访问远程/本地会话Bean

问题描述

| 我正在尝试连接到会话bean。我尝试了很多与Google一起找到的方法，但是由于我的JNDI查找总是返回NULL，所以总是会遇到相同的错误。 这是错误：

java.lang.NullPointerException
at org.apache.jsp.index_jsp._jspService(index_jsp.java:85)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:563)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:399)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:317)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:204)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:311)
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:619)

因此，我可能缺少一些配置，但是我是新手。一点帮助？ 这是我的实体Bean：

 package beans;
 import java.util.HashSet;
 import java.util.Set;
 import javax.persistence.*;
 import org.hibernate.annotations.GenericGenerator;

@Entity
public class Album {

@Id
@Column(name=\"idalbum\")
@GeneratedValue(generator=\"album_idalbum_seq\")
@GenericGenerator(name=\"album_idalbum_seq\",strategy = \"increment\")
private int id;

@Column(name=\"nomealbum\")
private String nome;

@ManyToMany
  @JoinTable(name = \"albumfaixas\",joinColumns = { 
          @JoinColumn(name = \"idalbum\") 
          },inverseJoinColumns = {
          @JoinColumn(name=\"idfaixas\")
          }
  )
private Set<Faixas> faixas = new HashSet<Faixas>();

public Album() {}
//gets and sets
}

我的会话Bean：

 package DAO;
 import org.hibernate.*;
 import sFactory.*;
 import java.util.List;
 import javax.ejb.Stateless;
 import javax.persistence.EntityManager;
 import javax.persistence.PersistenceContext;
 import beans.*;


 @Stateless 

 public class AlbumDAO  implements AlbumRemote { 

 @PersistenceContext 
  private EntityManager entityManager;

public List<Album> listaAlbuns() { ... code ... }
public void createalbum(Album f) { ... code ... }
public void updatealbum(Album f) { ... code ... }
public void deletealbum(Album f) { ... code ... }
 }

我的远程接口：

 package DAO;
 import javax.ejb.Remote;
 import java.util.List;
 import beans.Album;

 @Remote 

 public interface AlbumRemote {

public List<Album> listaAlbuns();
public void createalbum(Album f);
public void updatealbum(Album f);       
public void deletealbum(Album f);
 }

我的本地界面：

 package DAO;
 import javax.ejb.Local;
 import java.util.List;
 import beans.Album;

 @Local

 public interface AlbumLocal {

public List<Album> listaAlbuns();
public void createalbum(Album f);
public void updatealbum(Album f);   
public void deletealbum(Album f);
 }

web.xml中的参考：

   <ejb-ref>
     <ejb-ref-name>ejb/AlbumRemote</ejb-ref-name>
     <ejb-ref-type>Session</ejb-ref-type>
     <home>DAO.AlbumLocal</home>
     <remote>DAO.AlbumRemote</remote>
   </ejb-ref>

我的JSP客户端代码：

Context initCtx = new InitialContext();

Context ctx = (Context) initCtx.lookup(\"java:comp/env\"); 

Object x = ctx.lookup(\"ejb/AlbumRemote\");

AlbumRemote fr = (AlbumRemote)PortableRemoteObject.narrow(x,AlbumRemote.class);

fr.createalbum(fx1);    

我正在使用myeclipse进行开发，并使用Tomcat作为服务器     

解决方法

        您真的很亲密。放入openejb.war文件，此代码应该起作用。 Tomcat本身并不支持EJB，但是可以通过OpenEJB轻松实现。实际上，我们现在将此组合称为Apache TomEE，并且正在Java EE 6 Web Profile对其进行认证的过程中。因此它将在Glassfish，JBoss，Geronimo等行列中。 如果您还没有一个文件，请确保您的应用程序中有一个定义持久性单元的“ 7”文件。