I have a simple WebSocket endpoint defined, it is just echoing the data sent by
the client. Here's the code.
@ServerEndpoint(value="/websocket",
decoders={ListStringDecoder.class},
encoders={ListStringEncoder.class})
public static class Server {
@OnMessage
public List<String> rx(List<String> in) {
return in;
}
}
As you can see by the endpoint annotation, I'm defining an encoder and decoder.
Here's the code for that.
public static class ListStringEncoder implements Encoder.Text<List<String>>
{
@Override
public void init(EndpointConfig endpointConfig) {
}
@Override
public void destroy() {
}
@Override
public String encode(List<String> list) throws EncodeException {
return list.toString();
}
}
public static class ListStringDecoder implements Decoder.Text<List<String>>
{
@Override
public void init(EndpointConfig endpointConfig) {
}
@Override
public void destroy() {
}
@Override
public List<String> decode(String data) throws DecodeException {
List<String> tmp = new ArrayList<String>();
for (String str : data.substring(1, data.length() -
1).split(",")) {
tmp.add(str);
}
return tmp;
}
@Override
public boolean willDecode(String s) {
return s.startsWith("[") && s.endsWith("]");
}
}
Now when I run this, I get the following exception as Tomcat starts up.
16-Oct-2013 11:29:40.311 SEVERE [localhost-startStop-1]
org.apache.catalina.core.StandardContext.listenerStart Exception sending
context initialized event to listener instance of class
org.apache.tomcat.websocket.pojo.TesterUtil$ServerConfigListener
java.lang.NullPointerException
at org.apache.tomcat.websocket.Util$DecoderMatch.<init>(Util.java:428)
at
org.apache.tomcat.websocket.pojo.PojoMethodMapping$MessageHandlerInfo.<init>(PojoMethodMapping.java:396)
at
org.apache.tomcat.websocket.pojo.PojoMethodMapping.<init>(PojoMethodMapping.java:114)
at
org.apache.tomcat.websocket.server.WsServerContainer.addEndpoint(WsServerContainer.java:194)
at
org.apache.tomcat.websocket.pojo.TesterUtil$ServerConfigListener.contextInitialized(TesterUtil.java:45)
at
org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4830)
at
org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5276)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1390)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)
If I change my encoder & decoder to use "List" rather than "List<String>"
everything works fine.
Any thoughts on what's going on here?
Thanks
Dan
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