在网关过滤器里面怎么修改请求参数

要修改请求参数，可以在网关过滤器中使用Spring Cloud Gateway提供的请求修改工具类ServerWebExchangeDecorator，具体步骤如下：

1. 注入ServerWebExchangeDecoratorFactory类型的bean：

@Bean
public ServerWebExchangeDecoratorFactory serverWebExchangeDecoratorFactory() {
    return new MyServerWebExchangeDecoratorFactory();
}

2. 实现ServerWebExchangeDecoratorFactory接口，返回自定义的ServerWebExchangeDecorator：

public class MyServerWebExchangeDecoratorFactory implements ServerWebExchangeDecoratorFactory {
    @Override
    public ServerWebExchangeDecorator decorate(ServerWebExchange exchange) {
        return new MyServerWebExchangeDecorator(exchange);
    }
}

3. 实现自定义的ServerWebExchangeDecorator，通过修改ServerHttpRequest对象中的请求参数来修改请求参数。例如，将请求中的name参数改为"world"：

public class MyServerWebExchangeDecorator extends ServerWebExchangeDecorator {
    public MyServerWebExchangeDecorator(ServerWebExchange delegate) {
        super(delegate);
    }

    @Override
    public ServerHttpRequest getRequest() {
        ServerHttpRequest request = super.getRequest();
        MultiValueMap<String, String> queryParams = request.getQueryParams();
        if (queryParams.containsKey("name")) {
            queryParams.put("name", Arrays.asList("world"));
            request = new ServerHttpRequestDecorator(request) {
                @Override
                public MultiValueMap<String, String> getQueryParams() {
                    return queryParams;
                }
            };
        }
        return request;
    }
}

以上就是在网关过滤器中修改请求参数的方法。