无消耗访问HTTP Servlet请求参数
问题：
访问多个HTTP请求时Servlet 过滤器中的参数，初始参数访问会消耗这些参数，使其无法用于后续使用。这个问题在参数驻留在请求正文中的 POST 请求中尤其容易出现。
解决方案：
要访问参数而不消耗它们，您可以扩展 HttpServletRequestWrapper 并实现自定义方法缓存输入流：
public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
private ByteArrayOutputStream cachedBytes;
public MultiReadHttpServletRequest(HttpServletRequest request) {
super(request);
}
@Override
public ServletInputStream getInputStream() throws IOException {
if (cachedBytes == null)
cacheInputStream();
return new CachedServletInputStream(cachedBytes.toByteArray());
}
@Override
public BufferedReader getReader() throws IOException{
return new BufferedReader(new InputStreamReader(getInputStream()));
}
private void cacheInputStream() throws IOException {
cachedBytes = new ByteArrayOutputStream();
IOUtils.copy(super.getInputStream(), cachedBytes);
}
private static class CachedServletInputStream extends ServletInputStream {
private final ByteArrayInputStream buffer;
public CachedServletInputStream(byte[] contents) {
this.buffer = new ByteArrayInputStream(contents);
}
@Override
public int read() {
return buffer.read();
}
// ... Implementation for newer versions of ServletInputStream interface
}
}通过使用此类包装原始请求，您可以访问在过滤器链内外多次缓存输入流，允许 getParameterXXX 和 doMyThing 等自定义方法读取参数：
public class MyFilter implements Filter {
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
MultiReadHttpServletRequest multiReadRequest = new MultiReadHttpServletRequest((HttpServletRequest) request);
doMyThing(multiReadRequest.getInputStream());
chain.doFilter(multiReadRequest, response);
}
}以上是如何无消耗地多次访问HTTP Servlet请求参数？的详细内容。更多信息请关注PHP中文网其他相关文章！
