Can I call a webservice from Vaadin

Libran · November 23, 2011, 9:39am

We had developed a restlet based webservice some time back that is deployed on our internal server. Now I amtrying to develop a webapp in Vaadin but want it to access the same webservice for the backend processing. In the production environment I deployed both on my local Tomcat 7.0. But while trying to acces the service Vaadin throws the following Exception :

23 Nov, 2011 2:48:50 PM com.vaadin.Application terminalError
SEVERE: Terminal error:
com.vaadin.event.ListenerMethod$MethodException
Cause: java.lang.NoClassDefFoundError: Lorg/slf4j/Logger;
at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:532)
at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:164)
at com.vaadin.ui.AbstractComponent.fireEvent(AbstractComponent.java:1219)
at com.vaadin.ui.Button.fireClick(Button.java:550)
at com.vaadin.ui.Button.changeVariables(Button.java:217)
at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.changeVariables(AbstractCommunicationManager.java:1445)
at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.handleVariableBurst(AbstractCommunicationManager.java:1393)
at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.handleVariables(AbstractCommunicationManager.java:1312)
at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.doHandleUidlRequest(AbstractCommunicationManager.java:763)
at com.vaadin.terminal.gwt.server.CommunicationManager.handleUidlRequest(CommunicationManager.java:296)
at com.vaadin.terminal.gwt.server.AbstractApplicationServlet.service(AbstractApplicationServlet.java:501)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:185)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:151)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:269)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: Lorg/slf4j/Logger;
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.getDeclaredField(Unknown Source)
at java.io.ObjectStreamClass.getDeclaredSUID(Unknown Source)
at java.io.ObjectStreamClass.access$700(Unknown Source)
at java.io.ObjectStreamClass$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.io.ObjectStreamClass.(Unknown Source)
at java.io.ObjectStreamClass.lookup(Unknown Source)
at java.io.ObjectStreamClass.initNonProxy(Unknown Source)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at org.restlet.representation.ObjectRepresentation.(ObjectRepresentation.java:76)
at org.restlet.engine.converter.DefaultConverter.toObject(DefaultConverter.java:269)
at org.restlet.service.ConverterService.toObject(ConverterService.java:158)
at org.restlet.resource.UniformResource.toObject(UniformResource.java:644)
at org.restlet.resource.ClientResource$1.invoke(ClientResource.java:1661)
at $Proxy10.getUser(Unknown Source)
at com.example.helloappvaadin.HelloappvaadinApplication.authenticateUser(HelloappvaadinApplication.java:234)
at com.example.helloappvaadin.HelloappvaadinApplication.authenticate(HelloappvaadinApplication.java:215)
at com.example.helloappvaadin.HelloappvaadinApplication$1.buttonClick(HelloappvaadinApplication.java:156)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:512)
… 27 more
Caused by: java.lang.ClassNotFoundException: org.slf4j.Logger
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
… 56 more

Help would be appreciated

Charles · November 23, 2011, 10:37am

Hi,

This is not directly a Vaadin problem, but your one stemming from your webservice (i.e. you’d have the same problem if you were accessing the web-service from a small java swing/console program. Looking at the stacktrace, I find this

Caused by: java.lang.NoClassDefFoundError: Lorg/slf4j/Logger;
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.getDeclaredField(Unknown Source)
at java.io.ObjectStreamClass.getDeclaredSUID(Unknown Source)
at java.io.ObjectStreamClass.access$700(Unknown Source)
at java.io.ObjectStreamClass$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.io.ObjectStreamClass.<init>(Unknown Source)
at java.io.ObjectStreamClass.lookup(Unknown Source)
at java.io.ObjectStreamClass.initNonProxy(Unknown Source)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at org.restlet.representation.ObjectRepresentation.<init>(ObjectRepresentation.java:76)
at org.restlet.engine.converter.DefaultConverter.toObject(DefaultConverter.java:269)
at org.restlet.service.ConverterService.toObject(ConverterService.java:158)
at org.restlet.resource.UniformResource.toObject(UniformResource.java:644)
at org.restlet.resource.ClientResource$1.invoke(ClientResource.java:1661)
at $Proxy10.getUser(Unknown Source)
at com.example.helloappvaadin.HelloappvaadinApplication.authenticateUser(HelloappvaadinApplication.java:234

It looks like the that is being “read” from your webservice has a reference/import to SLF4J; you’ll need to addthe SL4J jar(s) into your WEB-INF/lib folder. All objects referred to on by the objects going “over the wire” need to be on the class path of both the web service and the Vaadin web app.

Cheers,

Charles.