Question

首先，我很抱歉我的英语不好。当我从KisiDao类创建一个对象，我尝试使用它是我得到错误“NullPointerException”。我在这个网站上搜索了这个错误，但我找不到。

Kisi.java

package model;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Kisi implements Serializable {

    private static final long serialVersionUID = -1527914551724665414L;

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Integer id;

    private String adi;

    private String soyadi;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getAdi() {
        return adi;
    }

    public void setAdi(String adi) {
        this.adi = adi;
    }

    public String getSoyadi() {
        return soyadi;
    }

    public void setSoyadi(String soyadi) {
        this.soyadi = soyadi;
    }



}

KisiDao.java

package dao;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import model.Kisi;

@Stateless
public class KisiDao {


    @PersistenceContext
    private EntityManager entityManager;

    public Kisi KisiKaydet(Kisi kisi)
    {
        entityManager.persist(kisi);
        return kisi;
    }
}

KisiService.java

package service;

import java.io.Serializable;

import javax.annotation.PostConstruct;
import javax.ejb.EJB;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

import model.Kisi;
import dao.KisiDao;

@ManagedBean(name="kisiService")
@ViewScoped
public class KisiService implements Serializable{

    private static final long serialVersionUID = -9027472804586886314L;

    @EJB
    private KisiDao kisiDao;

    private Kisi kisi = new Kisi();

    public void KisiKaydet()
    {
        kisiDao.KisiKaydet(kisi); //NullPointerException here
    }
    public Kisi getKisi() {
        return kisi;
    }

    public void setKisi(Kisi kisi) {
        this.kisi = kisi;
    }

}

这是控制台日志。

WARNING: java.lang.NullPointerException
javax.el.ELException: java.lang.NullPointerException
    at org.apache.el.parser.AstValue.invoke(AstValue.java:258)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:277)
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:149)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:818)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    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:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
    at service.KisiService.KisiKaydet(KisiService.java:25)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:245)
    ... 33 more

Answer 1

看起来你正在使用Tomcat。默认情况下，Tomcat不支持EJB，这就是为什么它是null。如果您正在寻找具有EJB支持的轻量级服务器，请检查WebSphere Liberty https://developer.ibm.com/wasdev/

注入EJB注释时出现NullPointerException错误

1 个答案: