ClassCastException:javax.naming.Reference无法强制转换为javax.jms.ConnectionFactory

Question

我写了一个Java程序来连接到Websphere MQ来发布消息.我在Websphere MQ Explore中创建了JNDI名称空间,连接工厂,目标和队列管理器.当我运行我的程序时,它显示ClassCastException从类型转换string到ConnectionFactory.

这是我的代码.任何人都可以帮助解决此问题.

JNDIUtil.java

package com.tradefinance.jms.util;

//JMS classes
import javax.jms.JMSException;
import javax.jms.ConnectionFactory;
import javax.jms.Destination;

//JNDI classes
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;

//Standard Java classes
import java.util.Hashtable;
import java.util.Properties;

/**
* 
* A wrapper class for JNDI calls
*
*/
public class JNDIUtil
{
    private Context context;

    public JNDIUtil(String icf, String url) throws JMSException, NamingException
    {
        Hashtable environment = new Hashtable();

        environment.put(Context.INITIAL_CONTEXT_FACTORY, icf ); 
        environment.put(Context.PROVIDER_URL, url);

     context= new InitialContext( environment );

    }

    /**
     * @param ObjName Object Name to be retrieved
     * @return Retrieved Object
     * @throws NamingException
     */
    private Object getObjectByName(String ObjName) throws NamingException
    {

        return context.lookup(ObjName);
    }

    /**
     * @param factoryName Factory Name
     * @return ConnectionFactory object
     * @throws NamingException
     */
    public ConnectionFactory getConnectionFactory(String factoryName) throws NamingException
    {
        return (ConnectionFactory) getObjectByName(factoryName);
    }

    /**
     * @param destinationName Destination Name
     * @return ConnectionFactory object
     * @throws NamingException
     */
    public Destination getDestination(String destinationName) throws NamingException
    {
        return (Destination) getObjectByName(destinationName);

    }
}

NewPublisher.java

package com.tradefinance.jms.topics;

//JMS classes
import javax.jms.JMSException;
import javax.jms.ConnectionFactory;
import javax.jms.Connection;
import javax.jms.Session;
import javax.jms.Destination;
import javax.jms.MessageProducer;
import javax.jms.TextMessage;

//JNDI classes
import javax.naming.NamingException;

import com.tradefinance.jms.util.JNDIUtil;

/**
 * A class to demonstrate how to a publish to a topic.
 */
public class NewsPublisher
{

    public static String icf = "com.sun.jndi.fscontext.RefFSContextFactory";
    public static String url = "file:/C:/JNDI-Directory/";

    public static void main(String[] vars) throws JMSException, NamingException
    {

        ConnectionFactory factory = null;
        Connection connection = null;
        Session session = null;
        Destination destination= null; // a destination can be a topic or a queue
        MessageProducer producer= null; 


        try
        {   

            JNDIUtil jndiUtil= new JNDIUtil(icf,url);

            factory= jndiUtil.getConnectionFactory("TestQM1ConnectionFactory");

            connection = factory.createConnection();            
            connection.start();

            // Indicate a non-transactional session 
            boolean transacted = false;
            session = connection.createSession( transacted, Session.AUTO_ACKNOWLEDGE);          

            destination = jndiUtil.getDestination("NewsTopic");

            producer = session.createProducer(destination);

            TextMessage message = session.createTextMessage("No News is Good News!");
            producer.send(message); 

            System.out.println("NewsPublisher: Message Publication Completed");

        }
        finally
        {
            // Always release resources

            if ( producer!= null )
                producer.close();   

            if ( session!= null )
                session.close();

            if ( connection!= null )
                connection.close();

        }    
    }           
}

在这些行上获取错误:

return (ConnectionFactory) getObjectByName(factoryName); 
in JNDIUtil.java

factory= jndiUtil.getConnectionFactory("TestQM1ConnectionFactory");
in NewPublisher.java

Answer 1

您从 jndi 上下文收到的返回内容是一个引用。这是构建连接工厂的方法，我怀疑无法找到负责此操作的类，因为所需的 MQ jar 不在类路径中。错误消息并不直观。

如果做不到这一点，我发现调试 jndi 查找问题的一个好方法是获取上下文并在其上执行 list() ，打印出返回的每个对象的详细信息，这样您就可以清楚目录中到底包含什么内容。