java.lang.LinkageError: loader constraint violation: when resolving method "org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor

Question

A JSF web application tries to retrieve resource from a Java EE web service. The JSF web app works fine. Since I added the Http client source to retrive web service resources the JBoss instance claims about:

15:29:47,689 SEVERE [javax.enterprise.resource.webcontainer.jsf.application] (http--0.0.0.0-443-1) Error Rendering View[/index.xhtml]: javax.el.ELException: /surfaceParts/sideBarLeft.xhtml @14,79 value="#{categories.cats}": java.lang.LinkageError: loader constraint violation: when resolving method "org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.<init>(Lorg/apache/http/client/HttpClient;Lorg/apache/http/protocol/HttpContext;)V" the class loader (instance of org/jboss/modules/ModuleClassLoader) of the current class, at/fhj/ase/ssl/SSLClientHelper, and the class loader (instance of org/jboss/modules/ModuleClassLoader) for resolved class, org/jboss/resteasy/client/core/executors/ApacheHttpClient4Executor, have different Class objects for the type xecutors.ApacheHttpClient4Executor.<init>(Lorg/apache/http/client/HttpClient;Lorg/apache/http/protocol/HttpContext;)V used in the signature
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:114) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIData.getValue(UIData.java:731) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIData.getDataModel(UIData.java:1798) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIData.setRowIndexWithoutRowStatePreserved(UIData.java:484) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIData.setRowIndex(UIData.java:473) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at com.sun.faces.renderkit.html_basic.TableRenderer.encodeBegin(TableRenderer.java:81) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:820) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIData.encodeBegin(UIData.java:1118) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1777) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:402) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:125) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:489) [jbossweb-7.0.13.Final.jar:]
    at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.13.Final.jar:]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.13.Final.jar:]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
    at java.lang.Thread.run(Unknown Source) [rt.jar:1.7.0_25]
Caused by: java.lang.LinkageError: loader constraint violation: when resolving method "org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.<init>(Lorg/apache/http/client/HttpClient;Lorg/apache/http/protocol/HttpContext;)V" the class loader (instance of org/jboss/modules/ModuleClassLoader) of the current class, at/fhj/ase/ssl/SSLClientHelper, and the class loader (instance of org/jboss/modules/ModuleClassLoader) for resolved class, org/jboss/resteasy/client/core/executors/ApacheHttpClient4Executor, have different Class objects for the type xecutors.ApacheHttpClient4Executor.<init>(Lorg/apache/http/client/HttpClient;Lorg/apache/http/protocol/HttpContext;)V used in the signature
    at at.fhj.ase.ssl.SSLClientHelper.getSSLClientRequest(SSLClientHelper.java:71) [classes:]
    at at.fhj.ase.beans.Categories.getCats(Categories.java:39) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_25]
    at java.lang.reflect.Method.invoke(Unknown Source) [rt.jar:1.7.0_25]
    at javax.el.BeanELResolver.getValue(BeanELResolver.java:302) [jboss-el-api_2.2_spec-1.0.0.Final.jar:1.0.0.Final]
    at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at org.apache.el.parser.AstValue.getValue(AstValue.java:169) [jbossweb-7.0.13.Final.jar:]
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:189) [jbossweb-7.0.13.Final.jar:]
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109) [jsf-impl-2.1.7-jbossorg-2.jar:]
    ... 36 more

I'm pretty sure that the HttpClient source is fine, since it's the same what is used at the web service side for JUnit tests.

ProjectSetup: The web service is deployed on JBoss AS7.1 (works fine so far) The JSF web client is deployed on the same JBoss instance. Both are started via Eclipse. The Deployment assembly for of the JSF web client looks like:

I assume that the linkage error is caused by the external (BuildPath & DeploymentAssembly) added apache http client library. But how do I resolve this?

Please tell me if you need further details. I am very grateful for any help!

Answer 1

The reason why you are seeing the error is because RestEasy has a dependency on httpclient jars which is provided as a jboss module. The version you provided is conflicting with the one provided by JBoss .

Why do you need to package the HTTPClient jars with your web app? Is it for some rest client call? In that case you should use RestEasy which is the default JAX-RS implementation on JBoss AS7. It will be a better framework to use for that purpose.

Your other option is to add a dependency on the org.apache.httpcomponents module in your WEB-INF\jboss-deployment-structure.xml and remove the http-client jars from WEB-INF\lib.