java - 使用 Java8 Base64 解码器的 IllegalArgumentException

Question

我想使用 Base64.java 来编码和解码文件。 Encode.wrap(InputStream) 和 decode.wrap(InputStream) 工作但运行缓慢。所以我使用了以下代码。

public static void decodeFile(String inputFileName,
        String outputFileName)
        throws FileNotFoundException, IOException {

    Base64.Decoder decoder = Base64.getDecoder();
    InputStream in = new FileInputStream(inputFileName);
    OutputStream out = new FileOutputStream(outputFileName);

    byte[] inBuff = new byte[BUFF_SIZE];  //final int BUFF_SIZE = 1024;
    byte[] outBuff = null;
    while (in.read(inBuff) > 0) {
        outBuff = decoder.decode(inBuff);
        out.write(outBuff);
    }
    out.flush();
    out.close();
    in.close();
}

但是，它总是抛出

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Input byte array has wrong 4-byte ending unit
    at java.util.Base64$Decoder.decode0(Base64.java:704)
    at java.util.Base64$Decoder.decode(Base64.java:526)
    at Base64Coder.JavaBase64FileCoder.decodeFile(JavaBase64FileCoder.java:69)
    ...

在我将 final int BUFF_SIZE = 1024; 更改为 final int BUFF_SIZE = 3*1024; 后，代码可以正常工作。由于“BUFF_SIZE”也用于对文件进行编码，我认为编码的文件有问题(1024 % 3 = 1，这意味着在文件中间添加了填充)。

此外，正如@Jon Skeet 和@Tagir Valeev 提到的，我不应该忽略 InputStream.read() 的返回值。所以，我修改了如下代码。

(但是，我不得不提到代码确实比使用 wrap() 运行得快得多。我注意到了速度差异，因为我已经编码并大量使用了 Base64.encodeFile()/decodeFile( ) 早在 jdk8 发布之前。现在，我的 buffed jdk8 代码运行速度与我的原始代码一样快。所以，我不知道 wrap() 发生了什么... )

public static void decodeFile(String inputFileName,
        String outputFileName)
        throws FileNotFoundException, IOException
{

    Base64.Decoder decoder = Base64.getDecoder();
    InputStream in = new FileInputStream(inputFileName);
    OutputStream out = new FileOutputStream(outputFileName);

    byte[] inBuff = new byte[BUFF_SIZE];
    byte[] outBuff = null;
    int bytesRead = 0;
    while (true)
    {
        bytesRead = in.read(inBuff);
        if (bytesRead == BUFF_SIZE)
        {
            outBuff = decoder.decode(inBuff);
        }
        else if (bytesRead > 0)
        {
            byte[] tempBuff = new byte[bytesRead];
            System.arraycopy(inBuff, 0, tempBuff, 0, bytesRead);
            outBuff = decoder.decode(tempBuff);
        }
        else
        {
            out.flush();
            out.close();
            in.close();
            return;
        }
        out.write(outBuff);
    }
}

特别感谢@Jon Skeet 和@Tagir Valeev。

Answer 1

我强烈怀疑问题是您忽略了 InputStream.read 的返回值，而不是检查流的结尾。所以这个:

while (in.read(inBuff) > 0) {
    // This always decodes the *complete* buffer
    outBuff = decoder.decode(inBuff);
    out.write(outBuff);
}

应该是

int bytesRead;
while ((bytesRead = in.read(inBuff)) > 0) {
    outBuff = decoder.decode(inBuff, 0, bytesRead);
    out.write(outBuff);
}

不过，我预计这会比使用wrap 更快。​​