spring-cloud-core

#Spring Cloud Core

This core library provides programmatic access to application and service information. This library has no Spring dependencies and may be used in non-Spring applications.

This library requires Java 6 or newer.

This library is cloud-agnostic. Using Java SPI, it supports pluggable cloud and service connectors; support for Cloud Foundry and Heroku is available out-of-the-box, in addition to locally-provided configuration for development and testing.

##Connecting to a cloud

Note: If you are using Spring Cloud in a Spring application, you should consider automatically injecting Spring beans instead.

• Include the desired cloud connectors on the runtime classpath as described in the main documentation.

• Create a CloudFactory instance. Creation of a CloudFactory instance is a bit expensive, so using a singleton instance is recommended. If you are using a dependency injection framework such as Spring, create a bean for the CloudFactory.

CloudFactory cloudFactory = new CloudFactory(); ```

• Obtain the Cloud object for the environment in which the application is running.

Cloud cloud = cloudFactory.getCloud(); ``` Note that you must have a CloudConnector suitable for your deployment environment on your classpath. For example, if you are deploying the application to Cloud Foundry, you must add cloudfoundry-connector to your classpath. If no suitable `CloudConnctor` is found, the `getCloud()` method will throw a `CloudException`.

• Use the Cloud instance to access application and service information and to create service connectors.

// ServiceInfo has all the information necessary to connect to the underlying service List serviceInfos = cloud.getServiceInfos(); ```

```java

// find the ServiceInfo definitions suitable for connecting to a particular service type List databaseInfos = cloud.getServiceInfos(DataSource.class); ````

```java

// Alternately, let Spring Cloud create a service connector for you String serviceId = "inventory-db"; DataSource ds = cloud.getServiceConnector(serviceId, DataSource.class, null /* default config */); ```

##Adding cloud connectors

A cloud provider may extend Spring Cloud by adding a new CloudConnector to make Spring Cloud work with a new cloud platform. The connector is responsible for telling whether the application is running in the specific cloud, identifying application information (such as the name and instance ID of the particular running instance), and mapping bound services (such as URIs exposed in environment variables) as ServiceInfo objects.

See the Cloud Foundry and Heroku connectors for examples.

Spring Cloud uses the Java SPI to discover available connectors. New cloud connectors should list the fully-qualified class name in the provider-configuration file at

META-INF/services/org.springframework.cloud.CloudConnector

Adding service discovery

To allow Spring Cloud to discover a new type of service (HelloWorldService), create a ServiceInfo class containing the information necessary to connect to your service. If your service can be specified via a URI, extend UriBasedServiceInfo and provide the URI scheme in a call to the super constructor.

This class will expose information for a service available at

helloworld://username:password@host:port/Bonjour

public class HelloWorldServiceInfo extends UriBasedServiceInfo {
    public static final String URI_SCHEME = "helloworld";

	// needed to support structured service definitions like Cloud Foundry
    public HelloWorldServiceInfo(String id, String host, int port, String username, String password, String greeting) {
		super(id, URI_SCHEME, host, port, username, password, greeting);
    }

    // needed to support URI-based service definitions like Heroku
    public HelloWorldServiceInfo(String id, String uri) {
        super(id, uri);
    }
}

Then you will need to create a ServiceInfoCreator for each cloud platform you want to support. You will probably want to extend the appropriate creator base class(es), such as HerokuServiceInfoCreator. This is often as simple as writing a method that instantiates a new HelloWorldServiceInfo.

Register your ServiceInfoCreator classes in the appropriate provider-configuration file for your cloud's ServiceInfoCreator base class.

Adding service connectors

A service connector consumes a ServiceInfo discovered by the cloud connector and converts it into the appropriate service object, such as a DataSource for a service definition representing a SQL database.

Service connectors may be tightly bound to the framework whose service objects they are creating; for example, some connectors in the Spring service connector create connection factories defined by Spring Data, for use in building Spring Data templates.

To add new service connectors, implement ServiceConnectorCreator in your connector classes and list the fully-qualified class names in the provider-configuration file at

META-INF/services/org.springframework.cloud.service.ServiceConnectorCreator