使用JNI在.jar中查找Java类

Question

我正在编写一个程序,我使用JNI从C++代码调用Java函数.如果我.class直接使用文件,我的程序运行正常,但是当我将它添加到jar文件FindClass失败时.例如,这很好

    std::string stdOpt = "-Djava.class.path=<path_to_jar>/dependency.jar;<path_to_class>";

    boost::scoped_array<char> opt(new char[stdOpt.size() + 1]);
    std::copy(stdOpt.begin(), stdOpt.end(), opt.get());
    opt[stdOpt.size()] = '\0';
    options[0].optionString = opt.get();

    JavaVMInitArgs vm_args;
    memset(&vm_args, 0, sizeof(vm_args));
    vm_args.version = JNI_VERSION_1_6;
    vm_args.nOptions = 1;
    vm_args.options = options;
    long status = JNI_CreateJavaVM(&m_pJavaVirtualMachine, (void**)&m_pJavaEnvironment, &vm_args);
    if (status != JNI_OK)
        throw std::logic_error("Cannot start Java Virtual Machine");

    m_class = m_pJavaEnvironment->FindClass("MyClass");
    if(m_class == 0)
        throw std::logic_error("Cannot find Java class");

但是这个失败了

    std::string stdOpt = "-Djava.class.path=<path_to_jar>/dependency.jar;<path_to_jar>/myjar.jar";

    boost::scoped_array<char> opt(new char[stdOpt.size() + 1]);
    std::copy(stdOpt.begin(), stdOpt.end(), opt.get());
    opt[stdOpt.size()] = '\0';
    options[0].optionString = opt.get();

    JavaVMInitArgs vm_args;
    memset(&vm_args, 0, sizeof(vm_args));
    vm_args.version = JNI_VERSION_1_6;
    vm_args.nOptions = 1;
    vm_args.options = options;
    long status = JNI_CreateJavaVM(&m_pJavaVirtualMachine, (void**)&m_pJavaEnvironment, &vm_args);
    if (status != JNI_OK)
        throw std::logic_error("Cannot start Java Virtual Machine");

    m_class = m_pJavaEnvironment->FindClass("MyClass");    //m_class=NULL
    if(m_class == 0)
        throw std::logic_error("Cannot find Java class");  //throwing exception 

当我想要从中获取Java类时,我应该做些什么.jar？怎么了？有任何想法吗？

Answer 1

如果您的类在一个包中,请在调用FindClass时包含该包,而不是类路径.

 m_class = m_pJavaEnvironment->FindClass( "com/mycompany/mypackage/MyClass" );

Answer 2

事实证明，问题不在代码中。代码没问题。问题出在制作.jar文件时。我正在使用 Visual Studio 来自动编译.java和.class添加已添加到项目的预构建事件的文件.class。.jar所以在制作.jar文件之前我应该​​像这样指定当前目录

cd "<_directory_where_.class_file_is_ located>"

jar cf myjar.jar MyClass.class

否则，将其绝对路径的文件夹MyClass.class添加到文件中并失败。.jarFindClass()