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2017/12/07

[Java] ClassCastException : cannot cast javax.jms.Message to javax.jms.TextMessage

Problem
I get ClassCastException when I read IBM MQ queue message by Java.
The code snippet looks like: 
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package com.xxx.mql.service;

import java.io.IOException;
import java.util.Enumeration;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Queue;
import javax.jms.QueueBrowser;
import javax.jms.Session;
import javax.jms.TextMessage;

import org.apache.commons.lang.StringUtils;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.google.common.base.Strings;
import com.ibm.mq.jms.MQQueueConnection;
import com.ibm.mq.jms.MQQueueConnectionFactory;
import com.ibm.mq.jms.MQQueueReceiver;
import com.ibm.mq.jms.MQQueueSession;
import com.tdcc.common.type.MQInfoEnum;
import com.tdcc.mql.utils.MqlUtils;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class TestMQService {

    private static TestMQService mqServuce;

    private static String mqHost = MQInfoEnum.MQ_HOST.getValue();
    private static String mqChannel = MQInfoEnum.MQ_CHANNEL.getValue();
    private static String mqUser = MQInfoEnum.MQ_USER.getValue();
    private static String mqPwd = "";
    private static String mqQueueMgr = MQInfoEnum.MQ_QUEUEMGR.getValue();

    public static TestMQService getInstance() {
        if (mqServuce == null) {
            mqServuce = new TestMQService();
            return mqServuce;
        } else {
            return mqServuce;
        }
    }

    /**
     * 透過 JMS 去取得 queue message.
     * 
     * @param queueName
     * @return
     * @throws JMSException
     */
    public String readMessageByJMS(String queueName) throws JMSException {
        MQQueueConnectionFactory connFactory = new MQQueueConnectionFactory();
        MQQueueReceiver receiver = null;
        MQQueueSession session = null;
        MQQueueConnection connection = null;
        String message = "";
        try {
            // Config
            connFactory.setHostName(mqHost);
            connFactory.setPort(1414);
            connFactory.setTransportType(1);
            connFactory.setQueueManager(mqQueueMgr);
            connFactory.setChannel(mqChannel);

            connection = (MQQueueConnection) connFactory.createQueueConnection();
            session = (MQQueueSession) connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            Queue queue = session.createQueue(queueName);
            receiver = (MQQueueReceiver) session.createReceiver(queue);

            connection.start();

            if (receiver != null) {
                Message msg = receiver.receiveNoWait();
                if (msg == null) {
                    message = "";
                } else {
                    TextMessage textMsg = (TextMessage) msg;
                    message = StringUtils.defaultIfBlank(textMsg.getText(), "");
                }
            }

        } catch (JMSException e) {
            log.error(MqlUtils.toStackTrace(e));
        } finally {
            if (receiver != null) {
                receiver.close();
            }
            if (session != null) {
                session.close();
            }
            if (connection != null) {
                connection.close();
            }
        }
        log.info("[readMessageByJMS] message = " + message);
        return message;
    }
}


How-to
According to original requirement, the queue message should be text format. 

 Different content format will use different interface:
But actually it may has non-text format in IBM MQ, so I need to check its class type before do cast. 
The updated code snippet are as bellows: 
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package com.xxx.mql.service;

import java.io.IOException;
import java.util.Enumeration;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Queue;
import javax.jms.QueueBrowser;
import javax.jms.Session;
import javax.jms.TextMessage;

import org.apache.commons.lang.StringUtils;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.google.common.base.Strings;
import com.ibm.mq.jms.MQQueueConnection;
import com.ibm.mq.jms.MQQueueConnectionFactory;
import com.ibm.mq.jms.MQQueueReceiver;
import com.ibm.mq.jms.MQQueueSession;
import com.tdcc.common.type.MQInfoEnum;
import com.tdcc.mql.utils.MqlUtils;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class TestMQService {

    private static TestMQService mqServuce;

    private static String mqHost = MQInfoEnum.MQ_HOST.getValue();
    private static String mqChannel = MQInfoEnum.MQ_CHANNEL.getValue();
    private static String mqUser = MQInfoEnum.MQ_USER.getValue();
    private static String mqPwd = "";
    private static String mqQueueMgr = MQInfoEnum.MQ_QUEUEMGR.getValue();

    public static TestMQService getInstance() {
        if (mqServuce == null) {
            mqServuce = new TestMQService();
            return mqServuce;
        } else {
            return mqServuce;
        }
    }

    /**
     * 透過 JMS 去取得 queue message.
     * 
     * @param queueName
     * @return
     * @throws JMSException
     */
    public String readMessageByJMS(String queueName) throws JMSException {
        MQQueueConnectionFactory connFactory = new MQQueueConnectionFactory();
        MQQueueReceiver receiver = null;
        MQQueueSession session = null;
        MQQueueConnection connection = null;
        String message = "";
        try {
            // Config
            connFactory.setHostName(mqHost);
            connFactory.setPort(1414);
            connFactory.setTransportType(1);
            connFactory.setQueueManager(mqQueueMgr);
            connFactory.setChannel(mqChannel);

            connection = (MQQueueConnection) connFactory.createQueueConnection();
            session = (MQQueueSession) connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            Queue queue = session.createQueue(queueName);
            receiver = (MQQueueReceiver) session.createReceiver(queue);

            connection.start();

            if (receiver != null) {
                Message msg = receiver.receiveNoWait();
                if (msg == null) {
                    message = "";
                } else {
                    if (msg instanceof TextMessage) {
                        TextMessage textMsg = (TextMessage) msg;
                        message = StringUtils.defaultIfBlank(textMsg.getText(), "");
                    } else {
                        String error = "*****不是文字訊息，跳過此筆訊息，class type = " + msg.getClass().toString();
                        log.error(error);
                    }
                }
            }

        } catch (JMSException e) {
            log.error(MqlUtils.toStackTrace(e));
        } finally {
            if (receiver != null) {
                receiver.close();
            }
            if (session != null) {
                session.close();
            }
            if (connection != null) {
                connection.close();
            }
        }
        log.info("[readMessageByJMS] message = " + message);
        return message;
    }
}


Reference
[1] https://docs.oracle.com/javaee/6/api/javax/jms/Message.html
Posted by Albert Kuo at 8:00 AM
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