源码分析：Tomcat - 请求Header异步获取不到问题

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前言

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1. 为什么需要这个？
请求在结束时，header会清空，异步再从请求中获取header内容，就获取不到了。
             org.apache.coyote.http11.Http11Processor.recycle --- inputBuffer.recycle();
             org.apache.coyote.http11.Http11InputBuffer.recycle --- request.recycle();
             org.apache.coyote.Request.recycle --- headers.recycle();
             org.apache.tomcat.util.http.MimeHeaders.recycle

2. 大小写问题
解析转为小写 --- org.apache.coyote.http11.Http11InputBuffer.parseHeader
            // chr is next byte of header name. Convert to lowercase.
            if (chr >= Constants.A && chr <= Constants.Z) {
                byteBuffer.put(pos, (byte) (chr - Constants.LC_OFFSET));
            }
header 获取忽略大小写 --- org.apache.tomcat.util.http.MimeHeaders.getHeader

上下文-放入

省略其他代码

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@Slf4j
@Order(2)
@Component
public class TokenFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        try {
            ContextUtils.Header.init();

            // [3] 执行下一个拦截器
            filterChain.doFilter(servletRequest, servletResponse);
        } finally {
            ContextUtils.Header.remove();
        }
    }

}


public class AsyncUtils {
    public static <T> CompletableFuture<T> supplyAsync(Supplier<T> supplier) {
        final LinkedCaseInsensitiveMap<String> header = ContextUtils.Header.get();

        return CompletableFuture.supplyAsync(() -> {
            try {
                ContextUtils.Header.set(header);
                return supplier.get();
            } finally {
                ContextUtils.Header.remove();
            }
        }, executor);
    }
}

上下文-获取

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public class UserUtil {

    private static String header(String key) {
        return Opt.ofTry(() -> ContextUtils.Header.get().get(key)).get();
    }

    // ios/android/h5
    public static String platform() {
        return header("platform");
    }

    // 设备ID
    public static String deviceId() {
        return header("deviceId");
    }

    public static String userAgent() {
        return header("User-Agent");
    }
}

上下文-定义

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public class ContextUtils {

    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 请求header ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
    public static class Header {

        private static ThreadLocal<LinkedCaseInsensitiveMap<String>> header = ThreadLocal.withInitial(LinkedCaseInsensitiveMap::new);

        public static void init() {
            LinkedCaseInsensitiveMap<String> value = Header.get();
            UserUtil.request().getHeaderNames().asIterator().forEachRemaining(key -> {
                value.put(key, UserUtil.request().getHeader(key));
            });

            Header.header.set(value);
        }

        public static void set(LinkedCaseInsensitiveMap<String> value) {
            header.set(value);
        }

        public static LinkedCaseInsensitiveMap<String> get() {
            return header.get();
        }

        public static void remove() {
            header.remove();
        }
    }

}