Null pointer exception when using interceptor

Question

I'm using interceptors for the first time. I followed the course of A. Goncalves, I tried to implement a simple logger interceptor as follows but I got a NPE. I don't understand what is wrong, please explain to me. I used a Qualifier.

Qualifier implementation

package classes;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Target;
import javax.interceptor.InterceptorBinding;

@InterceptorBinding
@Retention(RUNTIME)
@Target({METHOD,TYPE})
public @interface Loggable {

}

Interceptor implementation

package classes;

import java.util.logging.Logger;
import javax.interceptor.AroundInvoke;
import javax.interceptor.Interceptor;
import javax.interceptor.InvocationContext;

@Loggable
@Interceptor
public class LoggingInterceptor {

    private Logger logger;

    @AroundInvoke
    private Object intercept(InvocationContext ic) throws Exception{
        logger.info("> Entry");
        return ic.proceed();
    }
}

Controller implementation

package classes;

import java.io.Serializable;
import javax.faces.bean.ViewScoped;
import javax.inject.Inject;
import javax.inject.Named;

@Loggable
@ViewScoped
@Named
public class BookService implements Serializable{

    public BookService (){
    }

    @Inject
    @ThirteenDigits
    private NumberGenerator generator;

    @Loggable
    public void somePrintMethod(){
        System.err.println("Hello world");
    }
}

XHTML page implemenation

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:p="http://primefaces.org/ui"
      >
    <h:head>
        <title>Interceptor</title>
    </h:head>
    <h:body>
        <h:form>
            <p:commandButton value="Create" action="#{bookService.somePrintMethod}"/>
        </h:form>
    </h:body>
</html>

Error

Avertissement: #{bookService.somePrintMethod}: java.lang.NullPointerException javax.faces.FacesException:

{bookService.somePrintMethod}: 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:794) at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259) 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:118) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231) at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59) at com.sun.grizzly.ContextTask.run(ContextTask.java:71) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513) at java.lang.Thread.run(Thread.java:745) Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102) at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) ... 31 more Caused by: java.lang.NullPointerException at classes.LoggingInterceptor.intercept(LoggingInterceptor.java:25) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.jboss.weld.interceptor.proxy.SimpleMethodInvocation.invoke(SimpleMethodInvocation.java:30) at org.jboss.weld.interceptor.proxy.SimpleInterceptionChain.invokeNextInterceptor(SimpleInterceptionChain.java:68) at org.jboss.weld.interceptor.proxy.InterceptorMethodHandler.executeInterception(InterceptorMethodHandler.java:112) at org.jboss.weld.interceptor.proxy.InterceptorMethodHandler.invoke(InterceptorMethodHandler.java:88) at org.jboss.weld.bean.proxy.CombinedInterceptorAndDecoratorStackMethodHandler.invoke(CombinedInterceptorAndDecoratorStackMethodHandler.java:53) at classes.BookService$Proxy$_$$WeldSubclass.somePrintMethod(BookService$Proxy$$$_WeldSubclass.java) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at com.sun.el.parser.AstValue.invoke(AstValue.java:254) at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302) at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:39) at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50) at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105) at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88) ... 32 more

Well, the flag of my question as a duplicate pushed me to thing otehrwise. I replaced the code of the `LoggingInterceptor` by the following code and it worked `@Loggable @Interceptor @Getter public class LoggingInterceptor { private static Logger LOGGER; public LoggingInterceptor(){ LOGGER = Logger.getLogger("Some text"); } @AroundInvoke private Object intercept(InvocationContext ic) throws Exception{ LOGGER.info("> Entry"); return ic.proceed(); } }` — ziMtyth, Mar 18 '18 at 08:45
Are you sure the Logger is properly injected in your Interceptor? — sn42, Mar 18 '18 at 08:48
@sn42 short answer: I'm not sure. Long one: I had a problem with inject in my interceptor. In the course it is written `@Inject` before the Logger, using that caused me an error that I couldn't understand. I tried many things to solve it, removing `@Inject` made the code work fine. But I don't understand why!! — ziMtyth, Mar 18 '18 at 08:55
@sn42 when I sue the code of the course `@Loggable @Interceptor public class LoggingInterceptor { @Inject private Logger LOGGER; @AroundInvoke private Object intercept(InvocationContext ic) throws Exception{ LOGGER.info("> Entry"); return ic.proceed(); } }` I get the following error `Grave: Exception while loading the app : WELD-001408 Unsatisfied dependencies for type [Logger] with qualifiers [@Default] at injection point [[field] @Inject private classes.LoggingInterceptor.LOGGER]` — ziMtyth, Mar 18 '18 at 09:04

Null pointer exception when using interceptor

{bookService.somePrintMethod}: java.lang.NullPointerException at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)

0 Answers0