http_middleware_base.hpp

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#pragma once
 
/// @file userver/server/middlewares/http_middleware_base.hpp
/// @brief Base classes for implementing custom middlewares
 
#include <memory>
 
#include <userver/components/component_base.hpp>
#include <userver/yaml_config/schema.hpp>
#include <userver/yaml_config/yaml_config.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace server {
 
namespace request {
class RequestContext;
}
 
namespace http {
class HttpRequest;
}
 
namespace handlers {
class HttpHandlerBase;
}
 
/// HTTP server middlewares
namespace middlewares {
 
/// @ingroup userver_middlewares userver_base_classes
///
/// @brief Base class for a http middleware
class HttpMiddlewareBase {
public:
    HttpMiddlewareBase();
    virtual ~HttpMiddlewareBase();
 
protected:
    /// @brief Override this method to implement a middleware logic
    virtual void HandleRequest(http::HttpRequest& request, request::RequestContext& context) const = 0;
 
    /// @brief The method to invoke the next middleware in a pipeline
    void Next(http::HttpRequest& request, request::RequestContext& context) const;
 
private:
    friend class handlers::HttpHandlerBase;
 
    std::unique_ptr<HttpMiddlewareBase> next_{nullptr};
};
 
/// @ingroup userver_middlewares userver_base_classes
///
/// @brief Base class for a http middleware-factory
class HttpMiddlewareFactoryBase : public components::ComponentBase {
public:
    HttpMiddlewareFactoryBase(const components::ComponentConfig&, const components::ComponentContext&);
 
    std::unique_ptr<HttpMiddlewareBase>
    CreateChecked(const handlers::HttpHandlerBase& handler, yaml_config::YamlConfig middleware_config) const;
 
protected:
    /// @brief This method should return the schema of a middleware configuration,
    /// if any. You may override it
    virtual yaml_config::Schema GetMiddlewareConfigSchema() const { return yaml_config::Schema::EmptyObject(); }
 
    /// @brief Override this method to create an instance of a middleware
    virtual std::unique_ptr<HttpMiddlewareBase>
    Create(const handlers::HttpHandlerBase&, yaml_config::YamlConfig middleware_config) const = 0;
};
 
/// @ingroup userver_middlewares
///
/// @brief A short-cut for defining a middleware-factory
template <typename Middleware>
class SimpleHttpMiddlewareFactory final : public HttpMiddlewareFactoryBase {
public:
    static constexpr std::string_view kName = Middleware::kName;
 
    using HttpMiddlewareFactoryBase::HttpMiddlewareFactoryBase;
 
private:
    std::unique_ptr<HttpMiddlewareBase> Create(const handlers::HttpHandlerBase& handler, yaml_config::YamlConfig)
        const override {
        return std::make_unique<Middleware>(handler);
    }
};
 
}  // namespace middlewares
}  // namespace server
 
template <typename Middleware>
inline constexpr bool components::kHasValidate<server::middlewares::SimpleHttpMiddlewareFactory<Middleware>> = true;
 
template <typename Middleware>
inline constexpr auto components::kConfigFileMode<server::middlewares::SimpleHttpMiddlewareFactory<Middleware>> =
    ConfigFileMode::kNotRequired;
 
USERVER_NAMESPACE_END