printermanager.java

ORACLE AQ sample 演示的如何出列

package oracle.otnsamples.AQ.Manager;

/**
 * @author  Anupama
 * @version 1.0
 *
 * Development Environment        :  Oracle9i JDeveloper
 * Name of the Application        :  PrinterManager.java
 * Creation/Modification History  :
 *
 *    Anupama      25-Jan-2002      Created
 *
 */

// Servlet imports
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

// Util imports
import java.util.Hashtable;
import java.util.Enumeration;

// Other files
import oracle.otnsamples.AQ.Helper.Product;
import oracle.otnsamples.AQ.Helper.ManufactureHelper;

/**
 * This class is called for any operation performed by the user who
 * logged in as Printer Manufacturer. Each method corresponds to one request
 * from the manufacturer. Each method retrieves the data required by the
 * Helper class either from the request/session and sends it to the Helper.
 * The data retrieved from the Helper is stored in request or session as per
 * the requirement.
 */
public class PrinterManager implements Manager {

  /**
   * SessionName to stores the session variable.
   */
  HttpSession m_session;

  /**
   * Stores the user type who has logged in.
   */
  String m_userType="";

  /**
   * Empty Constructor.
   */
  public PrinterManager(){
  }

  /**
   * This method is called after the manufacturer logged in successfully.
   * The basic functionality of this method is to get the parameters from
   * session, call the corresponding method in Helper to retrieve the
   * products the manufacturer
   * has from the database and stores them in session.
   *
   * @param p_request Holds the request object
   * @exception Exception Incase of some error or unreported Exception
   * @see ManufactureHelper.java
   */
  public void displayProducts(HttpServletRequest p_request) throws Exception {
    // Retrieves the parameters present in request
    setParameters(p_request);

    // Retrieve the details of the products the manufacture has in the form of
    // a hash table and store it in session.
    m_session.setAttribute("ProductsList",
                              ManufactureHelper.displayProducts(m_userType));
  }

  /**
   * Empty method which is called when the manufacturer clicks on the Add button.
   * Nothing is done here and the manufacturer is redirected to the page
   * where he is asked to enter the details of the product to be added.
   *
   * @param p_request Holds the request object
   * @exception Exception Incase of some error or unreported Exception
   */
  public void addRequest(HttpServletRequest p_request) throws Exception {
  }

  /**
   * This method is called if the manufacturer wants to update a product
   * selected in the JSP page. the basic functionality of this method is to
   * get the parameter(s) from session, retrieve the details of the product
   * to be changed using the id of the product sent through request and send
   * the details of the product thus retrieved back through request.
   *
   * @param p_request Holds the request object
   * @exception Exception Incase of some error or unreported Exception
   * @see ManufactureHelper.java
   */
  public void updateRequest(HttpServletRequest p_request) throws Exception {
    // Retrieves the parameters present in request
    setParameters(p_request);

    // Retrieve the ids of all the products the manufacture selected for update.
    // Only one product id will be sent as only one product can be updated at
    // a time.(Javascript present in the page checks to see that only one
    // product is selected for update)
    String[] productIds = p_request.getParameterValues("ProductsToBeChanged");
    Product productObj  = new Product();

    // Get the details of all the products stored in session
    Hashtable productsList  = (Hashtable)m_session.getAttribute("ProductsList");

    // Retrieve the details of the product selected using its id.
    Enumeration enum  = productsList.keys();
    while(enum.hasMoreElements()){
       Object key = enum.nextElement();
       if(key.equals(productIds[0])){
         productObj = (Product)productsList.get(key);
         break;
       }
    }
    // Store the details of the product to be updated in request.
    p_request.setAttribute("UpdatePrdInfo",productObj);
  }

  /**
   * This method is called if the manufacturer wants to add a product.
   * The basic functionality of this method is to get the parameter(s)
   * from session, store the details of the product
   * entered in JSP page in database using the helper class and store the
   * hash table returned containing the list of all products present in
   * the database in session.
   *
   * @param p_request Holds the request object
   * @exception Exception Incase of some error or unreported Exception
   */
  public void addProduct(HttpServletRequest p_request) throws Exception {
    // Retrieves the parameters present in request
    setParameters(p_request);

    // Retrieves the details of the product from the JSP page in the form of
    // Product object.
    Product product = getProductDetails(p_request);

    // Calls the addProduct method present in Helper to add the product details
    // in the database. If the product is added successfully
    m_session.setAttribute("ProductsList",ManufactureHelper.addProduct(
         m_userType,(Hashtable)m_session.getAttribute("ProductsList"),product));

    infoSentToJSP("Add",product.getProductID(),p_request);
  }

  /**
   * This method is called if the manufacturer wants to update a product.
   * The basic functionality of this method is to get the parameter(s)
   * from session and the product details from
   * the JSP page and
   * stores them in Product object. It then sends the object
   * to the helper and stores the product list returned containing the
   * details of all the products including the updated product in session.
   *
   * @exception Exception Incase of some error or unreported Exception
   * @param p_request Holds the request object
   * @see ManufactureHelper.java
   * @see Product.java
   */
  public void updateProduct(HttpServletRequest p_request) throws Exception {
    // Retrieves the parameters present in request
    setParameters(p_request);

    // Gets the details of the product from JSP page using the method and stores
    // it in Product object.
    Product product = getProductDetails(p_request);

    // Send the details of all the products present along with the details of
    // the product to be updated to the Helper which updates it in the database
    // as well as in the hash table and returns the hash table back. Store
    // hash table in session.
    m_session.setAttribute("ProductsList",ManufactureHelper.updateProduct(
         m_userType,(Hashtable)m_session.getAttribute("ProductsList"),product));

    infoSentToJSP("Update",product.getProductID(),p_request);
  }

 /**
  * This method is called if the manufacturer wants to delete a product.
  * The basic functionality of this method is to gets the parameter(s)
  * from session. It then gets the details of all the products
  * selected for deletion from their product ids using the hash table in session
  * and sends them to Helper. At last it stores the product list returned
  * from the helper after deleting the products in database inside session.
  *
  * @exception Exception Incase of some error or unreported Exception
  * @param p_request Holds the request object
  * @see Product.java
  * @see ManufactureHelper.java
  */
 public void deleteProducts(HttpServletRequest p_request) throws Exception {
    // Retrieves the parameters present in request
    setParameters(p_request);

    // Retrieve the id of all products which are to be deleted.
    String[] productIds = p_request.getParameterValues("ProductsToBeChanged");
    int noOfPrds  = productIds.length;
    Product[] productsToBeDeleted = new Product[noOfPrds];

    // Retrieve the details of all those products using their product ids
    // from the product list present in session.
    for(int i=0;i<noOfPrds;i++){
      productsToBeDeleted[i]  = getProductDetailsFromHash(productIds[i]);
    }

    // Send the details of the product to be deleted to the helper and store
    // the returned updated product list in session.
    m_session.setAttribute("ProductsList",ManufactureHelper.deleteProducts(
           m_userType,(Hashtable)m_session.getAttribute("ProductsList"),
           productsToBeDeleted));

    infoSentToJSP("Delete",productIds,p_request);
  }

  /**
   * Gets the details of the product entered in the JSP page using the
   * request object and stores it in Product object.
   *
   * @param p_request Holds the request object
   * @exception Exception Incase of some error or unreported Exception
   * @return Complete product details got from request object
   */
  private Product getProductDetails(HttpServletRequest p_request)
                                            throws Exception{
   Product product  = new Product();

   // If the id of the product is present then retrieve it. This condition
   // is required because when a product is added its product id can't be
   // retrieved from the JSP page.
   if(p_request.getParameter("ProductId") != null){
     product.setProductID(p_request.getParameter("ProductId"));
   }

   product.setProductName(p_request.getParameter("ProductName"));

   // Get the manufacturerId from the Hash table present in session.
   // If no products are present in session then null is returned.
   product.setManufactureID(getManufacturerIDFromHash());
   product.setProductDesc(p_request.getParameter("ProductDesc"));
   product.setCategoryDesc(p_request.getParameter("CategoryDesc").trim());
   product.setProductPrice(p_request.getParameter("Price"));
   product.setQuantityOnHand(p_request.getParameter("Quantity"));
   return product;
  }

  /**
   * Retrieves the manufacturer id of the products. In this sample as the
   * database contains the products sold by only one manufacturer the
   * manufacturer id of the first product is retrieved and sent. If there are no
   * no products in hash table then null is returned.
   *
   * @exception Exception Incase of some error or unreported Exception
   * @return Manufacturer id of the products
   */
  private String getManufacturerIDFromHash() throws Exception{
   // Retrieve the details of all the products from session
   Hashtable productsList = null;

   // If no products are present in the hash table then return null
   if(m_session.getAttribute("ProductsList")==null){
     return null;
   }else{
     productsList = (Hashtable)m_session.getAttribute("ProductsList");
   }
      
   // If there are no products in hash table
   if(productsList.size()==0){
    return null;
   }else{
     Enumeration enum       = productsList.keys();
     Object key             = enum.nextElement();

     // Get the details of first product from the Hash
     Product product        = (Product)productsList.get(key);

     // Retrieve the manufacturer id of the first product. As the database
     // contains the products which only on manufacturer holds, the manufacturer
     // id can be got using manufacturer id of any product.
     return (product.getManufactureID());
    }
  }

  /**
   * Retrieves the session object and using that retrieves the
   * user type of the person logged in.
   *
   * @param p_request Holds the request object
   */
  private void setParameters(HttpServletRequest p_request){
    // Get the already existing session object.
    m_session  = p_request.getSession(false);

    // Retrieve the user type from session.
    m_userType = (String)m_session.getAttribute("User");
  }

  /**
   * Gets the details of the products from the product list stored in session
   * using the product id sent.
   *
   * @param p_productId Id of the product whose details are required.
   * @exception Exception Incase of some error or unreported Exception
   * @return Details of the product whose id is sent.
   */
  private Product getProductDetailsFromHash(String p_productId) throws Exception{
   // Get the details of all the products from the session.
   Hashtable productsList = (Hashtable)m_session.getAttribute("ProductsList");
   Enumeration enum       = productsList.keys();
   Product product        = new Product();
   while(enum.hasMoreElements()){
     Object key  =  enum.nextElement();

     // If the product id sent is equal to the product id present in the
     // list of products then store the product details.
     if(key.equals(p_productId)){
        product = (Product)productsList.get(key);
        break;
     }
    }
    return product;
  }

  /**
   * This method helps to send the data required by the JSP
   * out of the information sent to it. It stores the product
   * ID sent to it in an String array and forwards it to
   * the overloaded method.
   *
   * @exception Exception Incase of some error or unreported Exception
   * @param p_action Tells what action was performed
   * @param p_productId Id of the product whose details are changed.
   * @param p_request Holds the request object
   */
  private void infoSentToJSP(String p_action,String p_productId,
                            HttpServletRequest p_request) throws Exception{
   infoSentToJSP(p_action,new String[]{p_productId},p_request);
  }

  /**
   * This is an overloaded method. This method helps to send
   * the data required by the JSP out of the information sent to it.
   *
   * @exception Exception Incase of some error or unreported Exception
   * @param p_action Tells what action was performed
   * @param p_productIdsArr Id of all the products whose details are
   *     deleted.
   * @param p_request Holds the request object
   */
  private void infoSentToJSP(String p_action,String[] p_productIdsArr,
                              HttpServletRequest p_request) throws Exception{
    p_request.setAttribute("ProductIdArr",p_productIdsArr);
    p_request.setAttribute("Action",p_action);
  }
}