声明抛出IOException的Java方法未向上传播异常问题排查

相关方法代码 #

(388) protected String getExtension(BufferedInputStream stream) throws IOException, MimeTypeException {
(389)   TikaConfig config = TikaConfig.getDefaultConfig();
(390)   MediaType mediaType = config.getMimeRepository().detect(stream, new Metadata());
(391)   MimeType mimeType = config.getMimeRepository().forName(mediaType.toString());
(392)   String extension = mimeType.getExtension(); 
(393)   return extension;
(394) }

调用堆栈信息 #

java.io.IOException: The process cannot access the file because another process has locked a portion of the file
The process cannot access the file because another process has locked a portion of the file
    at java.base/java.io.FileInputStream.readBytes(Native Method)
    at java.base/java.io.FileInputStream.read(FileInputStream.java:328)
    at java.base/java.io.BufferedInputStream.fill(BufferedInputStream.java:291)
    at java.base/java.io.BufferedInputStream.read1(BufferedInputStream.java:347)
    at java.base/java.io.BufferedInputStream.implRead(BufferedInputStream.java:420)
    at java.base/java.io.BufferedInputStream.read(BufferedInputStream.java:399)
    at java.base/java.io.FilterInputStream.read(FilterInputStream.java:95)
    at org.apache.tika.mime.MimeTypes.readMagicHeader(MimeTypes.java:325)
    at org.apache.tika.mime.MimeTypes.detect(MimeTypes.java:527)
    at com.mbm.mediaorganizer.RelocateFileVisitor.getExtension(RelocateFileVisitor.java:390)
    at com.mbm.mediaorganizer.RelocateFileVisitor.relocateFile(RelocateFileVisitor.java:163)
    at com.mbm.mediaorganizer.RelocateFileVisitor.visitFile(RelocateFileVisitor.java:79)
    at com.mbm.mediaorganizer.RelocateFileVisitor.visitFile(RelocateFileVisitor.java:1)
    at java.base/java.nio.file.Files.walkFileTree(Files.java:2810)
    at java.base/java.nio.file.Files.walkFileTree(Files.java:2881)
    at com.mbm.mediaorganizer.MediaOrganizer.run(MediaOrganizer.java:214)
    at com.mbm.mediaorganizer.MediaOrganizer.main(MediaOrganizer.java:63)

问题解答 #

这个异常已经向上传播了，你是对调用堆栈的含义产生了误解：

1. 堆栈中的com.mbm.mediaorganizer.RelocateFileVisitor.getExtension(RelocateFileVisitor.java:390)这一行，仅表示异常是在执行这一行调用的第三方detect方法时触发的，并非异常卡在此处未继续传递。
2. 你的getExtension方法已声明throws IOException，所以会直接将第三方方法抛出的IOException向上传递，无需额外捕获处理，这完全符合Java异常处理规则。
3. 从完整堆栈可清晰看到传播路径：异常从MimeTypes.detect抛出后，经getExtension依次传递到relocateFile、visitFile，再进入JDK的Files.walkFileTree方法，最终传到MediaOrganizer.main方法。

内容的提问来源于stack exchange，提问作者mbmast