:jbake-type: page
:jbake-status: published

= Apache Tamaya - Extension: Remote Configuration

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[[Remote]]
== Tamaya Remote Configuration (Extension Module)

Tamaya _Remote_ is an extension module. Refer to the link:../extensions.html[extensions documentation] for further details.


=== What functionality this module provides ?

Tamaya _Remote_ provides support for reading configuration from remote resources. It provides
out-of-the-box support for reading scoped configuration from a Tamaya configuration server as
provided with the Tamaya _server_ module .


=== Compatibility

The module is based on Java 7, so it will not run on Java 7 and beyond.


=== Installation

To use remote support you only must add the corresponding dependency to your module:

[source, xml, subs=attributes+]
-----------------------------------------------
<dependency>
  <groupId>org.apache.tamaya.ext</groupId>
  <artifactId>tamaya-remote</artifactId>
  <version>{tamaya_version}</version>
</dependency>
-----------------------------------------------


=== Reading Remote configuration from a Tamaya Configuration Server

The remote module allows reading JSON formatted configuration as provided by the Tamaya _server_ extension . The JSON
format used looks as follows:

[source, json]
-----------------------------------------------
{
  "java.vendor.url": "http://java.oracle.com/",
  "java.vendor.url.bug": "http://bugreport.sun.com/bugreport/",
  "java.vm.info": "mixed mode",
  "java.vm.name": "Java HotSpot(TM) 64-Bit Server VM",
  "java.vm.specification.name": "Java Virtual Machine Specification",
  "java.vm.specification.vendor": "Oracle Corporation",
  "java.vm.specification.version": "1.8",
  "java.vm.vendor": "Oracle Corporation",
  "java.vm.version": "25.45-b02",
  "sun.arch.data.model": "64",
  "sun.boot.class.path": "C:\apps\jdk18\jre\lib\resources.jar;C:\apps\jdk18\jre\lib\rt.jar;C:\apps\jdk18\jre\lib\sunrsasign.jar;C:\apps\jdk18\jre\lib\jsse.jar;C:\apps\jdk18\jre\lib\jce.jar;C:\apps\jdk18\jre\lib\charsets.jar;C:\apps\jdk18\jre\lib\jfr.jar;C:\apps\jdk18\jre\classes",
  "sun.boot.library.path": "C:\apps\jdk18\jre\bin",
  "sun.cpu.endian": "little",
  "sun.cpu.isalist": "amd64",
  "sun.desktop": "windows",
  "sun.io.unicode.encoding": "UnicodeLittle",
  "sun.java.command": "com.intellij.rt.execution.application.AppMain org.apache.tamaya.examples.remote.server.Start",
  "sun.java.launcher": "SUN_STANDARD",
  "sun.jnu.encoding": "Cp1252",
  "sun.management.compiler": "HotSpot 64-Bit Tiered Compilers",
  "sun.os.patch.level": "",
  "_class": "org.apache.tamaya.functions.FilteredConfiguration",
  "_info.filter": "java.v,sun",
  "_info.format": "application/json",
  "_info.timestamp": "1441463200571",
  "_timestamp": "1441463200571",
  "_type": "Configuration"
}
-----------------------------------------------

Basically there are no constraints about they keys provided. By default Tamaya uses keys prefixed with
+'_'+ to identify meta-data entries, but this is not a required precondition.

Finally such a remote configuration can be easily integrated by inheriting from the provided base
class. Hereby a default ordinal must be defined and the +protected Collection<URL> getAccessURLs()+
method must be implemented to define the URL from where the configuration should be accessible. Hereby
multiple URLs can be provided, which are accesed in order as provided by the collection's iterator. The
first accessible URL determines the configuration read.

[source, java]
-----------------------------------------------
public class RemotePropertySource extends BaseRemotePropertySource{

    @Override
    protected Collection<URL> getAccessURLs() {
        try {
            String configServerUrl = System.getenv("CONFIG_SERVER");
            if(configServerUrl==null){
                configServerUrl = System.getProperty("configServer");
            }
            if(configServerUrl==null){
                configServerUrl = "http://localhost:8888/config?scope=CLIENT&scopeId={clientId}&format=application/json";
            }
            System.out.println("Reading config from " + configServerUrl.replace("{clientId}", Client.getClientId()));
            return Arrays.asList(new URL[]{new URL(configServerUrl.replace("{clientId}", Client.getClientId()))});
        } catch (MalformedURLException e) {
            Logger.getLogger(getClass().getName()).log(Level.WARNING, "Failed to configure remote config location,", e);
            return Collections.emptySet();
        }
    }

}
-----------------------------------------------