FileRuleRuntime.java :  » Rule-Engine » hammurapi-rules » biz » hammurapi » rules » jsr94 » Java Open Source

package biz.hammurapi.rules.jsr94;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.rules.RuleExecutionSetNotFoundException;
import javax.rules.RuleSession;
import javax.rules.RuleSessionCreateException;
import javax.rules.RuleSessionTypeUnsupportedException;

import biz.hammurapi.config.ConfigurationException;
import biz.hammurapi.config.Context;
import biz.hammurapi.config.DomConfigFactory;
import biz.hammurapi.rules.jsr94.FileRuleServiceProvider.Registration;
import biz.hammurapi.util.Attributable;


/**
 * Loads rules from configuration file.
 * @author Pavel Vlasov
 * @revision $Revision$
 */
class FileRuleRuntime implements javax.rules.RuleRuntime {

  /**
   * 
   */
  private static final long serialVersionUID = 7086685393129078091L;
  private Map registrations;

  /**
   * Constructs rule runtime from registrations.
   */
  FileRuleRuntime(Map registrations) {
    this.registrations=registrations;
  }

  /**
   * Creates rule session.
   * @param uri Registration name for rule set. If uri starts with <code>direct:</code> then the rest is treated as direct URI of rule set definition.
   * If URI tail starts with <code>resource:</code> then rule set definition is loaded from classloader resource, otherwise it is loaded from URL.
   * If URI tails starts with <code>property:</code> then rule set is read from a property. Property value can be of type InputStream, Reader, org.w3c.Element, String, File or URL.
   * @param properties Vendor-specific properties.
   * @param type Session type.
   */
  public RuleSession createRuleSession(String uri, Map properties, int type)
      throws RuleSessionTypeUnsupportedException,
      RuleSessionCreateException, RuleExecutionSetNotFoundException {
    
    DomConfigFactory factory=new DomConfigFactory();
    Object container;
    
    try {
      if (uri==null) {
        throw new NullPointerException("URI is null");
      } else if (uri.startsWith("direct:")) {
        String ss=uri.substring("direct:".length());
        if (ss.startsWith("resource:")) {
          container=factory.create(getClass().getClassLoader().getResourceAsStream(ss.substring("resource:".length())), null);
        } else {
          container=factory.create(new URL(ss), null);
        }
      } else synchronized (registrations) {
        FileRuleServiceProvider.Registration registration=(Registration) registrations.get(uri);
        if (registration==null) {
          throw new RuleExecutionSetNotFoundException("Rule execution set is not found for URI: "+uri);
        }
        
        if (registration.getRef()!=null) {
          if (registration.getRef().startsWith("resource:")) {
            container=factory.create(getClass().getClassLoader().getResourceAsStream(registration.getRef().substring("resource:".length())), null);
          } else {
            container=factory.create(new URL(registration.getRef()), null);
          }
        } else if (registration.getValue()!=null) {
          try {
            container=factory.create(registration.getValue());
          } catch (ConfigurationException e) {
            throw new RuleSessionCreateException("Could instantiate rule set: "+e, e);
          }
        } else {
          throw new RuleSessionCreateException("Could instantiate rule set because neither reference nor definition is specified for URI: "+uri);        
        }
        
        if (registration.getProperties()!=null) {
          setAttributes(registration.getProperties(), container);
        }
      }    
    } catch (ConfigurationException e) {
      throw new RuleSessionCreateException("Could instantiate rule set: "+e, e);
    } catch (MalformedURLException e) {
      throw new RuleSessionCreateException("Malformed rule set URL: "+e, e);
    } catch (IOException e) {
      throw new RuleSessionCreateException("Could load rule set: "+e, e);
    }
    
    setAttributes(properties, container);
    biz.hammurapi.rules.jsr94.RuleSession ret = new biz.hammurapi.rules.jsr94.RuleSession((Context) container, type, uri);
    
    // Injecting rule session into container as "*" attribute, which will be addressable as "/@*"
    if (container instanceof Attributable) {
      ((Attributable) container).setAttribute("*", ret);
    }
    return ret;

  }

  private void setAttributes(Map properties, Object container) throws RuleSessionCreateException {
    if (properties!=null && !properties.isEmpty()) {
      if (container instanceof Attributable) {
        Iterator it=properties.entrySet().iterator();
        while (it.hasNext()) {
          Map.Entry entry=(Entry) it.next();
          ((Attributable) container).setAttribute(entry.getKey(), entry.getValue());
        }
      } else {
        throw new RuleSessionCreateException(container.getClass().getName()+" must implement "+Attributable.class);
      }
    }
  }

  /**
   * Returns list of registrations.
   */
  public List getRegistrations() {
    return new ArrayList(registrations.keySet());
  }

}