错误 21 错误 LNK2019：未解析的外部符号：.... 函数中引用：....

Question

我尝试创建一个以 .cpp 文件开头的 .h 文件。我很确定标题是正确的，但是当我尝试在我的另一个项目中使用 .cpp 文件的功能时，我遇到了很多链接问题。所以我在这里附上了文件，肯定有人可以给我一些解决方案。检查项目属性的第一个解决方案，properties->linker->additional library，我已经做了。

有 .cpp 文件：

IfacomAmqSender.cpp

---

#include <activemq/library/ActiveMQCPP.h>
#include <decaf/lang/Thread.h>
#include <decaf/lang/Runnable.h>
#include <decaf/util/concurrent/CountDownLatch.h>
#include <decaf/lang/Integer.h>
#include <decaf/lang/Long.h>
#include <decaf/lang/System.h>
#include <activemq/core/ActiveMQConnectionFactory.h>
#include <activemq/util/Config.h>
#include <cms/Connection.h>
#include <cms/Session.h>
#include <cms/TextMessage.h>
#include <cms/BytesMessage.h>
#include <cms/MapMessage.h>
#include <cms/ExceptionListener.h>
#include <cms/MessageListener.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <memory>


using namespace activemq::core;
using namespace decaf::util::concurrent;
using namespace decaf::util;
using namespace decaf::lang;
using namespace cms;
using namespace std;


class IfacomAmqSender : public ExceptionListener{

private:

    CountDownLatch m_latch;
    CountDownLatch m_doneLatch;
    Connection* m_connection;
    Session* m_session;
    Destination* m_destination;
    MessageConsumer* m_consumer;
    MessageProducer* m_producer;
    std::auto_ptr<TextMessage> m_message;
    long m_waitMillis;
    bool m_useTopic;
    bool m_sessionTransacted;
    std::string m_brokerURI;
    std::string m_destName;
    DeliveryMode m_message_delivery_mode;
    int m_message_priority;

private:

    //IfacomAmqSender(const IfacomAmqSender&);
    //IfacomAmqSender& operator=(const IfacomAmqSender&);

public:

   IfacomAmqSender(const std::string& brokerURI, int numMessages, bool useTopic = false, bool sessionTransacted = false, const std::string& destName = "IFACOM-CMS", int waitMillis = 1000) :
        m_latch(1),
        m_doneLatch(numMessages),
        m_connection(NULL),
        m_session(NULL),
        m_destination(NULL),
        m_consumer(NULL),
        m_waitMillis(waitMillis),
        m_useTopic(useTopic),
        m_sessionTransacted(sessionTransacted),
        m_destName(destName),
        m_brokerURI(brokerURI) {
    }

    IfacomAmqSender(const std::string& brokerURI, bool useTopic = false, bool sessionTransacted = false, const std::string& destName = "IFACOM-CMS") :
        m_latch(1),
        m_doneLatch(1),
        m_connection(NULL),
        m_session(NULL),
        m_destination(NULL),
        m_consumer(NULL),
        m_waitMillis(1000),
        m_useTopic(useTopic),
        m_sessionTransacted(sessionTransacted),
        m_destName(destName),
        m_brokerURI(brokerURI) {
    }


    virtual ~IfacomAmqSender() {
        cleanup();
    }

    void close() {
        this->cleanup();
    }

    void waitUntilReady() {
        m_latch.await();
    }

//------ Init connexion ---------------

    void createConnection()
    {
        // Create a ConnectionFactory
        auto_ptr<ConnectionFactory> connectionFactory(ConnectionFactory::createCMSConnectionFactory(m_brokerURI));

        // Create a Connection
        m_connection = connectionFactory->createConnection();
        m_connection->start();
        m_connection->setExceptionListener(this);
    }

    void createSession()
    {
        // Create a Session
        if (this->m_sessionTransacted == true) {
            m_session = m_connection->createSession(Session::SESSION_TRANSACTED);
        } else {
            m_session = m_connection->createSession(Session::AUTO_ACKNOWLEDGE);
        }
    }

    void createDestination()
    {
        // Create the destination (Topic or Queue)
        if (m_useTopic) {
            m_destination = m_session->createTopic(m_destName);
        } else {
            m_destination = m_session->createQueue(m_destName);
        }
    }

    void createProducer()
    {
        m_producer = m_session->createProducer(m_destination);
        m_producer->setDeliveryMode(DeliveryMode::NON_PERSISTENT);
    }

    void initConnection() {

        try {

            createConnection();

            // Create the session
            createSession();

            // Create the destination (Topic or Queue)
            createDestination();

            // Create a MessageProducer from the Session to the Topic or Queue
            createProducer();
            m_producer->setDeliveryMode(DeliveryMode::NON_PERSISTENT);

            // Indicate we are ready for messages.
            m_latch.countDown();

            // Wait while asynchronous messages come in.
            m_doneLatch.await(m_waitMillis);

        } catch (CMSException& e) {
            // Indicate we are ready for messages.
            //latch.countDown();
            e.printStackTrace();
        }
    }


    virtual void sendMessage(string text) {
            try {

        std::auto_ptr<TextMessage> message(m_session->createTextMessage(text));
            // to set a property
            ////message->setIntProperty("Integer", ix);
        m_producer->send(message.get());
        message->setCMSTimestamp(System::currentTimeMillis());

        } catch (CMSException& e) {
            e.printStackTrace();
        }
    }


    // Send a ActiveMQ Message
    virtual void sendMessage(std::auto_ptr<TextMessage> amq_message) {
        try {

            amq_message->setCMSTimestamp(System::currentTimeMillis());
            m_producer->send(amq_message.get());

        } catch (CMSException& e) {
            e.printStackTrace();
        }
    }

//--------------------------------------------------

    // If something bad happens you see it here as this class is also been
    // registered as an ExceptionListener with the connection.
    virtual void onException(const CMSException& ex AMQCPP_UNUSED) {
        printf("CMS Exception occurred.  Shutting down client.\n");
        ex.printStackTrace();
        exit(1);
    }

    // Message Priority (0:Lowest - 9:Highest)
    void setPriority(int priority){m_message_priority = priority;}
    int getPriority(){return m_message_priority;}

    // Message Delivery Mode
    void setDeliveryMode(DeliveryMode delivery_mode){m_message_delivery_mode = delivery_mode;}
    DeliveryMode getDeliveryMode(){return m_message_delivery_mode;}

    Session* getSession()
    {
        return m_session;
    }

private:

    void cleanup() {
        if (m_connection != NULL) {
            try {
                m_connection->close();
            } catch (cms::CMSException& ex) {
                ex.printStackTrace();
            }
        }

        // Destroy resources.
        try {
            delete m_destination;
            m_destination = NULL;
            delete m_consumer;
            m_consumer = NULL;
            delete m_session;
            m_session = NULL;
            delete m_connection;
            m_connection = NULL;
        } catch (CMSException& e) {
            e.printStackTrace();
        }
    }

};

mainwindow.cpp 文件：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "IfacomAmqSender.h"
#include <activemq/library/ActiveMQCPP.h>
#include <decaf/lang/Thread.h>
#include <decaf/lang/Runnable.h>
#include <decaf/util/concurrent/CountDownLatch.h>
#include <decaf/lang/Integer.h>
#include <decaf/lang/Long.h>
#include <decaf/lang/System.h>
#include <activemq/core/ActiveMQConnectionFactory.h>
#include <activemq/util/Config.h>
#include <cms/Connection.h>
#include <cms/Session.h>
#include <cms/TextMessage.h>
#include <cms/BytesMessage.h>
#include <cms/MapMessage.h>
#include <cms/ExceptionListener.h>
#include <cms/MessageListener.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <memory>
#include <qstring.h>
#include <QTextStream>
#include <QMessageBox>


using namespace activemq::core;
using namespace decaf::util::concurrent;
using namespace decaf::util;
using namespace decaf::lang;
using namespace cms;
using namespace std;



MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    activemq::library::ActiveMQCPP::initializeLibrary();
    {


    std::string brokerURI;

        brokerURI = "failover://(tcp://localhost:61613?wireFormat=stomp)";      // localhost

       // brokerURI = "failover://(tcp://localhost:61616)";     // localhost

        // Queue name
    std::string destName = "IFACOM-CMS";

    // Queue or Topic 
    bool useTopics = false;         // true=Topic, false=Queue

    // SESSION_TRANSACTED or AUTO_ACKNOWLEDGE
    bool sessionTransacted = false; // if true, commit all messages

    long long startTime = System::currentTimeMillis();

    // ***** Initialisation  **************************************************************
    IfacomAmqSender IfacomMessageBroker(brokerURI, useTopics, sessionTransacted, destName);
    IfacomMessageBroker.initConnection();

    //****** Send message ******************************************************

    std::string text = "My IFaCOM message";
    // Customized message
    try{
        std::auto_ptr<TextMessage> message(IfacomMessageBroker.getSession()->createTextMessage(text));
        message->setCMSTimestamp(System::currentTimeMillis());
        message->setStringProperty("MyProperty", "test");
        IfacomMessageBroker.sendMessage(message);

    } catch (CMSException& e) {
        e.printStackTrace();
    }

    // Simple text message
    IfacomMessageBroker.sendMessage(text);


    long long endTime = System::currentTimeMillis();
    double totalTime = (double)(endTime - startTime) / 1000.0;

    // Close the connection
    IfacomMessageBroker.close();

    ui->label->setText(QString::fromStdString(text));
    }

    // To Do at the end
    activemq::library::ActiveMQCPP::shutdownLibrary();



}

main.cpp 文件：

#include "ifacomamqsender.h"
#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

有头文件：

IfacomAmqSender.h 文件：

#ifndef _IfacomAmqSender_h
#define _IfacomAmqSender_h
#include <activemq/library/ActiveMQCPP.h>
#include <decaf/lang/Thread.h>
#include <decaf/lang/Runnable.h>
#include <decaf/util/concurrent/CountDownLatch.h>
#include <decaf/lang/Integer.h>
#include <decaf/lang/Long.h>
#include <decaf/lang/System.h>
#include <activemq/core/ActiveMQConnectionFactory.h>
#include <activemq/util/Config.h>
#include <cms/Connection.h>
#include <cms/Session.h>
#include <cms/TextMessage.h>
#include <cms/BytesMessage.h>
#include <cms/MapMessage.h>
#include <cms/ExceptionListener.h>
#include <cms/MessageListener.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <memory>

using namespace activemq::core;
using namespace decaf::util::concurrent;
using namespace decaf::util;
using namespace decaf::lang;
using namespace cms;
using namespace std;

 class IfacomAmqSender{

private:

    CountDownLatch m_latch;
    CountDownLatch m_doneLatch;
    Connection* m_connection;
    Session* m_session;
    Destination* m_destination;
    MessageConsumer* m_consumer;
    MessageProducer* m_producer;
    std::auto_ptr<TextMessage> m_message;
    long m_waitMillis;
    bool m_useTopic;
    bool m_sessionTransacted;
    std::string m_brokerURI;
    std::string m_destName;
    DeliveryMode m_message_delivery_mode;
    int m_message_priority;
    IfacomAmqSender(const IfacomAmqSender&);
    IfacomAmqSender& operator=(const IfacomAmqSender&);



public:

    IfacomAmqSender(const std::string&, int, bool, bool, const std::string&, int);
    IfacomAmqSender(const std::string&, bool, bool, const std::string&);

    virtual ~IfacomAmqSender();
    void close();
    void waitUntilReady();
    void cleanup();

    // KH
    void createConnection();
    void createSession();
    void createDestination();
    void createProducer();
    void initConnection();

    virtual void sendMessage(string);

    // Send a ActiveMQ Message
    virtual void sendMessage(std::auto_ptr<TextMessage>);


//--------------------------------------------------

    // If something bad happens you see it here as this class is also been
    // registered as an ExceptionListener with the connection.
    virtual void onException(const CMSException&) ;

    // Message Priority (0:Lowest - 9:Highest)
    void setPriority(int);
    int getPriority();

    // Message Delivery Mode
    void setDeliveryMode(DeliveryMode);
    DeliveryMode getDeliveryMode();

    Session* getSession();

};
#endif

mainwindow.h 文件：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

错误是：

Error   21  error LNK2019: unresolved external symbol "public: __thiscall IfacomAmqSender::IfacomAmqSender(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,bool,bool,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??0IfacomAmqSender@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@_N10@Z) referenced in function "private: void __thiscall MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked@MainWindow@@AAEXXZ)   C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   22  error LNK2019: unresolved external symbol "public: virtual __thiscall IfacomAmqSender::~IfacomAmqSender(void)" (??1IfacomAmqSender@@UAE@XZ) referenced in function __catch$?on_pushButton_clicked@MainWindow@@AAEXXZ$0  C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   23  error LNK2019: unresolved external symbol "public: void __thiscall IfacomAmqSender::close(void)" (?close@IfacomAmqSender@@QAEXXZ) referenced in function __catch$?on_pushButton_clicked@MainWindow@@AAEXXZ$0    C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   24  error LNK2019: unresolved external symbol "public: void __thiscall IfacomAmqSender::initConnection(void)" (?initConnection@IfacomAmqSender@@QAEXXZ) referenced in function "private: void __thiscall MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked@MainWindow@@AAEXXZ)   C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   25  error LNK2019: unresolved external symbol "public: virtual void __thiscall IfacomAmqSender::sendMessage(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?sendMessage@IfacomAmqSender@@UAEXV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function __catch$?on_pushButton_clicked@MainWindow@@AAEXXZ$0   C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   26  error LNK2019: unresolved external symbol "public: virtual void __thiscall IfacomAmqSender::sendMessage(class std::auto_ptr<class cms::TextMessage>)" (?sendMessage@IfacomAmqSender@@UAEXV?$auto_ptr@VTextMessage@cms@@@std@@@Z) referenced in function "private: void __thiscall MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked@MainWindow@@AAEXXZ)  C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   27  error LNK2019: unresolved external symbol "public: class cms::Session * __thiscall IfacomAmqSender::getSession(void)" (?getSession@IfacomAmqSender@@QAEPAVSession@cms@@XZ) referenced in function "private: void __thiscall MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked@MainWindow@@AAEXXZ)    C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\mainwindow.obj  GUI-CMS
Error   28  error LNK1120: 7 unresolved externals   C:\Users\Marco\Desktop\Activemq\ReleaseVersions\GUI-CMS\debug\\GUI-CMS.exe  GUI-CMS

Answer 1

我不明白你的代码。它有两个不同的类 IfacomAmqSender 定义。第一个是

class IfacomAmqSender : public ExceptionListener{

第二个是

class IfacomAmqSender{

我认为错误的原因是这些类 IfacomAmqSender 的重复

Answer 2

您的 IfacomAmqSender 构造函数声明如下：

IfacomAmqSender(const std::string&, int, bool, bool, const std::string&, int);

实现头如下：

IfacomAmqSender(const std::string& brokerURI, int numMessages, bool useTopic = false, bool sessionTransacted = false, const std::string& destName = "IFACOM-CMS", int waitMillis = 1000);

所以你的实现声明了标准参数值，而声明没有。因此，在任何调用的地方，函数是否可以采用标准参数都是非常随机的。要么删除所有标准参数，要么确保在声明和实现中在任何地方声明它们都是相同的。 （我的 C++ 有点生锈，我认为它的主要位置是 .h 文件中的声明）。

哦，见鬼，是的：见另一个答案。该实现有另一个类头文件。因此，您实际上是在声明两个具有相同名称的类。 CPP 文件中通常没有任何class X : public Y 声明。