我想从我的罐子里像这样读一个资源:

File file;
file = new File(getClass().getResource("/file.txt").toURI());
BufferedReader reader = new BufferedReader(new FileReader(file));

//Read the file

当在Eclipse中运行它时,它工作得很好,但如果我将它导出到一个jar,然后运行它,会有一个IllegalArgumentException:

Exception in thread "Thread-2"
java.lang.IllegalArgumentException: URI is not hierarchical

我真的不知道为什么,但通过一些测试,我发现如果我改变了

file = new File(getClass().getResource("/file.txt").toURI());

to

file = new File(getClass().getResource("/folder/file.txt").toURI());

然后它反过来工作(它在jar中工作,但在eclipse中不工作)。

我正在使用Eclipse,文件所在的文件夹位于类文件夹中。


当前回答

这段代码在Eclipse和Exported Runnable JAR中都可以工作

private String writeResourceToFile(String resourceName) throws IOException {
    File outFile = new File(certPath + File.separator + resourceName);

    if (outFile.isFile())
        return outFile.getAbsolutePath();
    
    InputStream resourceStream = null;
    
    // Java: In caso di JAR dentro il JAR applicativo 
    URLClassLoader urlClassLoader = (URLClassLoader)Cypher.class.getClassLoader();
    URL url = urlClassLoader.findResource(resourceName);
    if (url != null) {
        URLConnection conn = url.openConnection();
        if (conn != null) {
            resourceStream = conn.getInputStream();
        }
    }
    
    if (resourceStream != null) {
        Files.copy(resourceStream, outFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
        return outFile.getAbsolutePath();
    } else {
        System.out.println("Embedded Resource " + resourceName + " not found.");
    }
    
    return "";
}   

其他回答

这段代码在Eclipse和Exported Runnable JAR中都可以工作

private String writeResourceToFile(String resourceName) throws IOException {
    File outFile = new File(certPath + File.separator + resourceName);

    if (outFile.isFile())
        return outFile.getAbsolutePath();
    
    InputStream resourceStream = null;
    
    // Java: In caso di JAR dentro il JAR applicativo 
    URLClassLoader urlClassLoader = (URLClassLoader)Cypher.class.getClassLoader();
    URL url = urlClassLoader.findResource(resourceName);
    if (url != null) {
        URLConnection conn = url.openConnection();
        if (conn != null) {
            resourceStream = conn.getInputStream();
        }
    }
    
    if (resourceStream != null) {
        Files.copy(resourceStream, outFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
        return outFile.getAbsolutePath();
    } else {
        System.out.println("Embedded Resource " + resourceName + " not found.");
    }
    
    return "";
}   

确保使用正确的分隔符。我用File.separator替换了相对路径中的all /。这在IDE中工作得很好,但是在构建JAR中却不行。

到目前为止(2017年12月),这是我发现的唯一一个在IDE内部和外部都可以工作的解决方案。

使用PathMatchingResourcePatternResolver

注意:它也适用于spring-boot

在这个例子中,我读取了src/main/resources/my_folder中的一些文件:

try {
    // Get all the files under this inner resource folder: my_folder
    String scannedPackage = "my_folder/*";
    PathMatchingResourcePatternResolver scanner = new PathMatchingResourcePatternResolver();
    Resource[] resources = scanner.getResources(scannedPackage);

    if (resources == null || resources.length == 0)
        log.warn("Warning: could not find any resources in this scanned package: " + scannedPackage);
    else {
        for (Resource resource : resources) {
            log.info(resource.getFilename());
            // Read the file content (I used BufferedReader, but there are other solutions for that):
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(resource.getInputStream()));
            String line = null;
            while ((line = bufferedReader.readLine()) != null) {
                // ...
                // ...                      
            }
            bufferedReader.close();
        }
    }
} catch (Exception e) {
    throw new Exception("Failed to read the resources folder: " + e.getMessage(), e);
}

你可以使用类加载器从类路径中读取根路径(开头没有“/”)

InputStream in = getClass().getClassLoader().getResourceAsStream("file.txt"); 
BufferedReader reader = new BufferedReader(new InputStreamReader(in));

我找到了解决办法

BufferedReader br = new BufferedReader(new InputStreamReader(Main.class.getResourceAsStream(path)));

将“Main”替换为您编写它的java类。将“path”替换为jar文件中的路径。

例如,如果你把State1.txt放在com.issac包中。如果你运行的是Linux或Mac,那么输入路径为“/com/issac/state/State1”。如果你运行的是Windows,那么输入路径为“\com\issac\state\State1”。除非出现“文件未找到”异常,否则不要将.txt扩展名添加到文件中。