I. Prerequisite

I.I Requirements

• Java: 1.7+

I.II Mandatory Setup

Apollo client requires AppId and Environment information available to function properly, so please read the following and configure them properly:

1. AppId

AppId is the identity for the application, which is a key information to retrieve the config from server.

AppId information should be put in classpath:/META-INF/app.properties with its key as app.id.

For example, you could place the file as the following screenshot:

And config the file as:

app.id=YOUR-APP-ID

2. Environment

Apollo supports config by multiple environments, so environment is another key information to retrieve the config from server.

Environment could be configured in 3 ways:

1. As Java System Property

   • You could specify environment as java system property env
   • For example, when starting the java application, it can be configured via -Denv=YOUR-ENVIRONMENT
   • Please note the key should be lower case

2. As OS System Environment

   • You could also specify environment as system environment ENV
   • Please note the key should be UPPER CASE

3. As Property File

   • You could create a file /opt/settings/server.properties on the target machine
   • And specify the environment in the file as env=YOUR-ENVIRONMENT
   • Please note the key should be lower case

Currently, env allows the following values (case-insensitive):

• DEV
• FWS
• FAT
• UAT
• PRO

I.III Optional Setup

Cluster

Apollo supports config separated by clusters, which means for one appId and one environment, you could have different configs.

If you need this functionality, you could specify the cluster as follows:

1. As Java System Property
   • You could specify cluster as java system property apollo.cluster
   • For example, when starting the java application, it can be configured via -Dapollo.cluster=xxx
   • Please note the key should be lower case
2. As Property file
   • You could create a file /opt/settings/server.properties on the target machine
   • And specify the idc cluster in the file as idc=xxx
   • Please note the key should be lower case

Cluster Precedence

1. If both apollo.cluster and idc are specified:

   • We will first try to load config from cluster specified as apollo.cluster
   • If not found, we will fall back to cluster specified as idc
   • If still not found, we will fall back to the default cluster default

2. If only apollo.cluster is specified:

   • We will first try to load config from cluster specified as apollo.cluster
   • If not found, we will fall back to the default cluster default

3. If only idc is specified:

   • We will first try to load config from cluster specified as idc
   • If not found, we will fall back to the default cluster default

4. If neither apollo.cluster nor idc is specified:

   • We will load config from the default cluster default

II. Maven Dependency

	<dependency>
		<groupId>com.ctrip.framework.apollo</groupId>
		<artifactId>apollo-client</artifactId>
		<version>0.8.0</version>
	</dependency>

III. Client Usage

1. Load config from default namespace(application)

Config config = ConfigService.getAppConfig();
String someKey = "someKeyFromDefaultNamespace";
String someDefaultValue = "someDefaultValueForTheKey";
System.out.println(String.format("Value for key %s is %s", someKey, config.getProperty(someKey, someDefaultValue)));

2. Register config change listener

Config config = ConfigService.getAppConfig();
config.addChangeListener(new ConfigChangeListener() {
	@Override
	public void onChange(ConfigChangeEvent changeEvent) {
		System.out.println("Changes for namespace " + changeEvent.getNamespace());
		for (String key : changeEvent.changedKeys()) {
			ConfigChange change = changeEvent.getChange(key);
			System.out.println(String.format("Found change - key: %s, oldValue: %s, newValue: %s, changeType: %s", change.getPropertyName(), change.getOldValue(), change.getNewValue(), change.getChangeType()));
		}
	}
});

3. Load config from public namespace

String somePublicNamespace = "CAT";
Config config = ConfigService.getConfig(somePublicNamespace);
String someKey = "someKeyFromPublicNamespace";
String someDefaultValue = "someDefaultValueForTheKey";
System.out.println(String.format("Value for key %s is %s", someKey, config.getProperty(someKey, someDefaultValue)));