如何从客户端创建远程会话EJB

Question

根据EJB客户端应用程序的Netbeans教程，我似乎无法调用方法：

编译错误：

-do-compile:
    [mkdir] Created dir: /home/thufir/NetBeansProjects/EntAppClient/build/empty
    [mkdir] Created dir: /home/thufir/NetBeansProjects/EntAppClient/build/generated-sources/ap-source-output
    [javac] Compiling 1 source file to /home/thufir/NetBeansProjects/EntAppClient/build/jar
    [javac] /home/thufir/NetBeansProjects/EntAppClient/src/java/entappclient/Main.java:16: error: cannot find symbol
    [javac]         System.err.println("result = " + mySession.getResult());
    [javac]                                                   ^
    [javac]   symbol:   method getResult()
    [javac]   location: variable mySession of type MySessionRemote
    [javac] 1 error
BUILD FAILED

客户端：

package entappclient;
import ejb.MySessionRemote;
import javax.ejb.EJB;
public class Main {
    @EJB
    private static MySessionRemote mySession;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        System.err.println("result = " + mySession.getResult());
    }
}

ejb：

package ejb;
import javax.ejb.Stateless;
@Stateless
public class MySession implements MySessionRemote {
    public String getResult() {
        return "This is My Session Bean";
    }
}

远程接口：

package ejb;
import javax.ejb.Remote;
@Remote
public interface MySessionRemote {
}

现在，如果接口被修改：

package ejb;
import javax.ejb.Remote;
@Remote
public interface MySessionRemote {
    public String getResult();
}

bean现在可以@Override方法：

package ejb;
import javax.ejb.Stateless;
@Stateless
public class MySession implements MySessionRemote {
    @Override
    public String getResult() {
        return "This is My Session Bean";
    }
}

然而，有一个NPE:

-run:
     [java] java.lang.reflect.InvocationTargetException
     [java]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     [java]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
     [java]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
     [java]     at java.lang.reflect.Method.invoke(Method.java:606)
     [java]     at org.glassfish.appclient.client.acc.AppClientContainer.launch(AppClientContainer.java:446)
     [java]     at org.glassfish.appclient.client.AppClientFacade.main(AppClientFacade.java:166)
     [java] Caused by: java.lang.NullPointerException
     [java]     at entappclient.Main.main(Main.java:16)
     [java]     ... 6 more
     [java] Java Result: 1
run:
BUILD SUCCESSFUL
Total time: 18 seconds
thufir@dur:~/NetBeansProjects/EntAppClient$ 

如何正确调用该方法？EJB没有实例化？

Answer 1

我从零开始。我能想到的唯一区别是，我没有制作EJB应用程序，而是为bean制作了一个EJB模块。否则，我想也是一样。

结构：

thufir@dur:~/NetBeansProjects$ 
thufir@dur:~/NetBeansProjects$ tree HelloLibrary/
HelloLibrary/
├── build.xml
├── nbproject
│   ├── build-impl.xml
│   ├── genfiles.properties
│   ├── private
│   │   └── private.properties
│   ├── project.properties
│   └── project.xml
└── src
    └── hello
        └── HelloBeanRemote.java
4 directories, 7 files
thufir@dur:~/NetBeansProjects$ 
thufir@dur:~/NetBeansProjects$ tree HelloEJB/
HelloEJB/
├── build.xml
├── nbproject
│   ├── ant-deploy.xml
│   ├── build-impl.xml
│   ├── genfiles.properties
│   ├── private
│   │   └── private.properties
│   ├── project.properties
│   └── project.xml
└── src
    ├── conf
    │   └── MANIFEST.MF
    └── java
        └── hello
            └── HelloBean.java
6 directories, 9 files
thufir@dur:~/NetBeansProjects$ 
thufir@dur:~/NetBeansProjects$ tree HelloClient/
HelloClient/
├── build.xml
├── nbproject
│   ├── ant-deploy.xml
│   ├── build-impl.xml
│   ├── genfiles.properties
│   ├── private
│   │   └── private.properties
│   ├── project.properties
│   └── project.xml
├── src
│   ├── conf
│   │   ├── application-client.xml
│   │   └── MANIFEST.MF
│   └── java
│       └── helloclient
│           └── Main.java
└── test
7 directories, 10 files
thufir@dur:~/NetBeansProjects$ 
thufir@dur:~/NetBeansProjects$ 

客户端代码：

package helloclient;
import hello.HelloBeanRemote;
import javax.ejb.EJB;
public class Main {
    @EJB
    private static HelloBeanRemote helloBean;
    public static void main(String... args) {
        System.out.println(helloBean.Hi());
    }
}

bean：

package hello;
import javax.ejb.Stateless;
@Stateless
public class HelloBean implements HelloBeanRemote {
    @Override
    public String Hi() {
        return "hello world";
    }
    @Override
    public String Bye() {
        return "goodbye";
    }
}

远程接口：

package hello;
import javax.ejb.Remote;
@Remote
public interface HelloBeanRemote {
    public String Hi();
    public String Bye();
}