MD5签署HttpServletResponse
问题内容：
我正在寻找一种检查a的内容HttpServletResponse以使用MD5哈希对其进行签名的方法。
伪代码可能看起来像这样
process(Response response, Request request){
defaultProcessingFor(response,request);
dispatcher.handle(response,request);
// Here I want to read the contents of the Response object (now filled with data) to create a MD5 hash with them and add it to a header.
}
那可能吗？
问题答案：
是的，那是可能的。您需要借助以下方法来修饰响应：在HttpServletResponseWrapper其中，您可以用ServletOutputStream自定义实现替换，该实现将字节写入MD5摘要和“原始”输出流。最后提供一个访问器以获得最终的MD5和。
更新 我只是为了好玩而已，下面是一个启动示例：
响应包装器：
public class MD5ServletResponse extends HttpServletResponseWrapper {
private final MD5ServletOutputStream output;
private final PrintWriter writer;
public MD5ServletResponse(HttpServletResponse response) throws IOException {
super(response);
output = new MD5ServletOutputStream(response.getOutputStream());
writer = new PrintWriter(output, true);
}
public PrintWriter getWriter() throws IOException {
return writer;
}
public ServletOutputStream getOutputStream() throws IOException {
return output;
}
public byte[] getHash() {
return output.getHash();
}
}
MD5输出流：
public class MD5ServletOutputStream extends ServletOutputStream {
private final ServletOutputStream output;
private final MessageDigest md5;
{
try {
md5 = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new ExceptionInInitializerError(e);
}
}
public MD5ServletOutputStream(ServletOutputStream output) {
this.output = output;
}
public void write(int i) throws IOException {
byte[] b = { (byte) i };
md5.update(b);
output.write(b, 0, 1);
}
public byte[] getHash() {
return md5.digest();
}
}
如何使用它：
// Wrap original response with it:
MD5ServletResponse md5response = new MD5ServletResponse(response);
// Now just use md5response instead or response, e.g.:
dispatcher.handle(request, md5response);
// Then get the hash, e.g.:
byte[] hash = md5response.getHash();
StringBuilder hashAsHexString = new StringBuilder(hash.length * 2);
for (byte b : hash) {
hashAsHexString.append(String.format("%02x", b));
}
System.out.println(hashAsHexString); // Example af28cb895a479397f12083d1419d34e7.
