Filter

基本使用

@Bean
public Filter addHeaderFilter() {
    return new Filter() {
        @Override
        public CompletableFuture<Void> doFilter(AsyncRequest request, AsyncResponse response, FilterChain chain) {
            request.setHeader("foo", "bar");
            return chain.doFilter(request, response);
        }
    };
}

上面的例子将会给所有到来的请求都加上一个固定的Header。

异步`Filter`

@Bean
public Filter filter() {
    return new Filter() {
        @Override
        public CompletableFuture<Void> doFilter(AsyncRequest request, AsyncResponse response, FilterChain chain) {
            return CompletableFuture.runAsync(() -> {
                // do something...
            }).thenCompose(r -> {
                // invoke next filter
                return chain.doFilter(request, response);
            });
        }
    };
}

上面的例子演示了在doFilter(xxx)中进行异步操作，并在该操作完成后回调FilterChain继续执行后续操作。

Tip

上面演示的异步只是开了一个新的线程，实际场景中可使用Netty等实现更优雅的异步方式。

终止`Filter`的执行

当不期望执行后续的Filter时可返回一个CompletableFuture.completedFuture(null)实例。

@Override
public CompletableFuture<Void> doFilter(AsyncRequest request, AsyncResponse response, FilterChain chain) {
    return CompletableFuture.completedFuture(null);
}

Warning

doFilter(xxx)请勿返回null
所有方法都将会在IO线程上调用，尽量不要阻塞，否则将对性能会有较大的影响。

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Last modified March 10, 2022: introduce docsy as the website framework and add docs-v1.0.0 (#120) (79630ff)