WEB-INF目录下文件复制的几种方式

2018年1月31日 10:42:55

工作完写点博客记录下。

需求：从web-inf下拷贝文件到指定目录。

目录结构

直接贴代码

第一种方式，字节流读取

 try { 

                   int index = 0;
                   System.out.println("开始读取");

             File filef = new File("web/WEB-INF/apk/"+channel+".apk");
             System.out.println(filef.getAbsolutePath());

             InputStream inputStream = new FileInputStream(filef.getAbsolutePath());//获取文件所在路径并读入
                   if(inputStream!=null){
                       //读取文件(缓存字节流)
                       BufferedInputStream in = new BufferedInputStream(inputStream);
                       //写入相应的文件
                       BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("web/apk/"+channel+".apk"));
                       //读取数据
                       //一次性取多少字节
                       byte[] bytes = new byte[2048];
                       //接受读取的内容
                       int n = -1;
                       //循环取出数据
                       while ((n = in.read(bytes,0,bytes.length)) != -1) {
                           //转换成字符串
                           String str = new String(bytes,0,n,"GBK");
                           System.out.println(str);
                           //写入相关文件
                           out.write(bytes, 0, n);
                       }
                       //清除缓存
                       out.flush();
                       //关闭流
                       in.close();
                       out.close();
                   }else if(index<=1){

                       index++;
                   }

                  //}
             /*}*/
         } catch (Exception e) {
             e.printStackTrace();
         }

注意读取的文件路径要从web开始写！

第二种方式

　　使用apache的commons的FileUtils

　　jar：commons-io-2.4.jar

使用方式

 @Test
     public void test2(){
         File file2 = new File("web/apk/22.apk");
         File file1 = new File("web/WEB-INF/apk/22.apk");
         System.out.println(file1.getAbsolutePath());
         try {
             FileUtils.copyFile(file1,file2);
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

file1是要读取的路径，file2是要写入的路径

贴一下人家工具类的源码

 /**
      * Copies a file to a new location.
      * <p>
      * This method copies the contents of the specified source file
      * to the specified destination file.
      * The directory holding the destination file is created if it does not exist.
      * If the destination file exists, then this method will overwrite it.
      * <p>
      * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
      * {@code true} tries to preserve the file's last modified
      * date/times using {@link File#setLastModified(long)}, however it is
      * not guaranteed that the operation will succeed.
      * If the modification operation fails, no indication is provided.
      *
      * @param srcFile          an existing file to copy, must not be {@code null}
      * @param destFile         the new file, must not be {@code null}
      * @param preserveFileDate true if the file date of the copy
      *                         should be the same as the original
      *
      * @throws NullPointerException if source or destination is {@code null}
      * @throws IOException          if source or destination is invalid
      * @throws IOException          if an IO error occurs during copying
      * @throws IOException          if the output file length is not the same as the input file length after the copy
      * completes
      * @see #copyFileToDirectory(File, File, boolean)
      * @see #doCopyFile(File, File, boolean)
      */
     public static void copyFile(final File srcFile, final File destFile,
                                 final boolean preserveFileDate) throws IOException {
         checkFileRequirements(srcFile, destFile);
         if (srcFile.isDirectory()) {
             throw new IOException("Source '" + srcFile + "' exists but is a directory");
         }
         if (srcFile.getCanonicalPath().equals(destFile.getCanonicalPath())) {
             throw new IOException("Source '" + srcFile + "' and destination '" + destFile + "' are the same");
         }
         final File parentFile = destFile.getParentFile();
         if (parentFile != null) {
             if (!parentFile.mkdirs() && !parentFile.isDirectory()) {
                 throw new IOException("Destination '" + parentFile + "' directory cannot be created");
             }
         }
         if (destFile.exists() && destFile.canWrite() == false) {
             throw new IOException("Destination '" + destFile + "' exists but is read-only");
         }
         doCopyFile(srcFile, destFile, preserveFileDate);
     }

 /**
      * Internal copy file method.
      * This caches the original file length, and throws an IOException
      * if the output file length is different from the current input file length.
      * So it may fail if the file changes size.
      * It may also fail with "IllegalArgumentException: Negative size" if the input file is truncated part way
      * through copying the data and the new file size is less than the current position.
      *
      * @param srcFile          the validated source file, must not be {@code null}
      * @param destFile         the validated destination file, must not be {@code null}
      * @param preserveFileDate whether to preserve the file date
      * @throws IOException              if an error occurs
      * @throws IOException              if the output file length is not the same as the input file length after the
      * copy completes
      * @throws IllegalArgumentException "Negative size" if the file is truncated so that the size is less than the
      * position
      */
     private static void doCopyFile(final File srcFile, final File destFile, final boolean preserveFileDate)
             throws IOException {
         if (destFile.exists() && destFile.isDirectory()) {
             throw new IOException("Destination '" + destFile + "' exists but is a directory");
         }

         try (FileInputStream fis = new FileInputStream(srcFile);
25              FileChannel input = fis.getChannel();
26              FileOutputStream fos = new FileOutputStream(destFile);
27              FileChannel output = fos.getChannel()) {
             final long size = input.size(); // TODO See IO-386
             long pos = 0;
             long count = 0;
             while (pos < size) {
                 final long remain = size - pos;
                 count = remain > FILE_COPY_BUFFER_SIZE ? FILE_COPY_BUFFER_SIZE : remain;
                 final long bytesCopied = output.transferFrom(input, pos, count);
                 if (bytesCopied == 0) { // IO-385 - can happen if file is truncated after caching the size
                     break; // ensure we don't loop forever
                 }
                 pos += bytesCopied;
             }
         }

         final long srcLen = srcFile.length(); // TODO See IO-386
         final long dstLen = destFile.length(); // TODO See IO-386
         if (srcLen != dstLen) {
             throw new IOException("Failed to copy full contents from '" +
                     srcFile + "' to '" + destFile + "' Expected length: " + srcLen + " Actual: " + dstLen);
         }
         if (preserveFileDate) {
             destFile.setLastModified(srcFile.lastModified());
         }
     }

重点看红色部分，底层还是字节流，没具体看，可能效率上会更高。

能自己写的就别用人家封装好的，即使用了，也要分析人家的实现方式！