上传文件时出现 IndexOutOfBoundsException - Java

Question

我在上传 zip 文件时遇到 IndexOutOfBoundsException。可能是什么原因？我该如何解决？

代码：-

    String sf="";
    String contentType = req.getContentType();
    DataInputStream in = new DataInputStream(req.getInputStream());
    int formDataLength = req.getContentLength();
    byte dataBytes[] = new byte[formDataLength];
    int byteRead = 0;
    int totalBytesRead = 0;
    while (totalBytesRead < formDataLength) {
        byteRead = in.read(dataBytes, totalBytesRead, formDataLength);
        totalBytesRead += byteRead;
    }
    String file = new String(dataBytes);
    String saveFile = file.substring(file.indexOf("filename=\"") + 10);
    saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
    saveFile = saveFile.substring(saveFile.lastIndexOf("\\") + 1,saveFile.indexOf("\""));
    int lastIndex = contentType.lastIndexOf("=");
    String boundary = contentType.substring(lastIndex + 1,contentType.length());
    int pos;
    pos = file.indexOf("filename=\"");
    pos = file.indexOf("\n", pos) + 1;
    pos = file.indexOf("\n", pos) + 1;
    pos = file.indexOf("\n", pos) + 1;
    int boundaryLocation = file.indexOf(boundary, pos) - 4;
    int startPos = ((file.substring(0, pos)).getBytes()).length;
    int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;
    sf = "../" + File.separator + saveFile;
    FileOutputStream fileOut = new FileOutputStream(sf);
    fileOut.write(dataBytes, startPos, (endPos - startPos));  //----- Exception occurs on this line.
    fileOut.flush();
    fileOut.close();

Stacktrace：-

java.lang.IndexOutOfBoundsException
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:297)
at com.apprika.servlets.UpgradePatchServlet.uploadFile(UpgradePatchServlet.java:77)
at com.apprika.servlets.UpgradePatchServlet.upgradeServer(UpgradePatchServlet.java:40)
at com.apprika.servlets.UpgradePatchServlet.doPost(UpgradePatchServlet.java:30)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:636)

服务器在 Linux 上运行并从 Windows 上传文件。

---

我已经尝试过 apache commons 文件上传但仍然没有成功。

    try {
                 DiskFileItemFactory factory = new DiskFileItemFactory();
                 ServletFileUpload upload = new ServletFileUpload(factory);
                 List<FileItem> items = upload.parseRequest(req);
                 for (FileItem item : items) {
                    if (!item.isFormField()) {
                        InputStream is = item.getInputStream();
                        FileOutputStream os = new FileOutputStream("/up/" + item.getName());
                        byte[] b = new byte[4096];
                        int bytesRead = 0;
                        while ((bytesRead = is.read(b)) != -1) {
                            os.write(b, 0, bytesRead);
                        }
                        os.flush();
                        os.close();
                        is.close();
                    }
                 }
            }catch (Exception e) {
                e.printStackTrace();
            }

现在它给出错误 java.io.FileNotFoundException: /up (Is a directory) `

Answer 1

您正在将上传的字节转换为字符串，而不指定编码。服务器上的默认编码不必与上传时使用的编码相同。
因此，不能保证字符串长度与字节数组长度相同，因此根据字符串计算该数组的偏移量可能会导致各种问题。

我建议使用类似 Apache Commons Fileupload 的东西，而不是尝试自己完成所有解析以获取所有内容细节正确并不容易。
一个很好的起点是这个答案：如何将文件上传到使用 JSP/Servlet 的服务器？

Answer 2

问题在于如何提取 startPos 和 endPos 值，从而导致无效的偏移量。我建议您在调试器中仔细检查提取的值，您会发现解析表单数据的代码有问题。

Answer 3

更改以下行并尝试 ..

String file = new String(dataBytes); 

to

String file = new String(dataBytes,"CP1256");

和

int startPos = ((file.substring(0, pos)).getBytes()).length; 

to

int startPos = ((file.substring(0, pos)).getBytes("CP1256")).length;

和

int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length; 

to

int endPos = ((file.substring(0, boundaryLocation)).getBytes("CP1256")).length;