用java代码实现在gateway响应头中添加Content-Type等于application/json

可以使用以下代码实现：

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.http.MediaType;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

@Component
public class ContentTypeFilter implements GlobalFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        ServerHttpResponse response = exchange.getResponse();

        response.getHeaders().setContentType(MediaType.APPLICATION_JSON);

        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        return -1;
    }
}

这个过滤器会在所有请求前面添加 Content-Type 响应头，并设置为 application/json 。