samples

HTTP Gateway samples

Sample projets that uses most of the Gateway components

Basic HTTP Gateway

This example shows a HTTP Gateway with:

• Clients authentication with API key
• Client access control to services by:
  • List of routes
  • List of services
  • List of groups of routes
• Remote services with and without authentication
• Rewrite path on the Gateway for a specific service endpoint
• Downstream and upstream logging

The example is composed of:

• The HTTP Gateway class: SampleBasic
• The configuration file application.conf, which is the default configuration file used
• The integration test class (with a mock server): SampleBasicTest

Note that it is possible to override config property per environment. For example to override the base URL of a service depending on the environment, it is possible to have:

• The base config file application.conf containing:

test-service = {
  service-id = "test-service"
  base-url = "http://localhost:4567"
  auth = {
    type = "basic"
    userId = "test-auth"
    password = "auth-password"
  }
  routes = [
    {route-id = "fetch-pets", method = "GET", path = "/pets"}
    {route-id = "fetch-pet", method = "GET", path = "/pets/{id}"}
    {route-id = "fetch-pet-friends", method = "GET", path = "/pets/{id}/friends"}
    {route-id = "add-pet", method = "POST", path = "/pets"}
  ]
}

http-gateway = {
    remote-services = [
        ${test-service}
        {
            service-id = "other-service"
            base-url = "http://localhost:4567/other-service"
            routes = [
                {route-id = "route-sample", method = "GET", path = "/route-sample"}
            ]
        }
    ]
    # ...
}

• The staging config file staging.conf containing:

include classpath("application.conf")

http-gateway = {
    remote-services = [
        ${test-service} {
            base-url = "https://staging.test-service.com"
        }
    ]
}

For more information about config loading, see the Config library file loading behavior documentation.

Moreover, config resolution can be debugged this way:

ConfigRenderOptions options = ConfigRenderOptions
  .defaults()
  .setJson(false)           // false: HOCON, true: JSON
  .setOriginComments(false) // true: add comment showing the origin of a value
  .setComments(true)        // true: keep original comment
  .setFormatted(true);       // true: pretty-print result
System.out.println(configLoader.getHttpGatewayConfig().root().render(options));

Custom client dimension

This example has everything from the basic sample and shows how to restrict clients by a custom dimension. In this example, this dimension is represented by the notion of "tenant":

• A client is associated with one or multiple tenants in the configuration file
• The HTTP Gateway verifies that clients:
  • Supply the custom header X-Tenants with the name/id of the tenant
  • That the supplied tenant is associated to the client in the configuration file
• The HTTP Gateway then forwards this custom header value to the remote upstream services: this way remote upstream services can use the tenant value and consider it safe to use to query/update data (with this hypothesis that only the Gateway can access the services, and of course there is not security...)

The example is composed of:

• The HTTP Gateway class: SampleCustomClientDimension
• The configuration file custom-client-dimension.conf
• The integration test class (with a mock server): SampleCustomClientDimensionTest

Custom routing

This example shows how to implement custom routing based on a custom dimension added to a client:

• Clients shares a common routing
• Depending on the custom dimension, here customer-a or customer-b, other routes available are different, and for the same path on the Gateway, different remote services are queried

The example is composed of:

• The HTTP Gateway class: SampleCustomRouting
• The configuration file custom-routing.conf
• The integration test class (with a mock server): SampleCustomRoutingTest

Header forwarding using config

A common use case is to forward some headers from downstream requests to upstream services. This can be done easily. For example: In the config file, define the headers to be forwarded:

http-gateway = {
    // ...
    headers-to-forward = ["Cookie", "X-Custom-Header"]
    // ...
}

In the API Gateway client, custom config values can be read using the configLoader object (or directly the config object if available): configLoader.getHttpGatewayConfig().getStringList("headers-to-forward")

So the complete request call will be written this way:

HttpGatewayPeekingUpstreamRequest<String, String> remoteRequest = httpGatewayUpstreamClient
    .prepareRequest(downstreamRequest)
    .withUrl(destinationService.getDestinationRoute().getDestinationUrl())
    .with(remoteServiceAuthenticator.forRoute(
    destinationService.getServiceId(), destinationService.getDestinationRoute().getRouteId()
    ))
    .copyBasicHeaders()
    // Forward config based headers
    .copyHeaders(configLoader.getHttpGatewayConfig().getStringList("headers-to-forward").toArray(String[]::new))
    .copyQueryParams();