上傳文件亂碼，GBK轉UTF-8

最近遇到這樣一個問題，我上傳文件沒有轉換字符集windows默認GBK，結果當我須要讀文件顯示時用UTF-8轉固然會出現亂碼，爲了解決這個問題，我就將上傳時文件一同也轉成UTF-8了這樣就不會亂碼了，上傳時轉換字符集方法以下：

String root = filePath;// 上傳路徑
File rootFile = new File(root);
// 路徑不存在先建立路徑
if (!rootFile.exists()) {
rootFile.mkdirs();
}
// 獲取後綴type
String suffix = domain.getSuffixName();
// 新文件名
String strNewName = domain.getScriptName().trim() + domain.getVersionName().trim() + "."
+ suffix;
domain.setScriptUrl("/" + strNewName);
File destFile;
String destFilePath=root+"/"+strNewName;
destFile = new File(root, strNewName);
OutputStream outputStream;
outputStream = new FileOutputStream(destFile);
// file是上傳過來的文件，存放爲臨時tmp
File file = domain.getFile();

String context = "";
InputStreamReader isr;
isr = new InputStreamReader(new FileInputStream(file), "GBK");
BufferedReader br = new BufferedReader(isr);
String line;

while ((line = br.readLine()) != null) {
context += line + "\r\n";
System.out.println(line);
}

br.close();

byte[] content = context.getBytes();
context = new String(content, "UTF-8");

BufferedWriter writer;

FileOutputStream fos = new FileOutputStream(destFilePath, true);
System.out.println(root+"/"+strNewName);
writer = new BufferedWriter(new OutputStreamWriter(fos, "UTF-8"));
writer.append(context);
writer.close();