Java 11 support

[Dmunch04]

Hi. I'm trying to create an engine.io server with Java JDK 11.0.5. Altough I seem to get errors about the AsyncListener class, which was also removed after Java 8. Are there any plans to make it support Java 8+?

[trinopoty]

AsyncListener is a part of the java servlet api. Are you sure you have the proper dependencies?
What server are you using?

[Dmunch04]

Here's the error I'm getting:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/AsyncListener
	at java.base/java.lang.ClassLoader.defineClass1(Native Method)
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
	at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
	at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:800)
	at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:698)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:621)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	at org.TeamName.ChatApp.Server.Server.<init>(Server.java:43)
	at org.TeamName.ChatApp.App.main(App.java:15)
Caused by: java.lang.ClassNotFoundException: javax.servlet.AsyncListener
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	... 11 more

Process finished with exit code 1

And the code that was the reason I got those errors:

EngineIoServer server = new EngineIoServer();

And here's my dependencies in my pom:

<dependencies>
  <!-- java-express -->
  <dependency>
    <groupId>com.github.Simonwep</groupId>
    <artifactId>java-express</artifactId>
    <version>caef9738b4</version>
  </dependency>
  <!-- - -->

  <!-- socket.io client -->
  <dependency>
    <groupId>io.socket</groupId>
    <artifactId>socket.io-client</artifactId>
    <version>1.0.0</version>
  </dependency>
  <!-- - -->

  <!-- engine.io server -->
  <dependency>
    <groupId>engine.io</groupId>
    <artifactId>server</artifactId>
    <version>1.0</version>
  </dependency>
  <!-- - -->

  <!-- socket.io server -->
  <dependency>
    <groupId>socket.io</groupId>
    <artifactId>server</artifactId>
    <version>1.0</version>
  </dependency>
  <!-- - -->
</dependencies>

And as you might notice, both the engine.io and socket.io server has been built from your sources by me. So yeah I've just built them myself to try and fix the error.

[trinopoty]

Ah I see.
This library is not meant to be used as a standalone server. It can only be used within a web server such as Tomcat or Jetty.

[Dmunch04]

Aha. I wanted to use it together with java-express, but I guess that's not possible?

[trinopoty]

I guess not unless you can run java-express inside a java web server.
This library has heavy dependencies (basically based around) the java servlet api.

[Dmunch04]

Well could you please provide a simple example of how to use Jetty to end up with a socket.io server?

[trinopoty]

Please look at this example.
It can be run on any server viz. Tomcat, Jetty, etc.

[Dmunch04]

Well I can't create a new EngineIoServer class instance, without getting that error

[trinopoty]

You would need to add dependency on javax:javaee-api:7.0. But, like I said, it'll only run in a server implementation such as Tomcat, Jetty, etc.

[Dmunch04]

So even for you, if you just do

EngineIoServer server = new EngineIoServer();

you'll also get that error.

And would I add that dependency to the engine.io-server or my project's pom?

[Dmunch04]

Because I can see that in the example you sent, it does that:
https://github.com/jeevaengg21/engine.io/blob/master/src/main/java/com/jee/engineio/sample/EngineIoServlet.java#L32

[Dmunch04]

Also how would I run the server? I can't seem to find any exact location where they run the server. I might just be blind

[trinopoty]

Yes, you need to add the dependency in your project. But, simply adding it in will bring a whole lot of problems too unless you're deploying your project on a java server.
Alternatively, you can use a Jetty embedded server. You can find examples for that here.

[Dmunch04]

Yeah. That was kind of what I was hoping that you had a simple example for. I found this: https://github.com/socketio/engine.io-server-java/blob/master/docs/using.rst#jetty-server
But I don't know if that's still gonna work?

[Dmunch04]

Like a simple Jetty example with engine.io and socket.io