Request的重新组装
在操作request的时候，有一种很常见的方式，就是从自定义的过滤器中从request中取出数据然后使用
@Slf4j
public class TraceIdFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
String traceId = request.getHeader("traceId");
log.info("traceId:{}",traceId);
filterChain.doFilter(request, response);
}
}
网上的一些帖子和在项目中大家都会看到这种用法，如果后续业务中还需要request的话，可能会这么取request
public ServletRequestAttributes getRequestAttributes() {
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
if (requestAttributes == null) {
return null;
}
return (ServletRequestAttributes) requestAttributes;
}
public String getHeadValue(String name) {
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
if (requestAttributes == null) {
return null;
}
HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();
return request.getHeader(name);
}
RequestContextHolder 是Spring中提供的，当Spring判断当请求执行完后，会从 RequestContextHolder 中把这次请求的 request 给清除掉， 这就带来一个问题，如果子线程用的也是这个 request 的话，逻辑还没执行完，主线程直接给清掉了，那子线程的 request 不也跟着没有了吗？
所以需要将 request 重组成一个新的，传递给子线程使用，可以看下在 link-flow 中的过滤器是怎么做的
Request的重组
@Order(HIGHEST_PRECEDENCE)
public class RequestParamContextFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
if (requestAttributes != null) {
requestAttributes = ServiceRequestEnhanceOperation.enhanceRequestAttributes(requestAttributes);
}
BaseParameterHolder.setParameter(WorkConstant.REQUEST_ATTRIBUTES, requestAttributes);
Map<String,Object> newMap = new HashMap<>(BaseParameterHolder.getParameterMap().size());
newMap.putAll(BaseParameterHolder.getParameterMap());
TtlParameterHolder.setParameterMap(newMap);
try {
filterChain.doFilter(request, response);
}finally {
BaseParameterHolder.removeParameter(WorkConstant.REQUEST_ATTRIBUTES);
TtlParameterHolder.removeParameterMap();
}
}
}