在运行时将包含 java 源的文件夹添加到类路径

发布于 2024-08-31 06:08:17 字数 494 浏览 1 评论 0原文

是否可以添加包含 java 源代码的文件夹作为类路径元素。我尝试了一些方法，似乎类加载器没有拾取 java 源文件？我的尝试之一如下所示......

File uncompressedSrc = new File("uncompressed" + File.separator + "src" + File.separator);
URL uncompressedSrcURL = null;
try {
    uncompressedSrcURL = new URL("file://"
        + uncompressedSrc.getAbsolutePath());
} catch (MalformedURLException e) {
    e.printStackTrace();
}
URL elements[] = { uncompressedSrcURL };
new URLClassLoader(elements, ClassLoader.getSystemClassLoader());

原文

Is it possible to add a folder which contains java source code as a classpath element. I have tried a few things and it seems that the classloadr is not picking up java soruce files? One of my attempts is shown below....

File uncompressedSrc = new File("uncompressed" + File.separator + "src" + File.separator);
URL uncompressedSrcURL = null;
try {
    uncompressedSrcURL = new URL("file://"
        + uncompressedSrc.getAbsolutePath());
} catch (MalformedURLException e) {
    e.printStackTrace();
}
URL elements[] = { uncompressedSrcURL };
new URLClassLoader(elements, ClassLoader.getSystemClassLoader());

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半葬歌 2024-09-07 06:08:17

我找到了解决问题的方法...我使用了以下肮脏的“hack”将文件夹添加到类路径中...

public static void addUrl(URL u) {
    URLClassLoader sysloader = (URLClassLoader) ClassLoader
            .getSystemClassLoader();
    Class<URLClassLoader> sysclass = URLClassLoader.class;

    try {
        Method method = sysclass.getDeclaredMethod("addURL", parameters);
        method.setAccessible(true);
        method.invoke(sysloader, new Object[] { u });
    } catch (Throwable t) {
        t.printStackTrace();
        try {
            throw new IOException(
                    "Error, could not add URL to system classloader");
        } catch (IOException e) {
            logger.log(Level.SEVERE, e.getMessage());
        }
    }
}

I have found a solution to my problem... I used the following dirty "hack" to add a folder to class path...

public static void addUrl(URL u) {
    URLClassLoader sysloader = (URLClassLoader) ClassLoader
            .getSystemClassLoader();
    Class<URLClassLoader> sysclass = URLClassLoader.class;

    try {
        Method method = sysclass.getDeclaredMethod("addURL", parameters);
        method.setAccessible(true);
        method.invoke(sysloader, new Object[] { u });
    } catch (Throwable t) {
        t.printStackTrace();
        try {
            throw new IOException(
                    "Error, could not add URL to system classloader");
        } catch (IOException e) {
            logger.log(Level.SEVERE, e.getMessage());
        }
    }
}

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夏末 2024-09-07 06:08:17

Java 源代码不是 JVM 本身可以处理的。类加载器只能加载已编译的类文件。因此，您只能将 JAR 文件或 CLASS 文件的内容添加到类路径中。

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卖梦商人 2024-09-07 06:08:17

对不起。我快速浏览了你的问题。

正如@Daniel所说，JVM无法读取.java文件，只能读取.class文件。

java 文件可以编译成类文件并以编程方式加载到 JVM 中，如下所述：使用 Java 以编程方式编译和执行

关键成分是以下

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager filemanager = compiler.getStandardFileManager( null, null, null );

try {
    Iterable compilationUnits = filemanager.getJavaFileObjects( file );
    compiler.getTask( null, filemanager, null, null, null, compilationUnits ).call();

    filemanager.close();
} catch ( IOException e ) {
    e.printStackTrace();
}

希望有帮助！

Sorry. I skimmed through your question way to fast.

As @Daniel says, the JVM can not read .java files, only .class files.

The java-files can be compiled into class-files and loaded in the JVM programatically as described here: Programmatically Compile and Execute with Java

The key ingredient is the following

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager filemanager = compiler.getStandardFileManager( null, null, null );

try {
    Iterable compilationUnits = filemanager.getJavaFileObjects( file );
    compiler.getTask( null, filemanager, null, null, null, compilationUnits ).call();

    filemanager.close();
} catch ( IOException e ) {
    e.printStackTrace();
}

Hope that helps!

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