traderbean.java

来自「java的一系列产品中包括jsme,jmse,j2ee,本文件提供j2ee实现的」· Java 代码 · 共 124 行

package stocktrader;

import javax.ejb.CreateException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class TraderBean implements SessionBean {

  static final boolean VERBOSE = true;
  private SessionContext ctx;
  private Context environment;
  private double tradingBalance;

  /**
   * Sets the session context.
   */
  public void setSessionContext(SessionContext ctx) {
    System.out.println("called setSessionContext()");
    this.ctx = ctx;
  }

  /**
   * This method is required by the EJB Specification,
   * but is not used by this example.
   *
   */
  public void ejbActivate() {
    System.out.println("called ejbActivate()");
  }

  /**
   * This method is required by the EJB Specification,
   * but is not used by this example.
   *
   */
  public void ejbPassivate() {
    System.out.println("called ejbPassivate()");
  }

  /**
   * This method is required by the EJB Specification,
   * but is not used by this example.
   *
   */
  public void ejbRemove() {
    System.out.println("called ejbRemove()");
  }

  /**
   * This method corresponds to the create method in the home interface
   * "TraderHome.java".
   * The parameter sets of the two methods are identical. 
   */
  public void ejbCreate() throws CreateException {
    System.out.println("called ejbCreate()");
    try {
      InitialContext ic = new InitialContext();
      environment = (Context) ic.lookup("java:comp/env");
    } catch (NamingException ne) {
      throw new CreateException("Could not look up context");
    }
    this.tradingBalance = 0.0;
  }

  /**
   * Buys shares of a stock for a named customer.
   */
  public TraderResult buy(String customerName, String stockSymbol, int shares)
    throws ProcessingErrorException
  {
    System.out.println("buy (" + customerName + ", " + stockSymbol + ", " + shares + ")");

    double price = getStockPrice(stockSymbol);
    tradingBalance -= (shares * price); // subtract purchases from cash account

    return new TraderResult(shares, price, TraderResult.BUY);
  }

  /**
   * Sells shares of a stock for a named customer.
   */
  public TraderResult sell(String customerName, String stockSymbol, int shares)
    throws ProcessingErrorException
  {
    System.out.println("sell (" + customerName + ", " + stockSymbol + ", " + shares + ")");

    double price = getStockPrice(stockSymbol);
    tradingBalance += (shares * price);

    return new TraderResult(shares, price, TraderResult.SELL);
  }

  /**
   * Returns the current balance of a trading session.
   */
  public double getBalance() {
    return tradingBalance;
  }

  /**
   * Returns the stock price for a given stock.
   */
  public double getStockPrice(String stockSymbol) 
    throws ProcessingErrorException 
  {
    try {
      return ((Double) environment.lookup(stockSymbol)).doubleValue();
    } catch (NamingException ne) {
      throw new ProcessingErrorException ("Stock symbol " + stockSymbol + 
                                          " does not exist");
    } catch (NumberFormatException nfe) {
      throw new ProcessingErrorException("Invalid price for stock "+stockSymbol);
    }
  }
}