java读取InputStream输入流后输出String字符串

功能：例子中输出字符编码为GBK，输入流保护 50KB，读取InputStream输入流后输出String字符串。

    private static final String DEFAULT_ENCODING = "GBK";//编码
    private static final int PROTECTED_LENGTH = 51200;// 输入流保护 50KB
    
    public String readInfoStream(InputStream input) throws Exception {
        if (input == null) {
            throw new Exception("输入流为null");
        }
        //字节数组
        byte[] bcache = new byte[2048];
        int readSize = 0;//每次读取的字节长度
        int totalSize = 0;//总字节长度
        ByteArrayOutputStream infoStream = new ByteArrayOutputStream();
        try {
            //一次性读取2048字节
            while ((readSize = (bcache)) > 0) {
                totalSize += readSize;
                if (totalSize > PROTECTED_LENGTH) {
                    throw new Exception("输入流超出50K大小限制");
                }
                //将bcache中读取的input数据写入infoStream
                (bcache,0,readSize);
            }
        } catch (IOException e1) {
            throw new Exception("输入流读取异常");
        } finally {
            try {
                //输入流关闭
                ();
            } catch (IOException e) {
                throw new Exception("输入流关闭异常");
            }
        }

        try {
            return (DEFAULT_ENCODING);
        } catch (UnsupportedEncodingException e) {
            throw new Exception("输出异常");
        }
    }