tender.java

一个简单的持久化类

package servlet;
import java.io.*;
import java.sql.*;
import java.util.Calendar;


import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Tender extends HttpServlet {
	
	String DBDriver = null; 
	String DBLocation = null; 
	String DBUser = null; 
	String DBPwd = null;
	Connection conn = null;
	Statement stmt = null; 
	ResultSet rs = null;
	int flag = 1;
	
	public Tender() {
		super();
	}

	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request,response);
	}

	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		DBDriver = getServletContext().getInitParameter("DBDriver");
		DBLocation = getServletContext().getInitParameter("DBLocation");
		DBUser = getServletContext().getInitParameter("DBUser");
		DBPwd = getServletContext().getInitParameter("DBPwd");
	}
	
	public void getConn() throws SQLException, ClassNotFoundException{
		Class.forName(DBDriver);
		conn = DriverManager.getConnection(DBLocation, DBUser, DBPwd); 
		
		stmt = conn.createStatement(
				ResultSet.TYPE_SCROLL_SENSITIVE,
				ResultSet.CONCUR_UPDATABLE);
	}
	
	public void closeConn(){
		try {
			if(rs!=null)
				rs.close();
			if(stmt!=null)
				stmt.close();
			if(conn!=null)
				conn.close();
			
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException { 
    	showQuery(request,response);
    	
    }
    
    public void showQuery (HttpServletRequest request, HttpServletResponse response) 
    throws ServletException,IOException{
    	String tenderno = request.getParameter("tenderno");
    	String sql = "select * from tender where tenderno='" + tenderno + "'";
    	try {
    		getConn();
			rs = stmt.executeQuery(sql);
			rs.last();
    		int num = rs.getRow();
    		Pojo[] pj = new Pojo[num];
    		rs.beforeFirst();
    		for(int i=0;i<num;i++){
    			rs.next();
    			pj[i] = new Pojo(rs);    			
    		}
			request.setAttribute("pj", pj);
			flag=1;
		} catch (SQLException e) {
			flag=0;
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			flag=0;
			e.printStackTrace();
		} finally {
			closeConn();
			if(flag==1){
				request.getRequestDispatcher("/jsp/showTender.jsp").forward(request,response);
			}else if(flag==0){
				request.setAttribute("errorMessage", "数据库出错，请与管理员联系。");
				request.getRequestDispatcher("/jsp/error.jsp").forward(request,response);
			}
		}
    }
   
}