borrowbean.java

Java实现的图书管理系统

/*
 * BorrowBean.java
 *
 * Created on 2003年5月13日, 上午11:48
 */

/**
 *
 * @author  administrator
 */
import java.sql.*;
import javax.sql.*;
import java.util.*;
import java.math.*;
import javax.ejb.*;
import javax.naming.*;
import javax.rmi.PortableRemoteObject;
import java.rmi.RemoteException;

public class BorrowBean implements EntityBean{
    //entity variables
    private String id;
    private String userName;
    private String bookId;
    private String borrowDate;
    private String returned;
   
    //other variables
    private EntityContext context;
    private Connection con;
    private String dbName = "java:comp/env/jdbc/book";
    
    //entity bean's method
    public void ejbActivate() throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
        id = (String)context.getPrimaryKey();
    }
    
    public void ejbLoad() throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
        try {
         loadRow();
       } catch (Exception ex) {
           throw new EJBException("ejbLoad: " + 
              ex.getMessage());
       }
    }
    
    public void ejbPassivate() throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
        id = null;
    }
    
    //we don't use this method for this programm
    public void ejbRemove() throws javax.ejb.RemoveException, javax.ejb.EJBException, java.rmi.RemoteException 
    {
    }
    
    public void ejbStore() throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
        try {
         storeRow();
       } catch (Exception ex) {
           throw new EJBException("ejbStore: " + 
              ex.getMessage());
       }
    }
    
    public void setEntityContext(javax.ejb.EntityContext entityContext) throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
      this.context = entityContext;
      try {
         makeConnection();
      } catch (Exception ex) {
          throw new EJBException("Unable to connect to database. " +
             ex.getMessage());
      }
    }
    
    public void unsetEntityContext() throws javax.ejb.EJBException, java.rmi.RemoteException 
    {
        try {
         con.close();
      } catch (SQLException ex) {
          throw new EJBException("unsetEntityContext: " + ex.getMessage());
      }
    }
    
  
    //home method
    public String ejbCreate(String userName,String bookId) throws CreateException 
    {
       try {
          this.id=insertRow(userName, bookId);
       } catch (Exception ex) {
           throw new EJBException("ejbCreate: " + 
              ex.getMessage());
       }

       this.userName = userName;
       this.bookId = bookId;
//       this.borrowDate = ;
//       this.returned=new String("0");

       return id;
    }
    
    public void ejbPostCreate(String userName,String bookId) 
    {
    }
    
    public String ejbFindByPrimaryKey(String primaryKey) throws FinderException 
    {
      boolean result;
      try {
         result = selectByPrimaryKey(primaryKey);
       } catch (Exception ex) {
           throw new EJBException("ejbFindByPrimaryKey: " + 
              ex.getMessage());
       }
      if (result) {
         return primaryKey;
      }
      else {
         throw new ObjectNotFoundException
            ("Row for id " + primaryKey + " not found.");
      }
    }
    
    public Collection ejbFindByUserName(String userName) throws FinderException 
    {
      Collection result;

      try {
         result = selectByUserName(userName);
       } catch (Exception ex) {
           throw new EJBException("ejbFindByUserName " + 
              ex.getMessage());
       }
       return result;
    }
    
    public Collection ejbFindByUserNameBookId(String userName,String bookId) throws FinderException 
    {
      Collection result;

      try {
         result = selectByUserNameBookId(userName,bookId);
       } catch (Exception ex) {
           throw new EJBException("ejbFindByUserName " + 
              ex.getMessage());
       }
       return result;
    }
    
    
    
    //business method
    public String getUserName() throws RemoteException
    {
        return userName;
    }
   
   
   public String getBookId() throws RemoteException
   {
       return bookId;
   }
   
 
   public String getBorrowDate() throws RemoteException
   {
       return borrowDate;
   }
   
  
   public String getReturned() throws RemoteException
   {
       return returned;
   }
   
  
   public void setReturned() throws RemoteException
   {
        returned="1";
   }
     
    //========================helper functions========================
    private void makeConnection() throws NamingException, SQLException 
    {
      InitialContext ic = new InitialContext();
      DataSource ds = (DataSource) ic.lookup(dbName);
      con =  ds.getConnection();
    }
    
    private boolean selectByPrimaryKey(String primaryKey) throws SQLException 
    {

      String selectStatement =
            "select id " +
            "from borrow where id = ? ";
      PreparedStatement prepStmt =con.prepareStatement(selectStatement);
      prepStmt.setInt(1, Integer.parseInt(primaryKey));

      ResultSet rs = prepStmt.executeQuery();
      boolean result = rs.next();
      prepStmt.close();
      return result;
    }
    
    private Collection selectByUserName(String userName) throws SQLException 
    {

      String selectStatement =
            "select id " +
            "from borrow where user_name = ? and returned='0'";
      PreparedStatement prepStmt = 
            con.prepareStatement(selectStatement);

      prepStmt.setString(1, userName);
      ResultSet rs = prepStmt.executeQuery();
      ArrayList a = new ArrayList();

      while (rs.next()) {
         String id = rs.getString(1);
         a.add(id);
      }

      prepStmt.close();
      return a;
    }
    
    private Collection selectByUserNameBookId(String userName,String bookId) throws SQLException 
    {

      String selectStatement =
            "select id " +
            "from borrow where user_name = ? and book_id like ? and returned='0'";
      PreparedStatement prepStmt = 
            con.prepareStatement(selectStatement);

      prepStmt.setString(1, userName);
      prepStmt.setString(2, "%"+bookId+"%");
      ResultSet rs = prepStmt.executeQuery();
      ArrayList a = new ArrayList();

      while (rs.next()) {
         String id = rs.getString(1);
         a.add(id);
      }

      prepStmt.close();
      return a;
    }
    
    private void loadRow() throws SQLException {

      String selectStatement =
            "select user_name,book_id,borrow_date,returned " +
            "from borrow where id = ? ";
      PreparedStatement prepStmt = 
            con.prepareStatement(selectStatement);

      prepStmt.setInt(1, Integer.parseInt(this.id));

      ResultSet rs = prepStmt.executeQuery();

      if (rs.next()) {
         this.userName = rs.getString(1);
         this.bookId = rs.getString(2);
         this.borrowDate = rs.getString(3);
         this.returned = rs.getString(4);
               
         prepStmt.close();
      }
      else {
         prepStmt.close();
         throw new NoSuchEntityException("Row for id " + id +
            " not found in database.");
      }
   }


   private void storeRow() throws SQLException 
   {
      String updateStatement =
            "update borrow set user_name =  ? ," +
            "book_id = ? , borrow_date = ? , returned = ? " +
            "where id = ?";
      PreparedStatement prepStmt = 
            con.prepareStatement(updateStatement);

      prepStmt.setString(1, userName);
      prepStmt.setString(2, bookId);
      prepStmt.setString(3, borrowDate);
      prepStmt.setString(4, returned);
      prepStmt.setInt(5, Integer.parseInt(this.id));
      int rowCount = prepStmt.executeUpdate();
      prepStmt.close();

      if (rowCount == 0) {
         throw new EJBException("Storing row for id " + id + " failed.");
      }
   }
   
   private String insertRow (String userName, String bookId) throws SQLException 
   {
          System.out.println("In InsertRow,userName="+userName+",book_id="+bookId);
          String insertStatement =
                "insert into borrow(user_name,book_id,borrow_date,returned) values(?,?,?,?) ";
          PreparedStatement prepStmt = 
                con.prepareStatement(insertStatement);

          String curTime=(java.util.Calendar.getInstance().getTime()).toString();
          
          prepStmt.setString(1, userName);
          prepStmt.setString(2, bookId);
          prepStmt.setString(3, curTime);
          prepStmt.setString(4, "0");
          //==================need lock====================
          
          //System.out.println("Insert sql:"+insertStatement);
          prepStmt.executeUpdate();
          prepStmt.close();
          
          System.out.println("Insert complete! date="+(java.util.Calendar.getInstance().getTime()).toString());
          //get the id
          String selectStatement =
            "select id " +
            "from borrow where user_name=?  order by id desc ";
          prepStmt = con.prepareStatement(selectStatement);
          
          prepStmt.setString(1,userName);

          ResultSet rs = prepStmt.executeQuery();
          
          rs.next();
          String result=rs.getString(1);
          
          prepStmt.close();
          //=================unlock====================
          System.out.println("End InsertRow");
          
          this.id=result;
          this.userName=userName;
          this.bookId=bookId;
          this.borrowDate=curTime;
          this.returned="0";
          
          return result;
   }
    
    
}