问题
I have to get access to a session scoped CDI bean from another request scoped CDI bean. I have got:
- the session scoped CDI bean which keeps a logged in user,
- the request scoped CDI bean which processes some data and needs (for this purpose) of the instance of currently logged in user.
At the moment when I try to get access to the session scoped bean from request scoped bean (through the @Inject annotation) as you see below - I get the NullPointerException exception in this line (which is located in addData method):
String surname=loginController.getCurrentUser().getSurname();
Could you tell me how can I fix this issue?
Of course, If I print for example: #{loginController.currentUser.surname} from any xhtml pages, everything works but I need access from the bean, not from the xhtml page.
This is a part of login page:
<h:form class="form">
<p:growl id="growl" showDetail="false" />
<h:inputText id="username" value="#{userLogin.username}" label="Username" required="true" requiredMessage="Username: This field is required." title="Enter your username." pt:placeholder="Username" />
<h:inputSecret id="password" value="#{userLogin.password}" label="Password" required="true" requiredMessage="Password: This field is required." title="Enter your password." pt:placeholder="Password" />
<p:commandButton value="Login" action="#{loginController.login}" update="growl" styleClass="buttonStyle"/>
</h:form>
This is a session scoped CDI bean:
@Named
@SessionScoped
public class LoginController implements Serializable {
private static final long serialVersionUID = -6322113716363932422L;
public String login(){
if(userService.login(userLogin)){
currentUser=userService.getCurrnetUser(userLogin.getUsername());
return "home?faces-redirect=true";
}
else{
facesContext.addMessage(null, new FacesMessage("Data entered are incorrect"));
return null;
}
}
public String logout(){
currentUser=null;
return "login?faces-redirect=true";
}
public boolean isLoggedIn() {
return currentUser!=null;
}
@Produces
@LoggedIn
public UserAccount getCurrentUser(){
return currentUser;
}
@Inject
private FacesContext facesContext;
@Inject
private UserServiceImpl userService;
@Named
@Produces
@RequestScoped
private UserAccount userLogin=new UserAccount();
private UserAccount currentUser;
}
This is a request scoped CDI bean:
@Named
@RequestScoped
public class DataServiceImpl implements DataService {
@Override
public void addData(String[] data) {
//Proccess some data
String surname=loginController.getCurrentUser().getSurname();
//Proccess some data
}
@Inject
private LoginController loginController;
}
This is a stacktrace:
18:45:08,968 WARNING [javax.enterprise.resource.webcontainer.jsf.lifecycle] (default task-15) #{dataController.send()}: java.lang.NullPointerException: javax.faces.FacesException: #{dataController.send()}: 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:658)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:284)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:263)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:174)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:793)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
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:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
... 34 more
Caused by: java.lang.NullPointerException
at com.system.service.DataServiceImpl.addData(DataServiceImpl.java:24)
at com.system.controller.DataController.send(DataController.java:97)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at javax.el.ELUtil.invokeMethod(ELUtil.java:308)
at javax.el.BeanELResolver.invoke(BeanELResolver.java:415)
at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:256)
at com.sun.el.parser.AstValue.invoke(AstValue.java:285)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:304)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
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:87)
... 35 more
18:45:08,971 SEVERE [javax.enterprise.resource.webcontainer.jsf.context] (default task-15) 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)
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:658)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:284)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:263)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:174)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:793)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at com.system.service.DataServiceImpl.addData(DataServiceImpl.java:24)
at com.system.controller.DataController.send(DataController.java:97)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at javax.el.ELUtil.invokeMethod(ELUtil.java:308)
at javax.el.BeanELResolver.invoke(BeanELResolver.java:415)
at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:256)
at com.sun.el.parser.AstValue.invoke(AstValue.java:285)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:304)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
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:87)
... 35 more
This is another CDI bean in which is located a send method (from which I call to the addData method) which we can see in the stacktrace:
@Named
@ViewScoped
public class DataController implements Serializable {
private static final long serialVersionUID = 1383572529241805730L;
//some methods
public void send(){
if(uploadFile==null){
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, "The file isn't uploaded", "You should upload a file"));
}
else{
//Sending the data to the database...
list=new ArrayList<String>();
//It should be a upload file but for now I add it manually.
try(Stream<String> stream=Files.lines(Paths.get("F:/VirtualBox/Share/capture20110815.binetflow"))) {
list=stream.collect(Collectors.toList());
int start=0;
Pattern pattern=Pattern.compile(",");
dataService=new DataServiceImpl();
for (String s : list) {
if(start!=0){
String[] data=pattern.split(s);
dataService.addData(data);
}
else start++;
}
} catch (IOException e) {
e.printStackTrace();
}
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_INFO, "The data has been added.", ""));
}
}
@Named
@Produces
@RequestScoped
private UserTable userTable=new UserTable();
@Inject
private DataService dataService;
@Inject
private FacesContext facesContext;
@Inject
private Logger log;
private UploadedFile uploadFile;
private List<String> list;
}
回答1:
I found the solution. Step by step what I did:
I deleted the
LoginControllerfrom theDataServiceImplbean and I injected theUserAccountwith@LoggedInannotation to theDataControllerbean:@Named @ViewScoped public class DataController implements Serializable { //other fields and methods @Inject @LoggedIn private UserAccount currentUser; }You can also inject the
LoginControllerto theDataControllerbean instead of theUserAccountbut it isn't recommended. You would better if you inject theUserAccount.I created the
addCurrnetUser()method in theDataServiceImplclass. The parameter of the method is theUserAccountobject:@Named @RequestScoped public class DataServiceImpl implements DataService { @Override public void addCurrentUser(UserAccount currentUser){ this.currentUser=currentUser; } @Override public void addData(String[] data) { //Proccess some data String surname=loginController.getCurrentUser().getSurname(); //Proccess some data } private UserAccount currentUser; }I called
dataService.addCurrentUser(currentUser)insend()method (which is located in theDataControllerbean) before callingdataService.addData().
You can also have a question: why does the injected LoginController returns null in the DataServiceImpl bean and in the DataController bean not? Look at this discussion. You can find a few reason there.
来源：https://stackoverflow.com/questions/36115190/get-access-to-cdi-bean-from-another-cdi-bean