resultsetcontroller.java

jsp+javabean写的论坛

package com.alumni.bean;
import java.sql.*;

public class ResultSetController
{
	private Connection conn;
	private ResultSet rs;
	private Statement stmt;
	
	private String accessURL;
	private String queryString;
	
	private int currentPageNum;//当前页
	private int rowsPerPage;//每页显示的数据行数
	private int totalPages;//总页数
	private int totalCounts;//总记录数
	private boolean isEmpty;//是否有数据
	private int count;//每页记录的记数器
	
	//初始化参数（构造器）
	public ResultSetController()
	{
		this.conn=null;
		this.rs=null;
		this.stmt=null;
		
		this.accessURL="";
		this.queryString="";
		
		this.currentPageNum=1;
		this.rowsPerPage=10;
		this.totalPages=0;
		this.totalCounts=0;
		this.isEmpty=true;
		this.count=0;
	}
	
	
	//运行主方法
	public void run() throws SQLException
	{
		//连接到ACCESS数据库
		if(this.conn==null)
		{
			this.connectToAccess(this.accessURL);
		}
		
		//初始化数据
		this.initData();
		
		//设定指针的位置
		this.moveToCurrentPage(currentPageNum);
		
	}
	
	
	//初始化数据
	private void initData() throws SQLException
	{
		this.stmt=this.conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
		this.rs=this.stmt.executeQuery(this.queryString);
		//计算总记录数
		while(this.rs.next())
		{
			this.totalCounts++;
		}
		this.rs.beforeFirst();
		//判断数据是否为空
		if(this.totalCounts==0)
		{
			this.isEmpty=true;
			this.totalCounts=0;
			//默认时总页数为1页
			this.totalPages=1;
		}
		else
		{
			this.isEmpty=false;
			//计算总页数
			if((this.totalCounts%this.rowsPerPage)==0)
			{
				this.totalPages=this.totalCounts/this.rowsPerPage;
			}
			else
			{
				this.totalPages=(this.totalCounts/this.rowsPerPage)+1;
			}
		}
	}
	
	
	//连接到ACCESS数据库
	private void connectToAccess(String accessURL)
	{
		try
		{
			DBConnection dbc=new DBConnection();
			this.conn=dbc.getConnectionToAccess(this.accessURL);
		}
		catch(SQLException sqle)
		{
			sqle.printStackTrace();
		}
		catch(ClassNotFoundException cnfe)
		{
			cnfe.printStackTrace();
		}
	}
	
	
	//判断是否有数据
	public boolean isEmpty()
	{
		return this.isEmpty;
	}
	
	
	//根据设定的每页显示的记录数判断是否能继续输出数据
	public boolean isAvailable() throws SQLException
	{
		if(this.rs.next()&&this.count++<this.rowsPerPage)
		{
			return true;
		}
		else
		{
			count=0;//计数器归零
			return false;
		}
	}
	
	
	//是否是数据顶部
	public boolean isBeforeFirst() throws SQLException
	{
		return this.rs.isBeforeFirst();
	}
	
	
	//是否是数据底部
	public boolean isAfterLast() throws SQLException
	{
		return this.rs.isAfterLast();
	}


	//是否是第一条数据
	public boolean isFirst() throws SQLException
	{
		return this.rs.isFirst();
	}
	
	
	//是否是最后一条数据
	public boolean isLast() throws SQLException
	{
		return this.rs.isLast();
	}
	
	//抓住数据库连接对象
	public void setConnectionObject(Connection conn)
	{
		this.conn=conn;
	}
	
	//获得数据库连接对象
	public Connection getConnectionObject()
	{
		return this.conn;
	}
	
	//设定数据库名
	public void setAccessURL(String accessURL)
	{
		this.accessURL=accessURL;
	}
	
	
	//设定查询语句
	public void setQueryString(String qs)
	{
		this.queryString=qs;
	}
	
	
	//设定当前显示的页面
	public void setCurrentPageNum(int num)
	{
		this.currentPageNum=num;
	}
	
	
	//获得当前显示的页码
	public int getCurrentPageNum()
	{
		return this.currentPageNum;
	}
	
	
	//设定每页可显示的数据行数
	public void setRowsPerPage(int rows)
	{
		this.rowsPerPage=rows;
	}
	
	
	//（按指定的索引）取得当前指针位置的数据
	public String getData(int column) throws SQLException
	{
		return this.rs.getString(column)!=null?this.rs.getString(column):"N/A";
	}
	
	
	//（按指定的列名）取得当前指针位置的数据
	public String getData(String columnName) throws SQLException
	{
		return this.rs.getString(columnName)!=null?this.rs.getString(columnName):"N/A";
	}
	
	
	//获得当前每页可显示的数据行数
	public int getRowsPerPage()
	{
		return this.rowsPerPage;
	}
	
	
	//获得总页数
	public int getTotalPages()
	{
		return this.totalPages;
	}
	
	
	//获得总记录数
	public int getTotalCounts()
	{
		return this.totalCounts;
	}
	
	
	//移动指针到指定的页面
	public void moveToCurrentPage(int pageNum) throws SQLException
	{
		for(int i=1;i<this.currentPageNum;i++)
		{
			for(int j=0;j<this.rowsPerPage;j++)
			{
				this.moveToNext();
			}
		}
	}
	
	
	//把指针移动到下一条记录
	public boolean moveToNext() throws SQLException
	{
		return this.rs.next();
	}
	
	
	//把指针移动到前一条记录
	public boolean moveToPrevious() throws SQLException
	{
		return this.rs.previous();
	}
	
	
	//把指针移动到第一条记录
	public boolean moveToFirst() throws SQLException
	{
		return this.rs.first();
	}
	
	
	//把指针移动到最后一条记录
	public boolean moveToLast() throws SQLException
	{
		return this.rs.last();
	}
	
	
	//恢复指针到原始位置
	public void moveToTop() throws SQLException
	{
		this.rs.beforeFirst();
	}
	
	
	//把指针移动到最底部
	public void moveToBottom() throws SQLException
	{
		this.rs.afterLast();
	}
	

	//结束运行
	public void disconnect() throws Throwable
	{
		if(this.conn!=null)
		{
			this.conn.close();
		}
	}
	
	
	//当WEB服务器停止服务时回收资源
	protected void finalize() throws Throwable
	{
		this.disconnect();
		if(this.rs!=null)
			this.rs.close();
		if(this.stmt!=null)
			this.stmt.close();
	}
}