Restlet proxy generation fails with latest GWT 2.5.0-RC1 - gwt

Upgraded to GWT 2.5.0-RC1 and the proxy generation for Restlet breaks - I have the latest release 2.1-RC6 in my project. This is the stack trace :
java.lang.NoSuchMethodException: com.google.gwt.user.rebind.rpc.SerializableTypeOracleBuilder.<init>(com.google.gwt.core.ext.TreeLogger, com.google.gwt.core.ext.PropertyOracle, com.google.gwt.core.ext.typeinfo.TypeOracle)
at java.lang.Class.getConstructor0(Class.java:2706)
at java.lang.Class.getDeclaredConstructor(Class.java:1985)
at org.restlet.rebind.ClientProxyGenerator.getSerializableTypeOracleBuilder2_2(ClientProxyGenerator.java:767)
at org.restlet.rebind.ClientProxyGenerator.generateSerializers(ClientProxyGenerator.java:569)
at org.restlet.rebind.ClientProxyGenerator.generateProxy(ClientProxyGenerator.java:500)
at org.restlet.rebind.ClientProxyGenerator.generate(ClientProxyGenerator.java:242)
The actual exception gets thrown here :
private SerializableTypeOracleBuilder getSerializableTypeOracleBuilder2_2()
throws Exception {
SerializableTypeOracleBuilder result = null;
Constructor<SerializableTypeOracleBuilder> c = null;
c = SerializableTypeOracleBuilder.class.getDeclaredConstructor(
TreeLogger.class, PropertyOracle.class, TypeOracle.class);
result = c.newInstance(getLogger(), getContext().getPropertyOracle(),
getTypeOracle());
return result;
}
This following call seems problematic, though I do not see why :
c = SerializableTypeOracleBuilder.class.getDeclaredConstructor(
TreeLogger.class, PropertyOracle.class, TypeOracle.class);
Somebody got Restlet GWT working with the latest GWT 2.5.0-rc1 ??
UPDATE: issue opened #647

I just checked the POMs for the following GWT versions of Restlet:
http://maven.restlet.org/org/restlet/gwt/org.restlet/2.2-SNAPSHOT/
http://maven.restlet.org/org/restlet/gwt/org.restlet/2.1.1/
and they all have dependencies on version 2.2 of GWT.

That's the problem when using internal classes: SerializableTypeOracleBuilder's constructor no longer takes a TypeOracle argument, but a GeneratorContext.
http://code.google.com/p/google-web-toolkit/source/browse/releases/2.5/user/src/com/google/gwt/user/rebind/rpc/SerializableTypeOracleBuilder.java#782
That was already the case in GWT 2.4 though (with the experimental GeneratorContextExt instead): http://code.google.com/p/google-web-toolkit/source/browse/releases/2.4/user/src/com/google/gwt/user/rebind/rpc/SerializableTypeOracleBuilder.java#747
and even GWT 2.3: http://code.google.com/p/google-web-toolkit/source/browse/releases/2.3/user/src/com/google/gwt/user/rebind/rpc/SerializableTypeOracleBuilder.java#763
In other words, Restlet still depends on a 18 months old version, namely GWT 2.2: http://code.google.com/p/google-web-toolkit/source/browse/releases/2.2/user/src/com/google/gwt/user/rebind/rpc/SerializableTypeOracleBuilder.java#757

Thanks for reporting this issue. The 2.1 and master branches have been updated.

Related

Getting error log while previewing report from Jasper [duplicate]

I am getting a NoClassDefFoundError when I run my Java application. What is typically the cause of this?
While it's possible that this is due to a classpath mismatch between compile-time and run-time, it's not necessarily true.
It is important to keep two or three different exceptions straight in our head in this case:
java.lang.ClassNotFoundException This exception indicates that the class was not found on the classpath. This indicates that we were trying to load the class definition, and the class did not exist on the classpath.
java.lang.NoClassDefFoundError This exception indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it. This is different than saying that it could not be loaded from the classpath. Usually this indicates that we previously attempted to load a class from the classpath, but it failed for some reason - now we're trying to use the class again (and thus need to load it, since it failed last time), but we're not even going to try to load it, because we failed loading it earlier (and reasonably suspect that we would fail again). The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError (indicating a failure in the static initialization block) or any number of other problems. The point is, a NoClassDefFoundError is not necessarily a classpath problem.
This is caused when there is a class file that your code depends on and it is present at compile time but not found at runtime. Look for differences in your build time and runtime classpaths.
Here is the code to illustrate java.lang.NoClassDefFoundError. Please see Jared's answer for detailed explanation.
NoClassDefFoundErrorDemo.java
public class NoClassDefFoundErrorDemo {
public static void main(String[] args) {
try {
// The following line would throw ExceptionInInitializerError
SimpleCalculator calculator1 = new SimpleCalculator();
} catch (Throwable t) {
System.out.println(t);
}
// The following line would cause NoClassDefFoundError
SimpleCalculator calculator2 = new SimpleCalculator();
}
}
SimpleCalculator.java
public class SimpleCalculator {
static int undefined = 1 / 0;
}
NoClassDefFoundError In Java
Definition:
Java Virtual Machine is not able to find a particular class at runtime which was available at compile time.
If a class was present during compile time but not available in java classpath during runtime.
Examples:
The class is not in Classpath, there is no sure shot way of knowing it but many times you can just have a look to print System.getproperty("java.classpath") and it will print the classpath from there you can at least get an idea of your actual runtime classpath.
A simple example of NoClassDefFoundError is class belongs to a missing JAR file or JAR was not added into classpath or sometimes jar's name has been changed by someone like in my case one of my colleagues has changed tibco.jar into tibco_v3.jar and the program is failing with java.lang.NoClassDefFoundError and I were wondering what's wrong.
Just try to run with explicitly -classpath option with the classpath you think will work and if it's working then it's a sure short sign that someone is overriding java classpath.
Permission issue on JAR file can also cause NoClassDefFoundError in Java.
Typo on XML Configuration can also cause NoClassDefFoundError in Java.
when your compiled class which is defined in a package, doesn’t present in the same package while loading like in the case of JApplet it will throw NoClassDefFoundError in Java.
Possible Solutions:
The class is not available in Java Classpath.
If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause java.lang.NoClassDefFoundError, see examples and scenario section for detailed discussion.
Check for java.lang.ExceptionInInitializerError in your log file. NoClassDefFoundError due to the failure of static initialization is quite common.
Because NoClassDefFoundError is a subclass of java.lang.LinkageError it can also come if one of it dependency like native library may not available.
Any start-up script is overriding Classpath environment variable.
You might be running your program using jar command and class was not defined in manifest file's ClassPath attribute.
Resources:
3 ways to solve NoClassDefFoundError
java.lang.NoClassDefFoundError Problem patterns
I have found that sometimes I get a NoClassDefFound error when code is compiled with an incompatible version of the class found at runtime. The specific instance I recall is with the apache axis library. There were actually 2 versions on my runtime classpath and it was picking up the out of date and incompatible version and not the correct one, causing a NoClassDefFound error. This was in a command line app where I was using a command similar to this.
set classpath=%classpath%;axis.jar
I was able to get it to pick up the proper version by using:
set classpath=axis.jar;%classpath%;
One interesting case in which you might see a lot of NoClassDefFoundErrors is when you:
throw a RuntimeException in the static block of your class Example
Intercept it (or if it just doesn't matter like it is thrown in a test case)
Try to create an instance of this class Example
static class Example {
static {
thisThrowsRuntimeException();
}
}
static class OuterClazz {
OuterClazz() {
try {
new Example();
} catch (Throwable ignored) { //simulating catching RuntimeException from static block
// DO NOT DO THIS IN PRODUCTION CODE, THIS IS JUST AN EXAMPLE in StackOverflow
}
new Example(); //this throws NoClassDefFoundError
}
}
NoClassDefError will be thrown accompanied with ExceptionInInitializerError from the static block RuntimeException.
This is especially important case when you see NoClassDefFoundErrors in your UNIT TESTS.
In a way you're "sharing" the static block execution between tests, but the initial ExceptionInInitializerError will be just in one test case. The first one that uses the problematic Example class. Other test cases that use the Example class will just throw NoClassDefFoundErrors.
This is the best solution I found so far.
Suppose we have a package called org.mypackage containing the classes:
HelloWorld (main class)
SupportClass
UtilClass
and the files defining this package are stored physically under the directory D:\myprogram (on Windows) or /home/user/myprogram (on Linux).
The file structure will look like this:
When we invoke Java, we specify the name of the application to run: org.mypackage.HelloWorld. However we must also tell Java where to look for the files and directories defining our package. So to launch the program, we have to use the following command:
I was using Spring Framework with Maven and solved this error in my project.
There was a runtime error in the class. I was reading a property as integer, but when it read the value from the property file, its value was double.
Spring did not give me a full stack trace of on which line the runtime failed.
It simply said NoClassDefFoundError. But when I executed it as a native Java application (taking it out of MVC), it gave ExceptionInInitializerError which was the true cause and which is how I traced the error.
#xli's answer gave me insight into what may be wrong in my code.
I get NoClassFoundError when classes loaded by the runtime class loader cannot access classes already loaded by the java rootloader. Because the different class loaders are in different security domains (according to java) the jvm won't allow classes already loaded by the rootloader to be resolved in the runtime loader address space.
Run your program with 'java -javaagent:tracer.jar [YOUR java ARGS]'
It produces output showing the loaded class, and the loader env that loaded the class. It's very helpful tracing why a class cannot be resolved.
// ClassLoaderTracer.java
// From: https://blogs.oracle.com/sundararajan/entry/tracing_class_loading_1_5
import java.lang.instrument.*;
import java.security.*;
// manifest.mf
// Premain-Class: ClassLoadTracer
// jar -cvfm tracer.jar manifest.mf ClassLoaderTracer.class
// java -javaagent:tracer.jar [...]
public class ClassLoadTracer
{
public static void premain(String agentArgs, Instrumentation inst)
{
final java.io.PrintStream out = System.out;
inst.addTransformer(new ClassFileTransformer() {
public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
String pd = (null == protectionDomain) ? "null" : protectionDomain.getCodeSource().toString();
out.println(className + " loaded by " + loader + " at " + new java.util.Date() + " in " + pd);
// dump stack trace of the thread loading class
Thread.dumpStack();
// we just want the original .class bytes to be loaded!
// we are not instrumenting it...
return null;
}
});
}
}
The technique below helped me many times:
System.out.println(TheNoDefFoundClass.class.getProtectionDomain().getCodeSource().getLocation());
where the TheNoDefFoundClass is the class that might be "lost" due to a preference for an older version of the same library used by your program. This most frequently happens with the cases, when the client software is being deployed into a dominant container, armed with its own classloaders and tons of ancient versions of most popular libs.
Java ClassNotFoundException vs NoClassDefFoundError
[ClassLoader]
Static vs Dynamic class loading
Static(Implicit) class loading - result of reference, instantiation, or inheritance.
MyClass myClass = new MyClass();
Dynamic(Explicit) class loading is result of Class.forName(), loadClass(), findSystemClass()
MyClass myClass = (MyClass) Class.forName("MyClass").newInstance();
Every class has a ClassLoader which uses loadClass(String name); that is why
explicit class loader uses implicit class loader
NoClassDefFoundError is a part of explicit class loader. It is Error to guarantee that during compilation this class was presented but now (in run time) it is absent.
ClassNotFoundException is a part of implicit class loader. It is Exception to be elastic with scenarios where additionally it can be used - for example reflection.
In case you have generated-code (EMF, etc.) there can be too many static initialisers which consume all stack space.
See Stack Overflow question How to increase the Java stack size?.
Two different checkout copies of the same project
In my case, the problem was Eclipse's inability to differentiate between two different copies of the same project. I have one locked on trunk (SVN version control) and the other one working in one branch at a time. I tried out one change in the working copy as a JUnit test case, which included extracting a private inner class to be a public class on its own and while it was working, I open the other copy of the project to look around at some other part of the code that needed changes. At some point, the NoClassDefFoundError popped up complaining that the private inner class was not there; double-clicking in the stack trace brought me to the source file in the wrong project copy.
Closing the trunk copy of the project and running the test case again got rid of the problem.
I fixed my problem by disabling the preDexLibraries for all modules:
dexOptions {
preDexLibraries false
...
I got this error when I add Maven dependency of another module to my project, the issue was finally solved by add -Xss2m to my program's JVM option(It's one megabyte by default since JDK5.0). It's believed the program does not have enough stack to load class.
In my case I was getting this error due to a mismatch in the JDK versions. When I tried to run the application from Intelij it wasn't working but then running it from the command line worked. This is because Intelij was attempting to run it with the Java 11 JDK that was setup but on the command line it was running with the Java 8 JDK. After switching that setting under File > Project Structure > Project Settings > Project SDK, it worked for me.
Update [https://www.infoq.com/articles/single-file-execution-java11/]:
In Java SE 11, you get the option to launch a single source code file
directly, without intermediate compilation. Just for your convenience,
so that newbies like you don't have to run javac + java (of course,
leaving them confused why that is).
NoClassDefFoundError can also occur when a static initializer tries to load a resource bundle that is not available in runtime, for example a properties file that the affected class tries to load from the META-INF directory, but isn’t there. If you don’t catch NoClassDefFoundError, sometimes you won’t be able to see the full stack trace; to overcome this you can temporarily use a catch clause for Throwable:
try {
// Statement(s) that cause(s) the affected class to be loaded
} catch (Throwable t) {
Logger.getLogger("<logger-name>").info("Loading my class went wrong", t);
}
I was getting NoClassDefFoundError while trying to deploy application on Tomcat/JBOSS servers. I played with different dependencies to resolve the issue, but kept getting the same error. Marked all javax.* dependencies as provided in pom.xml, And war literally had no Dependency in it. Still the issue kept popping up.
Finally realized that src/main/webapps/WEB-INF/classes had classes folder which was getting copied into my war, so instead of compiled classes, this classes were getting copied, hence no dependency change was resolving the issue.
Hence be careful if any previously compiled data is getting copied, After deleting classes folder and fresh compilation, It worked!..
If someone comes here because of java.lang.NoClassDefFoundError: org/apache/log4j/Logger error, in my case it was produced because I used log4j 2 (but I didn't add all the files that come with it), and some dependency library used log4j 1. The solution was to add the Log4j 1.x bridge: the jar log4j-1.2-api-<version>.jar which comes with log4j 2. More info in the log4j 2 migration.
This error can be caused by unchecked Java version requirements.
In my case I was able to resolve this error, while building a high-profile open-source project, by switching from Java 9 to Java 8 using SDKMAN!.
sdk list java
sdk install java 8u152-zulu
sdk use java 8u152-zulu
Then doing a clean install as described below.
When using Maven as your build tool, it is sometimes helpful -- and usually gratifying, to do a clean 'install' build with testing disabled.
mvn clean install -DskipTests
Now that everything has been built and installed, you can go ahead and run the tests.
mvn test
I got NoClassDefFound errors when I didn't export a class on the "Order and Export" tab in the Java Build Path of my project. Make sure to put a checkmark in the "Order and Export" tab of any dependencies you add to the project's build path. See Eclipse warning: XXXXXXXXXXX.jar will not be exported or published. Runtime ClassNotFoundExceptions may result.
It could also be because you copy the code file from an IDE with a certain package name and you want to try to run it using terminal. You will have to remove the package name from the code first.
This happens to me.
Everyone talks here about some Java configuration stuff, JVM problems etc., in my case the error was not related to these topics at all and had a very trivial and easy to solve reason: I had a wrong annotation at my endpoint in my Controller (Spring Boot application).
I have had an interesting issue wiht NoClassDefFoundError in JavaEE working with Liberty server. I was using IMS resource adapters and my server.xml had already resource adapter for imsudbJXA.rar.
When I added new adapter for imsudbXA.rar, I would start getting this error for instance objects for DLIException, IMSConnectionSpec or SQLInteractionSpec.
I could not figure why but I resolved it by creating new server.xml for my work using only imsudbXA.rar. I am sure using multiple resource adapters in server.xml is fine, I just had no time to look into that.
I had this error but could not figure out the solution based on this thread but solved it myself.
For my problem I was compiling this code:
package valentines;
import java.math.BigInteger;
import java.util.ArrayList;
public class StudentSolver {
public static ArrayList<Boolean> solve(ArrayList<ArrayList<BigInteger>> problems) {
//DOING WORK HERE
}
public static void main(String[] args){
//TESTING SOLVE FUNCTION
}
}
I was then compiling this code in a folder structure that was like /ProjectName/valentines
Compiling it worked fine but trying to execute: java StudentSolver
I was getting the NoClassDefError.
To fix this I simply removed: package valentines;
I'm not very well versed in java packages and such but this how I fixed my error so sorry if this was already answered by someone else but I couldn't interpret it to my problem.
My solution to this was to "avail" the classpath contents for the specific classes that were missing. In my case, I had 2 dependencies, and though I was able to compile successfully using javac ..., I was not able to run the resulting class file using java ..., because a Dynamic class in the BouncyCastle jar could not be loaded at runtime.
javac --classpath "ext/commons-io-2.11.0;ext/bc-fips-1.0.2.3" hello.java
So at compile time and by runtime, the JVM is aware of where to fetch Apache Commons and BouncyCastle dependencies, however, when running this, I got
Error: Unable to initialize main class hello
Caused by: java.lang.NoClassDefFoundError:
org/bouncycastle/jcajce/provider/BouncyCastleFipsProvider
And I therefore manually created a new folder named ext at the same location, as per the classpath, where I then placed the BouncyCastle jar to ensure it would be found at runtime. You can place the jar relative to the class file or the jar file as long as the resulting manifest has the location of the jar specified. Note I only need to avail the one jar containing the missing class file.
Java was unable to find the class A in runtime.
Class A was in maven project ArtClient from a different workspace.
So I imported ArtClient to my Eclipse project.
Two of my projects was using ArtClient as dependency.
I changed library reference to project reference for these ones (Build Path -> Configure Build Path).
And the problem gone away.
I had the same problem, and I was stock for many hours.
I found the solution. In my case, there was the static method defined due to that. The JVM can not create the another object of that class.
For example,
private static HttpHost proxy = new HttpHost(proxyHost, Integer.valueOf(proxyPort), "http");
I got this message after removing two files from the SRC library, and when I brought them back I kept seeing this error message.
My solution was: Restart Eclipse. Since then I haven't seen this message again :-)

ESType error when ModelDrivenControllerBase is using to call MDrivenEcoSpaceAndModelForNetStandard

a code MyController:ModelDrivenControllerBase<EcoProject1EcoSpace> in the mvc or webapi netcore project shows a error "the type 'MDrivenTemplateProj.EcoProject1EcoSpace' cannot be used as type parameter 'ESType' in the generic type or method 'ModelDrivenControllerBase<ESType>'. There is no implicit reference conversion from 'MDrivenTemplateProj.EcoProject1EcoSpace' to 'Eco.Handles.DefaultEcospace" + annoying request to add ref to the 'MDriven.Handles.netStandard, version=7.0.0.0, culture=neutral, publickeytoken=null'. (always version 7.0.0.0!)
Could you please advise how to avoid such kind of errors?
I'm trying to develop the webapi netcore 3.1 app that has ref to MDrivenEcoSpaceAndModelForNetStandard project using the NetFramework 4.x. experience.
Seems that is it wrong way for the netcore project.
Thank you!
Brand new MDriven packages on nuget targeting .netStandard2.1 and .net5 available now.
They have correct build version numbers, and are more granular in packages than the old Eco package.
https://wiki.mdriven.net/index.php/MVC
https://www.nuget.org/packages?q=MDriven*
Old style still valid:
ref to the MDrivenEcoSpaceAndModelForNetStandard project in your netcore webapi
leave ControllerBase as a base class for your MVC controller
create and activate new ecospace in the constructor of your controller
_es = new MDrivenTemplateProj.EcoProject1EcoSpace();_es.Active = true;
you can call CreateFromViewModel method if you want to use VMs, ex.
var vmc = Eco.ViewModel.Runtime.ViewModelHelper.CreateFromViewModel("SampleViewModel", this._es, null, false);
Manual fixes that are still required in MDrivenEcoSpaceAndModelForNetStandard project:
EcoProject1EcoSpace.Designer.cs - this.persistenceMapperSharer1.MapperProviderTypeName auto generated value is incorrect
EcoProject1PMP.Designer.cs - this.EcoSpaceTypeName auto generated value is incorrect
be ready that your build in VS EcoProject modeller will not be able to start persistence after the fixes above. It will show you "No suitable constructor found" message

webClient issue - Between ReactorClientHttpConnector and httpClient

I am facing a problem with versions , first let me explain the problem.
I have the below code :
public WebClient createWebClient() throws SSLException {
SslContext sslContext = SslContextBuilder
.forClient()
.trustManager(InsecureTrustManagerFactory.INSTANCE)
.build();
HttpClient httpClient = HttpClient.create().secure(t -> t.sslContext(sslContext));
return WebClient.builder().baseUrl(endpointURL)
.clientConnector(new ReactorClientHttpConnector(httpClient))
.filter(errorHandlingFilter())
.build();
}
with spring-web version 5.2.3 and netty version 0.9.3 the part with the clientConnector is working fine.
Now the version I have is 5.0.11 (ONLY) and then this part of the code stops to work with the error :
incompatible types: reactor.netty.http.client.HttpClient cannot be converted to java.util.functi
on.Consumer<? super reactor.ipc.netty.http.client.HttpClientOptions.Builder>
Is there any alternative with the older version of spring-web?
Thanks in advance =)
I don't think this is possible. The HttpClientOptions has been removed from reactor-netty in its 0.8.x generation, and you're effectively trying to use a 2 years old Spring Framework generation with a 9 months old release.
The Spring team is trying hard to maintain compatibility, but in the case of reactor netty, this is still a project in its 0.x phase and API changes/repackaging are still expected.

Static type checking error for groovy collection.addAll

This message is also posted on grails mailing list.
In addition to my earlier question I downloaded the grails source from github.
Building via documented gradlew install works (almost) perfect. Than I imported the whole project into Eclipse. And with a bit fighting groovy plugins and "project - workspace-groovy-compiler-issues" I only have a few issues left, all boiling down to java Collection modification in groovy classes. For instance in PluginBuildSettings.groovy:
List<Resource> artefactResourcesList = []
...
artefactResources.addAll compileScopePluginInfo.artefactResources
which gives an error:
Groovy:[Static type checking] - Cannot call java.util.List#addAll(java.util.Collection ) with arguments [java.util.Set ]
I really don't see what the issue may be.
I tried changing the artefactResources declaration in PluginScopeInfo from:
Set<Resource> artefactResources = []
to:
Set<Object> artefactResources = []
which takes away error above, but introduces some other problems let alone the unittests. I'm not hindered with extensive groovy knowledge but it looks all perfect valid to me.
I'm using ggts:
Groovy/Grails Tool Suite
Version: 3.1.0.RELEASE
Build Id: 201210061306
groovy-compiler: 2.0.4.xx -20120921
On mac os x 8.2
java 6.0._37
groovy compiler: 2.0 (workspace and project).
With my favorite search engine I found a reference to grails bug 5516, which is solved but it looks resurected
Type checker fails verification of generic types with addAll
Fixed in 2.0 rc 3,

MEF - Migration from .NET 3.5 to .NET 4.0

I've got an easy sample from the internet that works fine in the .NET 3.5 framework using System.ComponentModel.Composition.dll version v2.0.50727
I've changed the project definition and changed the target to .NET 4.0 and it works perfect.
When I replace the v2.0.50727 version of the above .dll to the latest version which is v4.0.30319 I get an error that complains during the composition of the container. The code where it break is as follows:
private void LoadPlugins() {
var catalog = new AssemblyCatalog(Assembly.GetExecutingAssembly());
var container = new CompositionContainer(catalog);
container.ExportsChanging += new EventHandler(container_ExportsChanging);
var batch = new CompositionBatch();
batch.AddPart(this);
container.Compose(batch); // throws Exception
}
And the exception is the following:
System.ComponentModel.Composition.ChangeRejectedException was unhandled
Message=The composition remains unchanged. The changes were rejected because of the following error(s): The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.
1) More than one export was found that matches the constraint '((exportDefinition.ContractName == "MefTutorial.IPlugin") AndAlso (exportDefinition.Metadata.ContainsKey("ExportTypeIdentity") AndAlso "MefTutorial.IPlugin".Equals(exportDefinition.Metadata.get_Item("ExportTypeIdentity"))))'.
Resulting in: Cannot set import 'MefTutorial.PluginConsumer._myPlugins (ContractName="MefTutorial.IPlugin")' on part 'MefTutorial.PluginConsumer'.
Element: MefTutorial.PluginConsumer._myPlugins (ContractName="MefTutorial.IPlugin") --> MefTutorial.PluginConsumer
What do I need to do to migrate to the .NET 4.0 concerning MEF?
Could it be that another project still references the .net 3.5 version? The error message says that there are two exports of type IPlugin, which I'm quite certain of means that finds both the 3.5 and 4.0 version of the dll.
Check that only the 4.0 version of MefTutorial is referenced and/or present.
OK, I found the problem. Apparently in the previous version the notation was as mentioned in my previous comment, but in the new .NET 4.0 version the syntax for import should be:
code>
[ImportMany(typeof(IPlugin))]
internal List _myPlugins { get; set; }
Notice the use of List and ImportMany instead of IList and Import.