响应式弹簧查询参数 [英] Reactive Spring Query Parameters

问题描述

我的Spring Reactive Web API应该能够基于查询参数进行过滤，但是我正在努力做到这一点.

My Spring Reactive Web API should be able to filter based on query parameters but I'm struggling to get this right.

GET /v1/address?type=business

应在系统中返回所有类型为"business"的地址(仅作为示例，因为我没有发布实际要求).如果不存在该参数，则只需返回所有地址即可.

Should return all addresses of type 'business' in the system (just an example since I'm not posting the actual requirements). If the parameter is absent then just return all addresses.

[
  { "id" : 1, "type" : "business", "street" : "..."},
  { "id" : 2, "type" : "business", "street" : "..."},
  ...
}

我正在使用路由器功能来映射请求:

I'm using Router functions to map the request:

public RouterFunction<ServerResponse> route(AddressHandler handler) {
    return route(GET("/v1/address"), handler::getAddresses);
}

但是我正在努力确定如何检查参数，如果不存在该参数，则返回所有地址.

But I'm struggling to determine how to check for the parameter and, if it isn't present, to return all addresses.

class AddressHandler {
    Mono<ServerResponse> getAddressesFilteredOrNot(ServerRequest request) {
        Optional<String> addressType = request.getQueryParam("type");

        ...
    }
}

现在Optional.ifPresent()无法正常工作，我无法从方法中返回:

Now the Optional.ifPresent() isn't going to work, I can't return from the method:

class AddressHandler {
    Mono<ServerResponse> getAddressesFilteredOrNot(ServerRequest request) {
        Optional<String> addressType = request.getQueryParam("type");

        // invalid
        addressType.ifPresent(addrType -> {
            return ServerResponse.ok()
                .body(this.service.getAddressByType(addrType),
                   Address.class);
    });
}

我也不能在参数上切换ifEmpEmpty()，因为它抛出NullPointerException:

Also I can't switchIfEmpty() on the parameter since it throws a NullPointerException:

class AddressHandler {
    Mono<ServerResponse> getAddressesFilteredOrNot(ServerRequest request) {
        Optional<String> addressType = request.getQueryParam("type");

        // also invalid
        return Mono.justOrEmpty(addressType.orElse(""))
               .flatMap(addrType -> ServerResponse.ok().body(this.service.getAddressByType(addrType), Address.class)
               .switchIfEmpty(ServerResponse.ok().body(this.service.getAllAddresses(), Address.class));
    });
}

使用查询参数(如果存在)又使用getAllAddresses()方法的流程是什么?真的有可能吗?

What's the flow to use query parameters if they are present and fall back on the getAllAddresses() method? Is it actually possible?

推荐答案

您可以使用Optional的orElse()或orElseGet()功能来调用替代方法.例如:

You can use the orElse() or orElseGet() functionality of Optional to invoke an alternative method. For example:

request
    .getQueryParam("type")
    .map(type -> service.getAddressByType(type))
    .orElseGet(() -> service.getAllAddresses());

在这种情况下，orElseGet()更有意义，因为它是延迟调用的.请注意，尽管这两个方法应该具有相同的返回类型，所以可能是Flux<Address>.

In this case, orElseGet() makes more sense, because it's lazily invoked. Be aware though that both methods should have the same return type, so probably Flux<Address>.

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