问题形容
在Java我的项目中，若须要拜访资源文件，通常应用getClass().getResource("/xxx")和getClass().getResourceAsStream("/")来获取资源文件，后一种形式获取到的是InputStream，个别不会呈现什么问题，然而通过第一种获取资源URL的形式，在IDEA中执行时没有问题，然而在服务器环境执行时，会呈现java.nio.file.FileSystemNotFoundException，之前遇到这个问题我没有在意，只是换成getResourceAsStream后就解决了，然而起初遇到一个须要递归拜访资源文件目录，我应用的Files.walkFileTree办法，间接获取输出流的计划不适宜我，随后发现其实只有是打成jar包执行的时候，通过Files和Path去拜访资源文件，getResource就会抛出FileSystemNotFoundException，并非服务器环境的问题，因为jar包执行时，文件系统与IDE中间接执行时不一样，所以会抛出这个异样。
原始的代码如下：
Path configDir = Paths.get( LocalConfigDataFlowManager.class.getResource( "/" ).toURI().getPath(), "flow-config" );List<Map<String, Object>> config = new ArrayList<>();Files.walkFileTree( configDir, new HashSet<>(), 1, new FileVisitor<Path>() { ......报错信息如下：
java.nio.file.FileSystemNotFoundException at jdk.zipfs/jdk.nio.zipfs.ZipFileSystemProvider.getFileSystem(ZipFileSystemProvider.java:169) at jdk.zipfs/jdk.nio.zipfs.ZipFileSystemProvider.getPath(ZipFileSystemProvider.java:155) at java.base/java.nio.file.Path.of(Path.java:208) at java.base/java.nio.file.Paths.get(Paths.java:97) at ink.andromeda.dataflow.core.flow.ConfigurableDataFlowManager.<init>(ConfigurableDataFlowManager.java:305) at ink.andromeda.dataflow.demo.LocalConfigDataFlowManager.<init>(LocalConfigDataFlowManager.java:25) at ink.andromeda.dataflow.demo.DataFlowDemoApplication.dataFlowManager(DataFlowDemoApplication.java:51) at ink.andromeda.dataflow.demo.DataFlowDemoApplication$$EnhancerBySpringCGLIB$$73b01d37.CGLIB$dataFlowManager$0(<generated>) ............2021-01-07.22:34:39.649 ERROR TraceId[] [main] i.a.d.d.LocalConfigDataFlowManager.visitFileFailed:60 null/flow-configjava.nio.file.NoSuchFileException: null/flow-config at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:92) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:116) at java.base/sun.nio.fs.UnixFileAttributeViews$Basic.readAttributes(UnixFileAttributeViews.java:55) at java.base/sun.nio.fs.UnixFileSystemProvider.readAttributes(UnixFileSystemProvider.java:149) at java.base/java.nio.file.Files.readAttributes(Files.java:1763) at java.base/java.nio.file.FileTreeWalker.getAttributes(FileTreeWalker.java:219) at java.base/java.nio.file.FileTreeWalker.visit(FileTreeWalker.java:276) at java.base/java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:322) at java.base/java.nio.file.Files.walkFileTree(Files.java:2716) at ink.andromeda.dataflow.demo.LocalConfigDataFlowManager.getFlowConfig(LocalConfigDataFlowManager.java:39) at ink.andromeda.dataflow.core.flow.ConfigurableDataFlowManager.reload(ConfigurableDataFlowManager.java:92) at ink.andromeda.dataflow.core.flow.ConfigurableDataFlowManager.init(ConfigurableDataFlowManager.java:56) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) ......解决方案
刚开始试了如下计划：
Path configDir = FileSystems.getDefault().getPath(new UrlResource(this.getClass().getResource("/flow-config").toURI()).toString());然而依然有问题：
2021-01-07.23:06:42.037 ERROR TraceId[] [main] i.a.d.d.LocalConfigDataFlowManager.visitFileFailed:63 URL [jar:file:/Users/windlively/IdeaProjects/data-flow/data-flow-demo/target/data-flow-demo-1.0-SNAPSHOT.jar!/BOOT-INF/classes!/flow-config]java.nio.file.NoSuchFileException: URL [jar:file:/Users/windlively/IdeaProjects/data-flow/data-flow-demo/target/data-flow-demo-1.0-SNAPSHOT.jar!/BOOT-INF/classes!/flow-config] at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:92) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:116) at java.base/sun.nio.fs.UnixFileAttributeViews$Basic.readAttributes(UnixFileAttributeViews.java:55) at java.base/sun.nio.fs.UnixFileSystemProvider.readAttributes(UnixFileSystemProvider.java:149) at java.base/java.nio.file.Files.readAttributes(Files.java:1763) at java.base/java.nio.file.FileTreeWalker.getAttributes(FileTreeWalker.java:219) at java.base/java.nio.file.FileTreeWalker.visit(FileTreeWalker.java:276) at java.base/java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:322) at java.base/java.nio.file.Files.walkFileTree(Files.java:2716) at ink.andromeda.dataflow.demo.LocalConfigDataFlowManager.getFlowConfig(LocalConfigDataFlowManager.java:42) at ink.andromeda.dataflow.core.flow.ConfigurableDataFlowManager.reload(ConfigurableDataFlowManager.java:92) at ink.andromeda.dataflow.core.flow.ConfigurableDataFlowManager.init(ConfigurableDataFlowManager.java:56)于是持续查问材料，在stackoverflow上看到了一个利用Spring的@Value()注解和Spring Resource来拜访资源文件的代替计划，而且提供了遍历资源文件夹的办法。
首先在Bean中退出一个字段并用Value注解注入资源文件的地位：
@Value("classpath:/flow-config/**")private Resource[] flowConfigResources;Spring会主动将classes根目录flow-config文件夹下的资源文件全副注入到flowConfigResources字段中去。
而后批改原先的代码如下：
protected List<Map<String, Object>> getFlowConfig() { return Stream.of(flowConfigResources) .filter(s -> Objects.nonNull(s.getFilename())) .filter(s -> s.getFilename().matches("^sync-config-[\\w-]+?.json$")) .map(flowConfigResource -> { try (InputStream is = flowConfigResource.getInputStream()) { ByteArrayOutputStream os = new ByteArrayOutputStream(); int data; while ((data = is.read()) != -1) os.write(data); //noinspection unchecked return (Map<String, Object>) GSON().fromJson(os.toString(StandardCharsets.UTF_8.name()), new TypeToken<Map<String, Object>>() { }.getType()); } catch (IOException ex) { throw new IllegalStateException(ex); } }) .filter(Objects::nonNull) .collect(Collectors.toList());}过滤和遍历Spring注入的Resource列表，即可读取到此文件夹下所有须要的资源文件，打成jar包之后也可失常运行。