jtdaostrategy.java

来自「Java Pattern Oriented Framework (Jt) 是为了」· Java 代码 · 共 140 行

package Jt.DAO;

import Jt.JtFactory;
import Jt.JtMessage;
import Jt.JtObject;
import Jt.JtStrategy;


/**
 * DAO Strategy. This class is based on the Strategy design pattern.
 * Several DAO strategies are available: a) a native DAO implementation
 * based on the JDBC adapter. b) a Hibernate strategy.
 * Additional DAO strategies can be used in conjuntion with this class.
 *  
 */

public class JtDAOStrategy extends JtStrategy {


  public static final String JtCLASS_NAME = JtDAOStrategy.class.getName(); 
  private static final long serialVersionUID = 1L; 
  private String concreteStrategyClassName = JtDAOAdapter.JtCLASS_NAME;
  private boolean initted = false;
  private JtFactory factory = new JtFactory (); 

  public JtDAOStrategy () {
  }



  public String getConcreteStrategyClassName() {
      return concreteStrategyClassName;
  }



  public void setConcreteStrategyClassName(String concreteStrategyClassName) {
      this.concreteStrategyClassName = concreteStrategyClassName;
  }

  // Propagate Exceptions
  
  private Exception propagateException (Object obj)
  {
      Exception ex;

      if (obj == null)
          return null;

     
      ex = (Exception) factory.getValue(obj, "objException");

      if (ex != null)
          //setValue (this, "objException", ex);
          this.setObjException(ex);

      return (ex);
  }
  
  private void initialize () {

      JtFactory factory = new JtFactory ();

      if (concreteStrategy == null) {
          //    handleError ("processMessage: concreteStrategy attribute must be set");
          //    return (null);
          if (concreteStrategyClassName == null) {
              handleError ("processMessage: concreteStrategyClassName attribute must be set");   
              return;
          }
          concreteStrategy = factory.createObject(concreteStrategyClassName);
      }     
      
  }


  /**
   * Process object messages.
   * <ul>
   * </ul>
   */

  public Object processMessage (Object message) {

      String msgid = null;
      JtMessage e = (JtMessage) message;
      JtFactory factory = new JtFactory ();
      Object reply;
      

      if (e == null)
          return null;

      msgid = (String) e.getMsgId ();

      if (msgid == null)
          return null;

      //content = e.getMsgContent();
      //data = e.getMsgData ();
      if (!initted) {
          initialize ();     
          initted = true;
      }
      
      if (msgid.equals (JtObject.JtINITIALIZE)) {
          if (!initted) {
              initialize ();     
              initted = true;
          }
          return null;     
      }
           
      
      if (msgid.equals (JtDAOAdapter.JtREAD_MAPPING_STREAM)) {
          
          // Ignore JtDAOAdapter.JtREAD_MAPPING_STREAM unless the concrete
          // strategy is the default strategy (JtDAOAdapter)
          if (!JtDAOAdapter.JtCLASS_NAME.equals(concreteStrategyClassName))
              return (null);    
      }

      // Let the concrete strategy process the message
      
      reply = super.processMessage (message);
      
      if (concreteStrategy != null) {
          propagateException (concreteStrategy);  
      }
      
      return (reply);

  }
  
}