使用FileInputStream在Resources中加载文件 [英] Load a file in Resources with FileInputStream

问题描述

我知道在资源中打开文件的安全方法是：

I know the safe way to open a file in the resources is:

  InputStream is = this.getClass().getResourceAsStream("/path/in/jar/file.name");  

现在问题是我的文件是Weka Wrapper包中的决策者的模型和
Decider类只有一个方法：

now the problem is that my file is a model for a decider in the Weka Wrapper package and the Decider class has only a method:

  public void load(File file) throws Exception 

load获取文件并将其作为FileInputStream打开。你看到了解决方法吗？我真的希望
喜欢将模型运送到资源中。我正在考虑创建一个临时文件，在临时文件中写入模型的内容，然后将临时文件传递给Weka，但它太脏了。
其他选项？

load takes the file and opens it as a FileInputStream. Do you see a workaround? I really would like to ship the model putting it in the resources. I was thinking to create a temporary file, write the content of the model in the temp file and then pass the temporary file to Weka, but it is so dirty.. other options?

推荐答案

我看到2个解决方案：

解决方案1

将类路径资源读取到临时文件并在调用 load（文件）后删除它

Read the classpath ressource to a temp file and delete it after you called load(File)

InputStream cpResource = this.getClass().getClassLoader().getResourceAsStream("file.name");
File tmpFile = File.createTempFile("file", "temp");
FileUtils.copyInputStreamToFile(cpResource, tmpFile); // FileUtils from apache-io
try {
    decider.load(tmpFile);
} finally {
    tmpFile.delete();
}

解决方案2

如果加载资源的ClassLoader是URLClassLoader，您可以尝试查找绝对文件名。但是，只有当您想要的资源作为文件系统上的文件存在时，此才有效。如果文件包含在jar中，它就不起作用。

If the ClassLoader that loads the resource is a URLClassLoader you can try to find the absolute file name. But this only works if the resource you want exists as a file on the filesystem. It doesn't work if the file is contained in a jar.

ClassLoader classLoader = this.getClass().getClassLoader();
if(classLoader instanceof URLClassLoader){
    URLClassLoader urlClassLoader = URLClassLoader.class.cast(classLoader);
    URL resourceUrl = urlClassLoader.findResource("file.name");

    if("file".equals(resourceUrl.getProtocol())){
        URI uri = resourceUrl.toURI();
        File file = new File(uri);
        decider.load(file);
    }
}

我建议写一个试用的实用工具类通过类加载器找到绝对文件，或者如果它不能以这种方式获取它，则使用临时文件方法作为后备。

I would suggest to write a utility class that tries to find the absolute file through the class loader or if it can't get it this way uses the temp file approach as fallback.

或者以更面向对象的方式：

Or in a more object-oriented way:

    public class FileResourceTest {

    public static void main(String[] args) throws IOException {
        File resourceAsFile = getResourceAsFile("file.name");
        System.out.println(resourceAsFile);
    }

    private static File getResourceAsFile(String resource) throws IOException {
        ClassLoader cl = FileResourceTest.class.getClassLoader();
        File file = null;
        FileResource fileResource = new URLClassLoaderFileResource(cl, resource);
        try {
            file = fileResource.getFile();
        } catch (IOException e) {
            fileResource = new ClasspathResourceFileResource(cl, resource);
            file = fileResource.getFile();
        }
        return file;
    }

    public static interface FileResource {

        public File getFile() throws IOException;

    }

    public static class ClasspathResourceFileResource implements FileResource {

        private ClassLoader cl;
        private String resource;

        public ClasspathResourceFileResource(ClassLoader cl, String resource) {
            this.cl = cl;
            this.resource = resource;
        }

        public File getFile() throws IOException {
            InputStream cpResource = cl.getResourceAsStream(resource);
            File tmpFile = File.createTempFile("file", "temp");
            FileUtils.copyInputStreamToFile(cpResource, tmpFile);
            tmpFile.deleteOnExit();
            return tmpFile;
        }

    }

    public static class URLClassLoaderFileResource implements FileResource {

        private ClassLoader cl;
        private String resource;

        public URLClassLoaderFileResource(ClassLoader cl, String resourcePath) {
            this.cl = cl;
            this.resource = resourcePath;
        }

        public File getFile() throws IOException {
            File resourceFile = null;
            if (cl instanceof URLClassLoader) {
                URLClassLoader urlClassLoader = URLClassLoader.class.cast(cl);
                URL resourceUrl = urlClassLoader.findResource(resource);
                if ("file".equals(resourceUrl.getProtocol())) {
                    try {

                        URI uri = resourceUrl.toURI();
                        resourceFile = new File(uri);
                    } catch (URISyntaxException e) {
                        IOException ioException = new IOException(
                                "Unable to get file through class loader: "
                                        + cl);
                        ioException.initCause(e);
                        throw ioException;
                    }

                }
            }
            if (resourceFile == null) {
                throw new IOException(
                        "Unable to get file through class loader: " + cl);
            }
            return resourceFile;
        }

    }
}

你可以还可以使用 commons-vfs 等第三方图书馆允许您引用jar中的文件。例如。 jar：// arch-file-uri [！绝对路径] 。由于commons-vfs指定了自己的 FileObject 代表一个文件，你仍然必须将内容复制到本地 java.io.File 以适应决策者.load（文件） API。

You can also use a thrid party library like commons-vfs that allows you to reference a file within a jar. E.g. jar:// arch-file-uri[! absolute-path]. Since commons-vfs specifies an own FileObject that represents a file you must still copy the content to a local java.io.File to adapt to the Decider.load(File) API.

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