我有一个 panelAdmin 页面，当我单击 adminList 时，我转发参数
<h:commandLink value="Admini" action="#{userMB.adminList()}">
<f:param name="userId" value="#{loginMB.user.id}" />
</h:commandLink>
用户MB方法
public String adminList() {
return "adminList";
}
和面孔配置：
<navigation-rule>
<from-view-id>/adminPanel.xhtml</from-view-id>
<navigation-case>
<from-outcome>adminList</from-outcome>
<to-view-id>/adminList.xhtml</to-view-id>
</navigation-case>
我的管理列表页面：
<?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:ui="http://java.sun.com/jsf/facelets"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui"
xmlns:c="http://java.sun.com/jsp/jstl/core">
<h:head>
<title>Lista adminow</title>
</h:head>
<h:body>
<h3>Zalogwano jako: #{loginMB.user.firstName} #{loginMB.user.firstName}</h3>
<h3>Lista administratorów</h3>
<f:view>
<h:form>
<p:dataTable value="#{userMB.allAdmins}" var="admin" widgetVar="customerTable">
<p:column headerText="Imie">
#{admin.firstName}
</p:column>
<p:column headerText="Nazwisko">
#{admin.lastName}
</p:column>
<p:column headerText="Pesel">
#{admin.personalId}
</p:column>
<p:column headerText="Edytuj">
<h:commandLink value="Edytuj" action="#{userMB.editStart()}">
<f:setPropertyActionListener target="#{userMB.user}" value="#{admin}" />
</h:commandLink>
</p:column>
<p:column headerText="Usun">
<h:commandLink value="Usun" action="#{userMB.deleteUser()}">
<f:setPropertyActionListener target="#{userMB.user}" value="#{admin}" />
</h:commandLink>
</p:column>
</p:dataTable>
<h:commandButton value="add" action="#{userMB.createStart()}"/>
<h:commandButton value="back" action="/adminPanel.xhtml"/>
</h:form>
</f:view>
</h:body>
</html>
当我单击添加按钮或后退按钮时出现错误：HTTP Status 500
type Exception report
message
descriptionThe server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException
root cause
java.lang.NullPointerException
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.1.2.2 logs.
在 glassfish 服务器日志中：
WARNING: StandardWrapperValve[Faces Servlet]: PWC1406: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
at pl.ePrzychodnia.mb.UserMB.getAllAdmins(UserMB.java:51)
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:601)
at javax.el.BeanELResolver.getValue(BeanELResolver.java:363)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at com.sun.el.parser.AstValue.getValue(AstValue.java:138)
at com.sun.el.parser.AstValue.getValue(AstValue.java:183)
at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:224)
at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182)
at javax.faces.component.UIData.getValue(UIData.java:731)
at org.primefaces.component.datatable.DataTable.getValue(DataTable.java:729)
at org.primefaces.component.api.UIData.getDataModel(UIData.java:575)
at org.primefaces.component.api.UIData.setRowModel(UIData.java:405)
at org.primefaces.component.api.UIData.setRowIndex(UIData.java:397)
at org.primefaces.component.api.UIData.processPhase(UIData.java:254)
at org.primefaces.component.api.UIData.processDecodes(UIData.java:223)
at javax.faces.component.UIForm.processDecodes(UIForm.java:225)
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176)
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176)
at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:933)
at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78)
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:722)
用户MB
@ManagedBean
@RequestScoped
public class UserMB {
@EJB
private UserFacadeLocal userFacade;
private User user;
public List<User> getAllAdmins() {
return userFacade.findAllAdmins();
}
用户外观
@Stateless
public class UserFacade implements UserFacadeLocal {
@PersistenceContext
private EntityManager em;
@EJB
private UserDao userDao;
@Override
public List<User> findAllAdmins() {
FacesContext context = FacesContext.getCurrentInstance();
Map requestParameterMap = (Map) context.getExternalContext().getRequestParameterMap();
String paramId = requestParameterMap.get("userId").toString();
Integer userId = Integer.parseInt(paramId);
Query q = em.createQuery("SELECT u FROM User u where u.role = 'admin' and u.id <> :id");
q.setParameter("id", userId);
List<User> users = q.getResultList();
return users;
}