Spring Cloud Gateway中基于请求体动态路由的挑战与替代策略

spring:
  cloud:
    gateway:
      routes:
        - id: route_to_charge_service
          uri: lb://CHARGE-SERVICE # 路由到名为 CHARGE-SERVICE 的服务
          predicates:
            - Header=X-Target-Type, chagre # 当请求头 X-Target-Type 的值为 chagre 时匹配
          filters:
            # 假设原始请求路径是 /api/v1/data，我们想将其转发到 CHARGE-SERVICE 的 /charge/v1/data
            - RewritePath=/api/(?<segment>.*), /charge/${segment} 

        - id: route_to_package_service
          uri: lb://PACKAGE-SERVICE # 路由到名为 PACKAGE-SERVICE 的服务
          predicates:
            - Header=X-Target-Type, package # 当请求头 X-Target-Type 的值为 package 时匹配
          filters:
            # 假设原始请求路径是 /api/v1/data，我们想将其转发到 PACKAGE-SERVICE 的 /package/v1/data
            - RewritePath=/api/(?<segment>.*), /package/${segment}

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.factory.Abstract           GatewayFilterFactory;
import org.springframework.cloud.gateway.filter.factory.ModifyRequestBodyGatewayFilterFactory;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import java.nio.charset.StandardCharsets;
import java.util.Map;

@Component
public class DynamicRouteByBodyGatewayFilterFactory 
       extends AbstractGatewayFilterFactory<DynamicRouteByBodyGatewayFilterFactory.Config> {

    private final ModifyRequestBodyGatewayFilterFactory modifyRequestBodyGatewayFilterFactory;

    public DynamicRouteByBodyGatewayFilterFactory(ModifyRequestBodyGatewayFilterFactory modifyRequestBodyGatewayFilterFactory) {
        super(Config.class);
        this.modifyRequestBodyGatewayFilterFactory = modifyRequestBodyGatewayFilterFactory;
    }

    @Override
    public GatewayFilter apply(Config config) {
        return (exchange, chain) -> {
            // 确保请求方法是 POST/PUT 等包含请求体的类型
            if (exchange.getRequest().getMethod() != HttpMethod.POST && 
                exchange.getRequest().getMethod() != HttpMethod.PUT) {
                return chain.filter(exchange);
            }

            // 使用 ModifyRequestBodyGatewayFilterFactory 来处理请求体
            // 这里我们创建一个临时的ModifyRequestBody过滤器来读取并处理body
            return modifyRequestBodyGatewayFilterFactory.apply(new ModifyRequestBodyGatewayFilterFactory.Config()
                .setInClass(String.class) // 假设请求体是字符串
                .setOutClass(String.class) // 输出也为字符串
                .setNewContentFunction(String.class, (exchange1, body) -> {
                    // 在这里解析请求体 'body'
                    // 例如，如果body是JSON: {"firstField": "chagre"}
                    try {
                        // 简单的字符串解析，实际应用中应使用Jackson等库
                        if (body.contains("\"firstField\":\"chagre\"")) {
                            // 添加自定义头部，供后续路由谓词使用
                            exchange1.getRequest().mutate().header("X-Dynamic-Route-Target", "chagre").build();
                        } else if (body.contains("\"firstField\":\"package\"")) {
                            exchange1.getRequest().mutate().header("X-Dynamic-Route-Target", "package").build();
                        }
                    } catch (Exception e) {
                        // 处理解析异常
                        e.printStackTrace();
                    }
                    return Mono.just(body); // 返回原始请求体，确保下游服务能收到
                })
            ).filter(exchange, chain);
        };
    }

    public static class Config {
        // 配置项，如果需要
    }
}

spring:
  cloud:
    gateway:
      routes:
        - id: dynamic_route_by_body_charge
          uri: lb://CHARGE-SERVICE
          predicates:
            - Header=X-Dynamic-Route-Target, chagre
          filters:
            - DynamicRouteByBody # 应用我们自定义的过滤器
            - RewritePath=/api/(?<segment>.*), /charge/${segment}
        - id: dynamic_route_by_body_package
          uri: lb://PACKAGE-SERVICE
          predicates:
            - Header=X-Dynamic-Route-Target, package
          filters:
            - DynamicRouteByBody
            - RewritePath=/api/(?<segment>.*), /package/${segment}