CDI @inject can't instantiate my service

StackOverflow https://stackoverflow.com/questions/20422390

  •  29-08-2022
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Question

i have a problem with my @inject annotation it can't instantiate my service. i follow every tutorial and official document without success. please can you help me to figure out my problem.

my controller: `

@Named
@ManagedBean
@RequestScoped
public class LoginAction {

    private Logger logger = LoggerFactory.getLogger( LoginAction.class );

    @Size(min = 5 , message = "#{msg.auth_txtLog_minLeng}")
    private String txtUserName;
    @Size(min = 5 , message = "#{msg.auth_txtPwd_minLeng}")
    private String txtPassWord;



    @Inject
    private UserService userService;

my service that call my DAO 

  @Named
  public class UserServiceImpl implements UserService {

    @Inject
    UserDao userDao;

i get a nullPointerException:

> ATTENTION: #{loginAction.logIn}: java.lang.NullPointerException
javax.faces.FacesException: #{loginAction.logIn}: java.lang.NullPointerException
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    ... 23 more
Caused by: java.lang.NullPointerException
    at ma.trk.sgpa.controller.LoginAction.logIn(LoginAction.java:35)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    ... 24 more
6 déc. 2013 11:37:43 org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() for servlet [Faces Servlet] in context with path [/sgpa-jsf] threw exception [java.lang.NullPointerException] with root cause
Was it helpful?

Solution

Stacktrace says that you're using Tomcat as indicated by org.apache.tomcat/coyote/catalina.* lines. However, Tomcat does as being a barebones JSP/Servlet container not natively support CDI, it has to be installed separately (like as you did for JSF).

Stacktrace also says that bean isn't managed by @Named but by @ManagedBean as indicated by complete absense of CDI proxy class signature in the root cause. If @Named was really used, you'd have seen an extra line as follows when Weld is used as CDI implementation:

Caused by: java.lang.NullPointerException
    at ma.trk.sgpa.controller.LoginAction.logIn(LoginAction.java:35)
--> at ma.trk.sgpa.controller.LoginAction$Proxy$_$$_WeldClientProxy.logIn(LoginAction$Proxy$_$$_WeldClientProxy.java)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    ...

Also, your comment

still not working. if i remove @ManagedBean my page Xhtml don't know my fields

confirms that CDI isn't properly installed at all. It's also surprising that you didn't explicitly mention anywhere how exactly you installed it because Tomcat+CDI is a special case, which confirms that you actually had no idea what you were doing. Perhaps you just faced a compilation error on @Named and @Inject and you just blindly downloaded/moved/copied random JAR files in a careless attempt to solve those compilation errors without actually reading the documentation of CDI implementation as to configuring Tomcat.

Head to the following answer to learn how to get CDI to work in Tomcat: How to install and use CDI on Tomcat?.

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