5. Zookeeper Dependencies

Below the root property you have to represent each dependency has by an alias due to the constraints of Ribbon (the application id has to be placed in the URL thus you can’t pass any complex path like /foo/bar/name). The alias will be the name that you will use instead of serviceId for DiscoveryClient, Feign or RestTemplate.

In the aforementioned examples the aliases are newsletter and mailing. Example of Feign usage with newsletter would be:

@FeignClient("newsletter")
public interface NewsletterService {
        @RequestMapping(method = RequestMethod.GET, value = "/newsletter")
        String getNewsletters();
}

Represented by path yaml property.

Path is the path under which the dependency is registered under Zookeeper. Like presented before Ribbon operates on URLs thus this path is not compliant with its requirement. That is why Spring Cloud Zookeeper maps the alias to the proper path.

Represented by loadBalancerType yaml property.

If you know what kind of load balancing strategy has to be applied when calling this particular dependency then you can provide it in the yaml file and it will be automatically applied. You can choose one of the following load balancing strategies

Represented by contentTypeTemplate and version yaml property.

If you version your api via the Content-Type header then you don’t want to add this header to each of your requests. Also if you want to call a new version of the API you don’t want to roam around your code to bump up the API version. That’s why you can provide a contentTypeTemplate with a special $version placeholder. That placeholder will be filled by the value of the version yaml property. Let’s take a look at an example.

Having the following contentTypeTemplate:

application/vnd.newsletter.$version+json

and the following version:

v1

Will result in setting up of a Content-Type header for each request:

application/vnd.newsletter.v1+json

Represented by headers map in yaml

Sometimes each call to a dependency requires setting up of some default headers. In order not to do that in code you can set them up in the yaml file. Having the following headers section:

headers:
    Accept:
        - text/html
        - application/xhtml+xml
    Cache-Control:
        - no-cache

Results in adding the Accept and Cache-Control headers with appropriate list of values in your HTTP request.

Represented by required property in yaml

If one of your dependencies is required to be up and running when your application is booting then it’s enough to set up the required: true property in the yaml file.

If your application can’t localize the required dependency during boot time it will throw an exception and the Spring Context will fail to set up. In other words your application won’t be able to start if the required dependency is not registered in Zookeeper.

You can read more about Spring Cloud Zookeeper Presence Checker in the following sections.

You can provide a colon separated path to the JAR containing stubs of the dependency. Example

stubs: org.springframework:foo:stubs

means that for a particular dependencies can be found under:

This is actually equal to

stubs: org.springframework:foo

since stubs is the default classifier.