Example 8.29 Implementing Value List Handler Pattern

package corepatterns.apps.psa.handlers;

import java.util.*;
import corepatterns.apps.psa.dao.*;
import corepatterns.apps.psa.util.*;
import corepatterns.apps.psa.core.*;

public class ProjectListHandler 
extends ValueListHandler {

  private ProjectDAO dao = null;
  // use ProjectVO as a template to determine
  // search criteria
  private ProjectVO projectCriteria = null;

  // Client creates a ProjectVO instance, sets the 
  // values to use for search criteria and passes 
  // the ProjectVO instance as projectCriteria
  // to the constructor and to setCriteria() method
  public ProjectListHandler(ProjectVO projectCriteria) 
  throws ProjectException, ListHandlerException {
    try {
      this.projectCriteria = projectCriteria;
      this.dao = PSADAOFactory.getProjectDAO();
      executeSearch();
    } catch (Exception e) {
      // Handle exception, throw ListHandlerException
    }
  }

  public void setCriteria(ProjectVO projectCriteria) {
    this.projectCriteria = projectCriteria;
  }

  // executes search. Client can invoke this
  // provided that the search criteria has been
  // properly set. Used to perform search to refresh
  // the list with the latest data.
  public void executeSearch()   
  throws ListHandlerException {
    try {
      if (projectCriteria == null) {
        throw new ListHandlerException(
          "Project Criteria required...");
      }
      List resultsList = 
        dao.executeSelect(projectCriteria);        
      setList(resultsList);
    } catch (Exception e) {
      // Handle exception, throw ListHandlerException
    }
  }
}