbcException == null)
            {
                return SQLStateConverter.HandledNonSpecificException(adoExceptionContextInfo.SqlException, adoExceptionContextInfo.Message, adoExceptionContextInfo.Sql);
            }

            if (odbcException.Errors.Any())
            {
                foreach (var error in odbcException.Errors)
                {
                    switch (((OdbcError)error).SQLState)
                    {
                        case "23000":
                            return new ConstraintViolationException(adoExceptionContextInfo.Message, odbcException, adoExceptionContextInfo.Sql, null);
                    }
                }
            }

            return SQLStateConverter.HandledNonSpecificException(adoExceptionContextInfo.SqlException, adoExceptionContextInfo.Message, adoExceptionContextInfo.Sql);
        }
    }

Answer 1

System.MissingMethodException：没有为此对象定义无参数构造函数。

所以只需将默认公共构造函数添加到您的转换器类。像这样的东西：

public class OdbcExceptionConverter : ISQLExceptionConverter
{
//...

public OdbcExceptionConverter() //<-- Added default parametless constructor
{}

//...
}

如果它不起作用，您可以通过设置自定义激活器来进一步调试它。像这样的东西：

//Somewhere before session factory is created:
NHibernate.Cfg.Environment.ObjectsFactory = new DebugActivatorFactory();

public class DebugActivatorFactory : ActivatorObjectsFactory, IObjectsFactory
{
    object IObjectsFactory.CreateInstance(System.Type type)
    {
        try
        {
            return base.CreateInstance(type);
        }
        catch (Exception e)
        {
            throw new ApplicationException("Failed to create instance of " + type.AssemblyQualifiedName);
        }
    }
}

也许你有多个

OdbcExceptionConverter

类，而你修改了错误的一个。我看不出为什么有可用公共 ctor 的其他公共课会抛出这样的异常。