I have this code to create a simple .NET .dll. It only returns an int.
But, it is not working inside Java.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ReturnINT
{
public class ReturnINT
{
public static int RetornaInteiro ()
{
try
{
int number = 2;
return number;
}
catch (Exception)
{
return 1;
}
}
}
}
How can I call the method from within Java?
When I Use JNI i have this error IN java:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Dll.RetornaInteiro()V
at Dll.RetornaInteiro(Native Method)
at Dll.main(Dll.java:27)
Check the http://www.javonet.com as well. With one-jar file you can load this dll and call as follows:
Javonet.AddReference("your-lib.dll");
int result = Javonet.getType("ReturnINT").Invoke("RetornaInteiro");
Javonet will automatically load your library in .NET process and give you access to any classes and types contain within it. Next you can get your type and invoke static method. Method results and arguments are automatically translated between JAVA and .NET types. You can pass for example string or bool arguments like that
Boolean arg1 = true;
String arg2 = "test";
Javonet.getType("ReturnINT").Invoke("MethodWithArguments",arg1,arg2);
And they will be translated automatically.
In addition you can also create instance of your type, subscribe events, set/get properties and fields, handle exceptions or even pass value-type arguments. Check the docs for more details:
http://www.javonet.com/quick-start-guide/
PS: I am member of Javonet team. Therefore feel free to ask me any detailed questions regarding native integrations and our product.
You can call it directly: http://jni4net.sourceforge.net/
Or you can call it as an executable.
Related
OK, so I have the C# DLL method:
public void DeletePublisher(string strName)
{
try
{
if (_PublisherData.PublisherDictionary.ContainsKey(strName))
_PublisherData.PublisherDictionary.Remove(strName);
}
catch (Exception ex)
{
SimpleLog.Log(ex);
}
}
It works fine. If there is a exception it is detected and added to the log.
At the moment, the above is called via MFC in my C++ project using a wrapper:
bool CMSATools::DeletePublisher(CString strPublisher)
{
bool bDeleted = false;
if (m_pInterface != nullptr)
{
CComBSTR bstrPublisher = strPublisher.AllocSysString();
throw_if_fail(m_pInterface->DeletePublisher(bstrPublisher));
bDeleted = true;
}
return bDeleted;
}
They both work fine. The issue is that fact that the CPP method currently has no knowledge of the C# method having failed. Now, in this particular instance I know I could change the signature of the DLL method to return false for a exception failure occurring and examine that return value in the CPP file.
But, in other instances I am already using the return value and thus, it would seem for consistency to me, that I pass in a bool bExceptionRaised parameter instead to my methods in the DLL.
That way, I can test that value when the method seemed to complete and if it is false act accordingly.
At the moment my application doesn't realise that an exception occurred and that is confusion.
Can I assume that either of these methodologies are the simplest approach to what I am trying to detect?
Update
Based on the answer provided I have tried to follow this tutorial and I am getting confused. I have tried to follow it and I can't create a CLR DLL and build it that is a bridge to my C# DLL file.
Whilst I appreciate the answer I feel like it is breaking up everything I have worked on since the C# DLL already handles and logs it's exceptions. Whilst I would like to learn how to build this bridge for the future, I still think perhaps at the point in time just changing my signatures is sufficient. Either way, my attempt a basic build of a bridge is failing.
Use a C++/CLI wrapper for the access of the managed component.
With C++/CLI you can directly use the C# component can catch the managed exception and you can throw a native exception or even return true or false... whatever you want.
void DoManagedStuff(SOMEDATA somedata)
{
try
{
auto sm = ConvertToSomeDataToManaged(somedata);
CallManagedCode(sm);
}
catch (Exception^ e)
{
throw CMyNativeException();
}
}
I have a problem running a Gurobi Optimization Model using a C#/.NET library through IronPython.
I have a method to access variables though their name (ie GRBModel.GetVarByName), something like
public GRBVar variable(i,t)
{
try
{
GRBModel M = getModel();
string varname = varname(i,t);
GRBVar var = M.GetVarByName(varname);
return var;
}
catch (GRBException ex)
{
System.Console.WriteLine(ex.ToString());
throw new GRBException(ex.ToString());
}
}
The problem is that on my IronPython script, when I try to access a non existing variable, nothing happens... the message doesnt appear on the console. What I'm doing wrong???
I think you're missing a return statement somewhere; if you catch the exception, the method does not return. (Doesn't the C# compiler error in that case?)
If this method is just for IronPython, you could just let the exception pass through to IronPython and deal with it there.
According to this page in the Gurobi .NET Reference Manual, GRBException inherits from the .NET Exception class. To obtain the error message from an Exception based class you should use the Message property rather than the ToString() method, which by default normally displays only the class name for reference classes.
In other words, change the catch clause to:
catch (GRBException ex)
{
System.Console.WriteLine(ex.Message);
}
Alternatively, you could output the ErrorCode property which is specific to the GRBException class.
I am working on an extension for a project that will allow hosting the CLR inside the core application. With this I plan to allow this extension to manage managed extensions that it loads/unloads inside itself. That being said, I need to use separate AppDomains to ensure unloading is possible.
Currently, I am able to get the domains setup and get the plugin file loaded but at that point I'm stuck. I'm not sure how to call functions inside the domains loaded assembly at will and so on.
Here is my loading setup so far, minus error checking and such:
ICorRuntimeHost* lpRuntimeHost = NULL;
CorBindToRuntimeEx( L"v4.0.30319", L"wks", 0, CLSID_CorRuntimeHost, IID_PPV_ARGS( &lpRuntimeHost ) );
lpRuntimeHost->Start();
// File data read from disk.
// Dll file just CreateFile/ReadFile and insert into pluginFileData.
CComSafeArray<BYTE> pluginFileData;
IUnknown* lpUnknown = NULL;
lpRuntimeHost->CreateDomain( wstrPlugin.c_str(), NULL, &lpUnknown );
CComPtr<_AppDomain> appDomain = NULL;
lpUnknown->QueryInterface( &appDomain.p );
CComPtr<_Assembly> appAssembly = NULL;
hResult = appDomain->Load_3( pluginFileData, &appAssembly );
I have a class library that all plugins must reference and use in order to be considered a plugin. Which so far is nothing more than a base class to inherit:
namespace FrameworkAPI
{
public class IFrameworkPlugin
{
public override bool Initialize(IntPtr interfaceObj)
{
return false;
}
}
}
And then an extension would reference that class library and use that as its base:
namespace ClassLibrary1
{
public class Main : IFrameworkPlugin
{
public override bool Initialize(IntPtr interfaceObj)
{
// Return true to stay loaded.
return true;
}
}
}
What I am stuck at is how to do a few things:
How can I obtain the main class but as the base to invoke methods in the base that allow the main class to still handle?
How can I ensure that the main class inherits the base so I can ensure its a valid plugin file?
How I can freely invoke methods from the C++ side to fire events in the C# plugin.
For the firing events, the C++ plugin will call more things in the C# plugins once they are loaded, such as rendering events, command handling, etc.
Most of the examples I find online are specific to requiring the entire C# side to be static which I don't want. Also most do not use separate AppDomains and rather all execute in the default. I don't want this since it limits being able to unload a specific plugin.
If any other info is missing and needed feel free to let me know.
I resolved this issue by using a COM exposed interface for the C# side of things.
I have placed the FrameworkAPI inside a separate DLL and exposed it's main interface to COM then reference it in the plugins that will use it.
With it compiled with COM enabled, I can import the .tlb generated file to use the interface in C++ easily.
I have written a dll in C#, offering a class for use. The dll is called by a C program that I have written. (It’s a plugin to some program. I have to write the plugin’s code in C, but I want to use the functionality of .NET, therefore the dll).
In the dll, I want to open up a stream and do other stuff that should be persistent between two calls to the dll. That is represented in the following code by the private member Connector.
namespace myCSharpDll
{
// the c++ program calls this methods
public interface IAccess
{
double Initialize();
double Timestep(double time, double[] values);
...
}
// E is the beginning of another program my dll should connect to, therefore the names
public class EAccess : IAccess
{
// EConnector is another class I defined in the same dll
private EConnector Connector;
public double InitializeE()
{
Connector = new EPConnector();
}
public double Timestep(double time, double[] values)
{
return Connector.Connect();
}
When I make a call to InitializeE() and later one to Timestep() the Connector oject points to NULL.
What do I have to do that when I call Timestep() from my C code, that I can access the before created instance of Connector?
I probably search in the wrong direction at all. Any tips are appreciated.
If I am not wrong you want to maintain a single object throughout the use of dll in c. If that is the case try something similar to singleton pattern.
http://en.wikipedia.org/wiki/Singleton_pattern
What singleton emphazises is you create only single object for a class and use it to perform all the work you need. Basically you might need a function that does something like this,
public class EAccess : IAccess
{
private static EConnector Connector
public EConnector getConnector(){
if(Connector == null){
Connector = new EConnector();
}
return Connector;
}
public double Timestep(double time, double[] values)
{
return getConnector().Connect();
}
};
Even though this is not the traditional way of doing things using singleton but I think it still does the work. I may be wrong. Please correct me if I have misunderstood something.
Thanks SLaks for asking for my C/C++ code. That is where the problem was located. It was simpler than I thought. I found the mistake while putting together the code to show you.
I know that C and C++ is not the same, the plugin structure is just a little weird. Most of the code was generated by a wizard. I just had to fill in my code. It's a cpp file, but the code seems to be C. Well, I think that is off topic.
Here it is, I extraced the most important lines.
// the dll is connected via COM, using the type library file that regasm generated
#import "[path]\myCSharpDll.tlb" raw_interfaces_only
using namespace myCSharpDll;
static void OnActivate (IfmDocument, Widget);
//off topic: this are the weird lines the wizard put in my way
#ifdef __cplusplus
extern "C"
#endif /* __cplusplus */
// when the plugin is called by the host program, this function is called
static void OnActivate (IfmDocument pDoc, Widget button)
{
InitializeIntermediate(pDoc);
Timestep1(...);
}
static void InitializeIntermediate(IfmDocument pDoc)
{
// Initialize COM.
HRESULT hr = CoInitialize(NULL);
IEPAccessPtr pIEPAccess(__uuidof(EPAccess));
double result = -1;
pIEPAccess->InitializeEP (&result);
...
}
static void Timestep1(...)
{
IEPAccessPtr pIEPAccess(__uuidof(EPAccess));
double result = -1.1;
pIEPAccess->Timestep (...);
...
// now I get a wrong result back here, because this call leads to nowhere as
// the connector object in the dll is void
}
I realized that I am requesting a second instance with that line
IEPAccessPtr pIEPAccess(__uuidof(EPAccess));
So I changed that pointer to one single instance and everything is fine. Thanks for your comments!
Consider following piece of code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace RemotingNonVirtualCall
{
class Program
{
static void Main(string[] args)
{
var domain = AppDomain.CreateDomain("Second Domain");
A extA = (A)domain.CreateInstanceAndUnwrap(typeof(A).Assembly.FullName, typeof(A).FullName);
Console.WriteLine(extA.CurrentDomain());
}
}
[Serializable]
sealed class A : MarshalByRefObject
{
public string CurrentDomain()
{
return AppDomain.CurrentDomain.FriendlyName;
}
}
}
Method A::CurrentDomain is non-virtual, class A is sealed. But CLR intercepts method call and redirect it to another instance. How it is possible? Is it some sort of voodoo magic? Does CLR make some exception in method calling for object inherited from MarshalByRefObject class? How is it performed?
Thanks for advance.
It's essentially magic, i.e. the ability to do this is built into the .NET runtime. The good news is that your code can also do this, if it needs to: http://msdn.microsoft.com/en-us/library/system.runtime.remoting.proxies.realproxy.aspx
The JIT compiler is keenly aware that it generates code for a proxy. You can have a look-see with the SSCLI20 source code, clr\src\vm\jithelpers.cpp, search for "proxy".