我的RoomBean.java可以run但是RoomDataBean.java不可以compile

小今 · 发表于 4-11-2005 10:55 AM

我的RoomBean.java可以run但是RoomDataBean.java不可以compile

以下是我的RoomBean.java和RoomDataBean.java，我的RoomBean.java可以run但是RoomDataBean.java不可以compile.问题出在那里呢？

这是RoomBean.java 的code

package dbentity;

public class RoomBean
{
   private String
roomID,roomType,checkIn,checkOut,numberOfDay,specialFacilities;

public void setRoomID(String id)
{
   roomID = id;
}

public String getRoomID()
{
      return roomID;
}

public void setRoomType(String type)
{
   roomType = type;
}

   public String getRoomType()
{
      return roomType;
}

public void setCheckIn(String day)
{
   checkIn = day;
}

public String getCheckIn()
{
      return checkIn;
}

public void setCheckOut(String day)
{
   checkOut = day;
}

public String getCheckOut()
{
      return checkOut;
}

   public void setNumberOfDay(String number)
{
   numberOfDay = number;
}

public String getNumberOfDay()
{
      return numberOfDay;
}

   public void setSpecialFacilities(String facilities)
{
   specialFacilities = facilities;
}

public String getSpecialFacilities()
{
      return specialFacilities;
}
}

这是RoomDataBean.java(有问题）

package dbentity;

import java.io.*;
import java.sql.*;
import java.util.*;

public class RoomDataBean
{
   private Connection connection;
   private PreparedStatement addRecord, getRecords;
   private Statement statement;

public RoomDataBean() throws Exception
{
   System.setProperty("jdbc.odbc.system.home","c:/Microsoft Access");
   Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

   connection = DriverManager.getConnection("jdbc:odbc:Room    Accommodation.mdb");

   statement = connection.createStatement();
  }

public ArrayList getRoomList() throws SQLException
{

   ArrayList roomList = new ArrayList();

   ResultSet results =statement.executeQuery(
      "SELECT roomID,roomType,checkIn,checkOut,numberOfDay,specialFacilities FROM room");

   while (results.next() )
   {
      RoomBean room = new RoomBean();

   room.setRoomID( results.getString(1) );
   room.setRoomType( results.getString(2) );
   room.setCheckIn( results.getString(3) );
   room.setCheckOut( results.getString(4) );
   room.setNumberOfDay( results.getString(5) );
   room.setSpecialFacilities( results.getString(6) );

   roomList.add(room);
   }
      return roomList;
   }

      public void addRoom(RoomBean room ) throws SQLException
      {
         statement.executeUpdate( " INSERT INTO room (roomID,roomType,checkIn,checkOut,numberOfDay,specialFacilities) VALUES ( ' " +room.getRoomID() +" ',' "+room.getRoomType()+" ',' "+room.getCheckIn()+ " ',' "+room.getCheckOut()+ " ',' "+room.getNumberOfDay()+" ',' "+room.getSpecialFacilities()+" ')");

      }

      protected void finalize()
      {

         try{
            statement.close();
            connection.close();
         }

      catch(SQLException sqlException){
         sqlException.printStackTrace();
         }

   }


}

请各位大大帮帮忙，感激不尽。。。

jasonmun · 发表于 4-11-2005 11:01 AM

连error msg 都没有吗?

小今 · 发表于 4-11-2005 11:55 AM

有啊，就是compile不到。有几个

RoomBean room = new RoomBean();

public void addRoom(RoomBean room ) throws SQLException

jasonmun · 发表于 4-11-2005 12:10 PM

while Loop create 同样名字的obj..
我想这是问题所在吧..

while (results.next() )
   {
      RoomBean room = new RoomBean();
      ...
   roomList.add(room);
   }
      return roomList;
   }

小今 · 发表于 4-11-2005 12:38 PM

这样的话 public void addRoom(RoomBean room ) throws SQLException 有问题吗？

显示全部楼层 · 发表于 4-11-2005 11:32 PM

1。RoomBean 就取名为 Room。以 J2EE 的标准，人人都知道它是一个 Javabean。

2。这个 Javabean 是一个 value object，记得要 implement serializable。(this is one of the J2EE best practices)。如果没有 implement serializable，在 single server 里操作当然不会有问题。但是未来这个 application 要 deploy 到 cluster environment 时候，它就不能正常操作了。在 value object 里 implement serializable 也只是花你几秒的时间吧。。。

3。Data Access 方面用 DAO (Data Access Object) Pattern。以下的 code 是比较简单的 DAO 方式：

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Enumeration;
import java.util.Properties;
import java.util.ResourceBundle;
/**
* This class gets a JDBC connection for DAOs to perform required JDBC
* operations and also closes the resources when JDBC operations are finished.
*
* @author Seagull Ng
*/
public class J2EEServices
{
private static Connection conn = null;
/**
* This method tries to create a JDBC connection by loading up the
* parameters from Connection.properties file.
*
* @return Returns a connection.
*/
public static Connection getConnection()
{
// Load the properties file to get the connection information.
try
{
Properties connProp = loadParams("Connection");
String driver = (String) connProp.get("DriverName");
Class.forName(driver);
conn = java.sql.DriverManager.getConnection((String) connProp
.get("URL")
+ ":"
+ (String) connProp.get("Port")
+ "/"
+ (String) connProp.get("DB"), (String) connProp
.get("UserName"), (String) connProp.get("Password"));
}
catch (Exception e)
{
System.err.println("Fail to get JDBC connection:");
System.err.println(e.getMessage());
}
return conn;
}
/**
* This method closes the JDBC resources to prevent resources leak.
*
* @param rs -
* ResultSet
* @param stmt -
* Statement
* @param conn -
* Connection
*/
public static void closeDBResources(ResultSet rs, Statement stmt,
Connection conn)
{
try
{
if (rs != null)
rs.close();
}
catch (SQLException e)
{
System.err.println("Error closing resultset: " + e);
}
try
{
if (stmt != null)
stmt.close();
}
catch (SQLException e)
{
System.err.println("Error closing statement: " + e);
}
try
{
if (conn != null)
conn.close();
}
catch (SQLException e)
{
System.err.println("Error closing connection: " + e);
}
}
/**
* This method reads a properties file which is passed as the parameter to
* it and load it into a java Properties object and returns it.
*
* @param file - Name of the file that has to be loaded.
* @return prop - Properties of database connection parameters.
* @throws java.io.IOException - In case of unexpected exceptions.
*/
private static Properties loadParams(String file) throws java.io.IOException
{
// Loads a ResourceBundle and creates Properties from it
Properties prop = new Properties();
ResourceBundle bundle = ResourceBundle.getBundle(file);
Enumeration e = bundle.getKeys();
String key = null;
while (e.hasMoreElements())
{
key = (String) e.nextElement();
prop.put(key, bundle.getObject(key));
}
return prop;
}
}

复制代码

Connection.properties file

DriverName=com.mysql.jdbc.Driver
URL=jdbc:mysql://yourdomain.com
Port=3306
DB=ej605c14
UserName=ej605c14
Password=bob_the_builder

复制代码

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
/**
* This class provides Course related JDBC operations.
*
* @author Seagull Ng
*/
public class CourseDAO
{
/**
* strSqlGetCourse - Query string to get a course information by courseId.
*/
private static final String strSqlGetCourse = "SELECT * FROM A2Courses WHERE courseId = ?";
/**
* strSqlGetCourses - Query string to get all courses.
*/
private static final String strSqlGetCourses = "SELECT * FROM A2Courses";
/**
* strSqlInsertCourse - Query string to insert a course.
*/
private static final String strSqlInsertCourse = "INSERT INTO A2Courses VALUES (?, ?, ?, ?, ?)";
/**
* This method gets a course by matching a course id.
*
* @param courseId Course ID
* @return Course object populated with course information
* @exception SQLException
*/
public static Course getCourse(String courseId)
{
Course course = new Course();
PreparedStatement stmt = null;
ResultSet rs = null;
try
{
Connection conn = J2EEServices.getConnection();
stmt = conn.prepareStatement(strSqlGetCourse);
stmt.setString(1, courseId);
stmt.execute();
rs = stmt.getResultSet();
while (rs.next())
{
course.setCourseId(rs.getString("courseId"));
course.setCourseName(rs.getString("courseName"));
course.setCourseDesc(rs.getString("courseDesc"));
course.setCoursePeriod(rs.getString("coursePeriod"));
course.setCoursePrice(rs.getDouble("coursePrice"));
}
J2EEServices.closeDBResources(rs, stmt, conn);
}
catch (SQLException e)
{
System.err.println("SQL Exception in CourseDAO.getCourse(): " + e);
}
return course;
}
/**
* This method gets all courses.
*
* @return a collection of Course objects in a Map
* @exception SQLException
*/
public static List getCourses()
{
List courses = new ArrayList();
Statement stmt = null;
ResultSet rs = null;
try
{
Connection conn = J2EEServices.getConnection();
stmt = conn.createStatement();
stmt.execute(strSqlGetCourses);
rs = stmt.getResultSet();
while (rs.next())
{
Course course = new Course();
course.setCourseId(rs.getString("courseId"));
course.setCourseName(rs.getString("courseName"));
course.setCourseDesc(rs.getString("courseDesc"));
course.setCoursePeriod(rs.getString("coursePeriod"));
course.setCoursePrice(rs.getDouble("coursePrice"));
courses.add(course);
}
J2EEServices.closeDBResources(rs, stmt, conn);
}
catch (SQLException e)
{
System.err.println("SQL Exception in CourseDAO.getCourses(): " + e);
}
return courses;
}
/**
* This method inserts a course record into the table.
*
* @param courseId Course ID
* @param courseName Course Name
* @param courseDesc Course Description
* @param coursePeriod Course Period (eg. Fall 2005)
* @param coursePrice Course Price
* @return either the row count for INSERT, or 0 for SQL statements that return nothing
* @exception SQLException
*/
public static int insertCourse(String courseId, String courseName, String courseDesc, String coursePeriod, double coursePrice)
{
int res = 0;
PreparedStatement stmt = null;
ResultSet rs = null;
try
{
Connection conn = J2EEServices.getConnection();
stmt = conn.prepareStatement(strSqlInsertCourse);
stmt.setString(1, courseId);
stmt.setString(2, courseName);
stmt.setString(3, courseDesc);
stmt.setString(4, coursePeriod);
stmt.setDouble(5, coursePrice);
res = stmt.executeUpdate();
J2EEServices.closeDBResources(rs, stmt, conn);
}
catch (SQLException e)
{
System.err.println("SQL Exception in CourseDAO.insertCourse(): " + e);
}
return res;
}
}

复制代码

显示全部楼层 · 发表于 4-11-2005 11:49 PM

原帖由 jasonmun 于 4-11-2005 12:10 PM 发表
while Loop create 同样名字的obj..
我想这是问题所在吧..

while (results.next() )
   {
      RoomBean room = new RoomBean();
      ...
   roomList.add(room);
   }
      retu ...

每 loop 一次就产生一个新的 room，然后把已经存值的 room 放到一个 collection 里。这样会有什么问题？

小今 · 发表于 5-11-2005 07:55 PM

while (results.next() )
   {
      RoomBean room = new RoomBean();
      ...
   roomList.add(room);
   }
      return roomList;
   }

我也是跟着以上的code来写呀但RoomBean room = new RoomBean() 就是有error。RoomDataBean.java:50:cannot resolve symbol。Symbol : class RoomBean.

小今 · 发表于 5-11-2005 08:12 PM

是package 的问题吗？一定要用package 吗？如果是应该如何写呢？

这个是connection 不是package,是吗？

package dbentity;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBConnection{

String strUrl = "";
Connection conn = null;

public DBConnection()
{

}

public Connection getMicrosoftAccessConnection()
{
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"

;
this.strUrl = "jdbc

dbc:Microsoft Access:Room                                                       Accommodation.mdb";
      this.conn = DriverManager.getConnection( strUrl,"root", "" );

      System.out.println("URL: " + strUrl);
      System.out.println("Connection: " + conn);
}
catch( ClassNotFoundException cnfe )
      {
        cnfe.printStackTrace();
      }
catch( SQLException sqle )
      {
sqle.printStackTrace();
      }

return conn;

}

}

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我的RoomBean.java可以run但是RoomDataBean.java不可以compile

Javabean & Data Access Layer

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