Spring Gateway修改RequestBody启动报错及代码求助

核心问题 #

启动报错The elements [spring.cloud.gateway.routes[0].filters[0].modifyrequestbody.class] were left unbound的原因是：

• 你混淆了内置ModifyRequestBody过滤器和自定义GatewayFilter的配置方式：内置ModifyRequestBody的配置参数中不存在class字段，却在YAML里强行添加，导致Spring无法解析配置。
• 自定义Filter代码存在语法错误，同时逻辑处理不当。

解决方案（两种可选） #

方案一：修复自定义Filter并正确配置 #

1. 修正自定义Filter代码

@Slf4j
public class SomeFilter implements GatewayFilter {

    private final ModifyRequestBodyGatewayFilterFactory factory;

    // 构造函数名必须与类名一致，原代码写为RedirectionFilter是错误的
    public SomeFilter(ModifyRequestBodyGatewayFilterFactory factory) {
        this.factory = factory;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ModifyRequestBodyGatewayFilterFactory.Config cfg = new ModifyRequestBodyGatewayFilterFactory.Config();
        cfg.setContentType("application/json");
        cfg.setRewriteFunction(String.class, String.class, new MyRewriteFunction());

        // 必须返回ModifyRequestBody处理后的Mono，否则会重复执行过滤器链
        return factory.apply(cfg).filter(exchange, chain);
    }
}

2. 注册自定义Filter为Spring Bean

创建配置类将Filter注入Spring容器：

@Configuration
public class GatewayConfig {
    @Bean
    public SomeFilter someFilter(ModifyRequestBodyGatewayFilterFactory factory) {
        return new SomeFilter(factory);
    }
}

3. 修改YAML配置

移除错误的ModifyRequestBody配置块，直接引用自定义Filter的Bean名称：

routes:
  - id: order-route-1
    uri: http://localhost:8999/
    predicates:
      - Path=/some/path1
      - Method=POST
    filters:
      - Name=someFilter  # 对应@Bean方法名

方案二：直接使用内置ModifyRequestBody过滤器（更简洁） #

无需自定义Filter，直接结合自定义RewriteFunction即可：

1. 修正并注册RewriteFunction为Bean

@Slf4j
@Component // 直接注册为Bean
public class MyRewriteFunction implements RewriteFunction<String, String> {

    @Override
    public Publisher<String> apply(ServerWebExchange exchange, String s) {
        try {
            ObjectMapper objectMapper = new ObjectMapper();
            HelloObject obj = objectMapper.readValue(s, HelloObject.class);
            String newBody = objectMapper.writeValueAsString(obj.getData());
            return Mono.just(newBody);
        } catch (Exception e) {
            log.error("Error while parsing body", e);
        }
        return Mono.just(s);
    }
}

2. 修改YAML配置

直接使用内置ModifyRequestBody过滤器，指定RewriteFunction的Bean名称：

routes:
  - id: order-route-1
    uri: http://localhost:8999/
    predicates:
      - Path=/some/path1
      - Method=POST
    filters:
      - ModifyRequestBody:
          contentType: application/json
          rewriteFunction: myRewriteFunction  # 对应Bean名称（类名首字母小写）

额外代码修正 #

MyRewriteFunction原代码存在多余大括号，已在上述代码中修正；同时建议复用同一个ObjectMapper，避免重复创建对象浪费资源。

内容的提问来源于stack exchange，提问作者ha22109