Codename一个用于附加/合并文件的API

Question

以代码名One合并存储文件，我阐述了此解决方案：

    /**
     * Merges the given list of Storage files in the output Storage file.
     * @param toBeMerged
     * @param output
     * @throws IOException 
     */
    public static synchronized void mergeStorageFiles(List<String> toBeMerged, String output) throws IOException {

        if (toBeMerged.contains(output)) {
            throw new IllegalArgumentException("The output file cannot be contained in the toBeMerged list of input files.");
        }

        // Note: the temporary file used for merging is placed in the FileSystemStorage because it offers the method
        // openOutputStream(String file, int offset) that allows appending to a stream. Storage doesn't have a such method.

        long writtenBytes = 0;
        String tempFile = FileSystemStorage.getInstance().getAppHomePath() + "/tempFileUsedInMerge";
        for (String partialFile : toBeMerged) {
            InputStream in = Storage.getInstance().createInputStream(partialFile);
            OutputStream out = FileSystemStorage.getInstance().openOutputStream(tempFile, (int) writtenBytes);
            Util.copy(in, out);
            writtenBytes = FileSystemStorage.getInstance().getLength(tempFile);
        }
        Util.copy(FileSystemStorage.getInstance().openInputStream(tempFile), Storage.getInstance().createOutputStream(output));
        FileSystemStorage.getInstance().delete(tempFile);
    }

此解决方案基于API FileSystemStorage.openOutputStream(String file, int offset)，这是我发现的唯一允许将文件内容附加到另一个API的API。

还有其他可用于添加或合并文件的API吗？

谢谢

Answer 1

由于您最终将所有内容复制到Storage条目，所以我看不到使用FileSystemStorage作为中间合并工具的价值。

我能想到的唯一原因是输出文件的完整性（例如，如果写入时发生故障），但这也可能在这里发生。您可以通过设置标志来保证完整性，例如创建一个名为“ writeLock”的文件，并在写入成功完成后将其删除。

为清楚起见，我会像这样更简单/更快地进行复制：

try(OutputStream out = Storage.getInstance().createOutputStream(output)) {
    for (String partialFile : toBeMerged) {
        try(InputStream in = Storage.getInstance().createInputStream(partialFile)) {
            Util.copyNoClose(in, out, 8192);
        }
    }
}