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I have a legacy service that is running on-prem and have built a new service that runs on cloud which provides the same functionality. I have another java (spring) service which consumes the on-prem service. There are number of apis exposed by this on-prem service which is being called in multiple places within the consuming app. In order to prepare for migration to new service which provides the exact set of apis , I have defined a external toggle (using spring cloud config server). In order to flip the traffic from legacy to cloud endpoint , all I need to do is update the flag in the property file.

I currently have a service locator which has a resttemplate that makes a call to the legacy endpoint. While calling the cloud endpoint , I need to update different set of header values. Is there any java design pattern that I can leverage to make a call to cloud endpoint?

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1 Answer 1

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You can achieve this approach by mixing Strategy Pattern and Command Pattern.

You can define class(es) for service method(s), a class for service proxy, a class for configuration and a class to make a service call.

Define an interface for your service methods:

public interface IServiceMethod {
    void setClient(Service service);

    Object execute();

}

Create classes for your service methods:

public class SomeMethod implements IServiceMethod {

    private Service service;

    public SomeMethod() {
    }

    @Override
    public void setClient(Service service) {
        this.client = client;

    }

    @Override
    public T execute() {
        return client.getService().someMethod();

    }
}

Define a configuration class:

public class ServiceConfiguration {
    private String endPointUrl;
    private EnvironmentType envType; //DEV,TEST,PROD
    private String userName;
    private String password;
    private boolean isActive;
}

Define a class to wrap service and its configuration:

public interface IServiceProxy {

    Service getService();

    ServiceConfiguration getConfiguration();
}

Construct your service proxy with configuration and get endpoint (and other needed configuration data) from some provider:

public class ServiceProxy implements IServiceProxy {
    private Service service;
    private ServiceConfiguration configuration;

    public ServiceProxy(ServiceConfiguration serviceConfiguration) {
        this.service = someFactory.getInstance().getClient(serviceConfiguration);
        this.serviceConfiguration = serviceConfiguration;
    }

    @Override
    public Service getService() {
        return service;
    }

    @Override
    public ServiceConfiguration getConfiguration() {
        return configuration;
    }
}

Construct MethodExecutor with method:

public class MethodExecutor{
    private IServiceMethod iServiceMethod;

    public MethodExecutor(IServiceMethod iServiceMethod) {
        this.iServiceMethod = iServiceMethod;
    }

    public Object execute() {
        return iServiceMethod.execute();
    }
}

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