JBoss AS 7 application specific properties file

Question

I have several independent Java EE modules (WAR web applications, and JAR EJB modules) which I deploy on JBoss 7.1.1 AS. I want to:

1. Centralize configuration of these modules in one *.properties file.
2. Make this file available in classpath.
3. Keep the installation/configuration of this file as simple as possible. Ideally would be just to put it in some JBoss folder like: ${JBOSS_HOME}/standalone/configuration.
4. Make changes to this file available without restarting the application server.

Is this possible?

I already found this link: How to put an external file in the classpath, which explains that preferable way to do this is to make static JBoss module. But, I have to make dependency to this static module in every application module that I deploy, which is a kind of coupling I'm trying to avoid.

Answer 1

Maybe a simple solution is to read the file from a singleton or static class.

private static final String CONFIG_DIR_PROPERTY = "jboss.server.config.dir"; 

private static final String PROPERTIES_FILE = "application-xxx.properties";

private static final Properties PROPERTIES = new Properties();

static {
    String path = System.getProperty(CONFIG_DIR_PROPERTY) + File.separator + PROPERTIES_FILE;  
    try {  
        PROPERTIES.load(new FileInputStream(path));
    } catch (MalformedURLException e) {
       //TODO 
    } catch (IOException e) {
       //TODO
    } 
}

Answer 2

Here is a full example using just CDI, taken from this site.

This configuration will also work for JBoss AS7.

1. Create and populate a properties file inside the WildFly configuration folder

   $ echo 'docs.dir=/var/documents' >> .standalone/configuration/application.properties
   

2. Add a system property to the WildFly configuration file.

   $ ./bin/jboss-cli.sh --connect
   [standalone@localhost:9990 /] /system-property=application.properties:add(value=${jboss.server.config.dir}/application.properties)
   

This will add the following to your server configuration file (standalone.xml or domain.xml):

<system-properties>
    <property name="application.properties" value="${jboss.server.config.dir}/application.properties"/>
</system-properties>

3. Create the singleton session bean that loads and stores the application wide properties

   import java.io.File;
   import java.io.FileInputStream;
   import java.io.IOException;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.Properties;
   
   import javax.annotation.PostConstruct;
   import javax.ejb.Singleton;
   
   @Singleton
   public class PropertyFileResolver {
   
       private Logger logger = Logger.getLogger(PropertyFileResolver.class);
       private String properties = new HashMap<>();
   
       @PostConstruct
       private void init() throws IOException {
   
           //matches the property name as defined in the system-properties element in WildFly
           String propertyFile = System.getProperty("application.properties");
           File file = new File(propertyFile);
           Properties properties = new Properties();
   
           try {
               properties.load(new FileInputStream(file));
           } catch (IOException e) {
               logger.error("Unable to load properties file", e);
           }
   
           HashMap hashMap = new HashMap<>(properties);
           this.properties.putAll(hashMap);
       }
   
       public String getProperty(String key) {
           return properties.get(key);
       }
   }
   

4. Create the CDI Qualifier. We will use this annotation on the Java variables we wish to inject into.

   import java.lang.annotation.ElementType;
   import java.lang.annotation.Retention;
   import java.lang.annotation.RetentionPolicy;
   import java.lang.annotation.Target;
   
   import javax.inject.Qualifier;
   
   @Qualifier
   @Retention(RetentionPolicy.RUNTIME)
   @Target({ ElementType.METHOD, ElementType.FIELD, ElementType.CONSTRUCTOR })
   public @interface ApplicationProperty {
   
       // no default meaning a value is mandatory
       @Nonbinding
       String name();
   }
   

5. Create the producer method; this generates the object to be injected

   import javax.enterprise.inject.Produces;
   import javax.enterprise.inject.spi.InjectionPoint;
   import javax.inject.Inject;
   
   public class ApplicationPropertyProducer {
   
       @Inject
       private PropertyFileResolver fileResolver;
   
       @Produces
       @ApplicationProperty(name = "")
       public String getPropertyAsString(InjectionPoint injectionPoint) {
   
           String propertyName = injectionPoint.getAnnotated().getAnnotation(ApplicationProperty.class).name();
           String value = fileResolver.getProperty(propertyName);
   
           if (value == null || propertyName.trim().length() == 0) {
               throw new IllegalArgumentException("No property found with name " + value);
           }
           return value;
       }
   
       @Produces
       @ApplicationProperty(name="")
       public Integer getPropertyAsInteger(InjectionPoint injectionPoint) {
   
           String value = getPropertyAsString(injectionPoint);
           return value == null ? null : Integer.valueOf(value);
       }
   }
   

6. Lastly inject the property into one of your CDI beans

   import javax.ejb.Stateless;
   import javax.inject.Inject;
   
   @Stateless
   public class MySimpleEJB {
   
       @Inject
       @ApplicationProperty(name = "docs.dir")
       private String myProperty;
   
       public String getProperty() {
           return myProperty;
       }
   }