syncsessionbankservlet.java

来自「JAVA Servlet2.3外文书籍源码」· Java 代码 · 共 140 行

JAVA

140 行

package synchronization;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import java.util.Enumeration;
import java.util.Vector;
import java.util.Hashtable;

public class SyncSessionBankServlet extends HttpServlet
{
  private ServletContext servletContext=null;

  public void init(ServletConfig config) throws ServletException
  {
    super.init(config);
    this.servletContext=config.getServletContext();
    resetValues(null);
  } 

  public void init() throws ServletException
  {
    //resetValues(null);
  } 

  public void doGet (HttpServletRequest req, HttpServletResponse res)
                      throws ServletException, IOException
  {
    InOut.in();

    String reset = req.getParameter("reset");

    String fromAccount = req.getParameter("from");
    String toAccount = req.getParameter("to");
    String amount = req.getParameter("amount");

    PrintWriter writer = res.getWriter();
    writer.println("<html><head></head>");
    writer.println("<body style=\"font-family:verdana;font-size:8pt\">");

    // -- Reset the values --
    if (reset!=null)
      resetValues(req);

    if ( (fromAccount!=null)
         && (toAccount!=null)
         && (amount!=null)
       )
    {
      // -- A money transfer --
      transfer(fromAccount, toAccount, amount, req);
    }

    showData(writer, req);

    writer.println("</body></html>");
    writer.close();

    InOut.out();
  }

  public void resetValues(HttpServletRequest req) throws ServletException
  {
    Hashtable accounts=(Hashtable) servletContext.getAttribute("accounts");    
    if (accounts==null) accounts=new Hashtable();    

    accounts.put("000001","1000");
    accounts.put("000002","1000");

    servletContext.setAttribute("accounts",accounts);

    if (req==null) return;

    HttpSession session=req.getSession(true);
    Vector userTransactions=new Vector();
    session.setAttribute("transactions",userTransactions);
  } 

  private void showData(PrintWriter writer, HttpServletRequest req)
  {
    // -- show account balances --

    Hashtable accounts=(Hashtable) servletContext.getAttribute("accounts");
    if (accounts==null) return;    

    writer.println("<b>Account Balances</b><br><br>");

    for (Enumeration keys=accounts.keys(); keys.hasMoreElements(); )
    {
      String thisKey=(String) keys.nextElement();
      String thisBalance=(String) accounts.get(thisKey);
      writer.println("Account "+thisKey+" has balance "+thisBalance+"<br>");
    } 

    // -- show user transactions reversed --
    HttpSession session=req.getSession(true);
    Vector userTransactions=(Vector) session.getAttribute("transactions");
    if (userTransactions==null) return;

    writer.println("<br><b>User Transactions</b><br><br>");

    int i=userTransactions.size()-1;

    if (i>=0) writer.println("<b>"+userTransactions.elementAt(i)+"</b><br>"); 

    while (--i>=0)
    {
      writer.println(""+userTransactions.elementAt(i)+"<br>");
    }
  }

  private synchronized void transfer(String fromAccount, String toAccount, String amount, HttpServletRequest req)
  {
    Hashtable accounts=(Hashtable) servletContext.getAttribute("accounts");
    if (accounts==null) return;    

    int fromAccountBalance=new Integer((String)accounts.get(fromAccount)).intValue();
    int newFromAccountBalance=fromAccountBalance-(new Integer(amount).intValue());

    int toAccountBalance=new Integer((String)accounts.get(toAccount)).intValue();
    int newToAccountBalance=toAccountBalance+(new Integer(amount).intValue());

    try {Thread.sleep(5000);} catch (java.lang.InterruptedException ex) {}

    accounts.put(fromAccount,""+newFromAccountBalance);
    accounts.put(toAccount,""+newToAccountBalance);

    servletContext.setAttribute("accounts",accounts);

    HttpSession session=req.getSession(true);
    Vector userTransactions=(Vector) session.getAttribute("transactions");
    if (userTransactions==null) userTransactions=new Vector();

    String transaction="Transfer of "+amount+" from account "+fromAccount+" to account "+toAccount;
    userTransactions.add(transaction);
    session.setAttribute("transactions",userTransactions);
  }
}

syncsessionbankservlet.java - 源码说明

本页面展示了「JAVA Servlet2.3外文书籍源码」中的 syncsessionbankservlet.java 源码文件，采用 Java 编程语言编写，共 140 行代码。您可以在线阅读完整代码内容，也可以返回资源详情页下载完整源码包进行本地学习和开发。

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