java---积累---修改File文件的权限

使用上传文件的代码如下:

	private static final int ALLOW_DOWNLOAD_COUNT = 2;

	private static Map downloadRecordMap = new HashMap();

	private String barcodeFilePathPrefix="/data/result";

	/**
	 * 
	 * 判断文件是否存在
	 *
	 */
	@RequestMapping("/sampleFile/exists")
	@ResponseBody
	public Object existsFile(String fileName) {
		File file = new File(barcodeFilePathPrefix, fileName);
		if (file.exists()) {
			return AjaxResult.RESULT_SUCCESS;
		} else {
			return AjaxResult.RESULT_ERROR;
		}
	}

	/**
	 * 
	 * 样本文件上传
	 * 
	 */
	@RequestMapping("/sampleFile/upload")
	@ResponseBody
	public Object fileupload(HttpServletRequest request, @RequestParam("sampleFile") CommonsMultipartFile sampleFile) {
		AdminUser adminUser = (AdminUser) request.getSession().getAttribute("nowManager");
		String name = (adminUser != null ? adminUser.getUsername().toString() : "未登录");
		try {
			String fileName = sampleFile.getOriginalFilename();
			File destfile = new File(barcodeFilePathPrefix, fileName);
			SampleFileLog sampleFileLog=new SampleFileLog();
			sampleFileLog.setAction("上传文件"+fileName);
			sampleFileLog.setOperator(name);
			sampleFileLog.setTime(new Date());
			logMongoTemplate.save(sampleFileLog);
			if (!destfile.exists()) { // 文件不存在
				destfile.createNewFile();
				copyFile(sampleFile.getInputStream(), destfile);
			} else { // 文件存在
				copyFile(sampleFile.getInputStream(), destfile);
			}
		} catch (IOException e) {
			e.printStackTrace();
			return AjaxResult.resultError(e.getMessage());
		}
		return AjaxResult.RESULT_SUCCESS;
	}

	@RequestMapping("/sampleFile/download")
	public void fileDownload(HttpServletRequest request, @RequestParam("fileName") String fileName,
			HttpServletResponse response) throws IOException {

		AdminUser adminUser = (AdminUser) request.getSession().getAttribute("nowManager");
		String name = (adminUser != null ? adminUser.getUsername().toString() : "未登录");
		SampleFileLog sampleFileLog=new SampleFileLog();
		sampleFileLog.setAction("下载文件"+fileName);
		sampleFileLog.setOperator(name);
		sampleFileLog.setTime(new Date());
		logMongoTemplate.save(sampleFileLog);
		int i = downloadRecordMap.get(name)==null?0:downloadRecordMap.get(name);
		if (i > ALLOW_DOWNLOAD_COUNT) {
			response.getWriter()
					.println("\r\n" + "\r\n" + " \r\n" + "\r\n"
							+ "\r\n" + "\r\n" + "  
超过下载次数,请联系管理员
\r\n" + "\r\n"
							+ "\r\n" + "");
			return;
		}
		i = i+1;
		downloadRecordMap.put(name, i);
		try {
			File file = new File(barcodeFilePathPrefix, fileName);
			if (file.exists()) {
				response.setHeader("content-disposition",
						"attachment;filename=" + URLEncoder.encode(file.getName(), "UTF-8"));

				StringBuffer buffer = new StringBuffer();
				BufferedReader fileInput = new BufferedReader(new FileReader(file));
				String line = null;
				while (StringUtils.isNotBlank(line = fileInput.readLine())) {
					buffer.append(line + "\n");
				}
				response.getWriter().write(buffer.toString());
				fileInput.close();
				return;
			}
		} catch (IOException e) {
			e.printStackTrace();
		}

		response.getWriter().println("\r\n" + "\r\n" + "\r\n" + "\r\n"
				+ "\r\n" + "\r\n" + "  
没找到文件
\r\n" + "\r\n" + "\r\n" + "");
	}




	/**
	 * 文件复制
	 * 
	 * @param sourceInputStream
	 * @param destFile
	 * @throws IOException
	 */
	private void copyFile(InputStream sourceInputStream, File destFile) throws IOException {
		BufferedReader sourceReader = new BufferedReader(new InputStreamReader(sourceInputStream));
		BufferedWriter destWriter = new BufferedWriter(new FileWriter(destFile));
		String line = null;
		while ((line = sourceReader.readLine()) != null) {
			destWriter.write(line);
			destWriter.newLine();
		}
		sourceReader.close();
		destWriter.close();
	}

可能遇到的问题—上传的文件其他程序和用户无法读取—Permission denied

原因是 调用createNewFile（）方法默认的权限是644

在java中修改File权限的几种方式

方案一 使用File的方法

import java.io.File; 
2.import java.io.IOException; 


public class FilePermission  
{ 
    public static void main( String[] args ) 
    {    
        try { 
            File file = new File("/home/test3.txt"); 
          if (file.createNewFile()){ 
              System.out.println("File is created!"); 
             file.setExecutable(true);//设置可执行权限 
             file.setReadable(true);//设置可读权限 
             file.setWritable(true);//设置可写权限 
             System.out.println("is execute allow : " + file.canExecute()); 
             System.out.println("is read allow : " + file.canRead()); 
              System.out.println("is write allow : " + file.canWrite()); 
          }else{ 
              System.out.println("File already exists."); 
         } 
     } catch (IOException e) { 
          e.printStackTrace();
 
        } 
    }

方案二 调用系统层面的shell命令chmod运行

Runtime runtime = getRuntime();
String command = "chmod 770 " + dirPath;
try {
    Process process = runtime.exec(command);
    process.waitFor();
    int existValue = process.exitValue();
    if(existValue != 0){
        logger.log(Level.SEVERE, "Change file permission failed.");
        }
     } catch (Exception e) {
        logger.log(Level.SEVERE, "Command execute failed.", e);
     }

注意 该使用该方式时，路径值不能包含空格和分号，否则会造成安全风险。如下:
当dirPath带有空格如下:

dirPath = /home/a    aa.txt

当我们运行

chmod 770 /home/a    aa.txt

实际运行的命令效果等同于

chmod 770 /home/a
chmod 770 aa.txt

/home/a整个目录都会被修改成770权限，不符合预期只修改一个文件。

方案三–NIO方式

private void changeFolderPermission(File dirFile) throws IOException {
    Set perms = new HashSet();
    perms.add(PosixFilePermission.OWNER_READ);
    perms.add(PosixFilePermission.OWNER_WRITE);
    perms.add(PosixFilePermission.OWNER_EXECUTE);
    perms.add(PosixFilePermission.GROUP_READ);
    perms.add(PosixFilePermission.GROUP_WRITE);
    perms.add(PosixFilePermission.GROUP_EXECUTE);
    try {
        Path path = Paths.get(dirFile.getAbsolutePath());
        Files.setPosixFilePermissions(path, perms);
    } catch (Exception e) {
        logger.log(Level.SEVERE, "Change folder " + dirFile.getAbsolutePath() + " permission failed.", e);
        }
    }

参考链接:
https://www.jb51.net/article/167122.htm