delbookcontroller.java

学习jsp时做的一个书馆

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import library.DBConnection;


public class delBookController extends Controller {
	 public void doPost (HttpServletRequest req,
				HttpServletResponse res) throws ServletException, IOException {
		
		String id="";
        boolean del = true;
        boolean del2 = true; 
		HttpSession session = req.getSession();
		id = req.getParameter("id");
		String isbn ="";
		try{
			DBConnection connection = DBConnection.Instance();
			String sql = "select * from fakuan where findid  ='"+id+"'";
			ResultSet w = null;
			w = connection.runQuery(sql);
			if(w.next()){
				del =false;
			}
			sql = "select * from bookhavebr where findid ='"+id+"'";
			w = connection.runQuery(sql);
			if(w.next()){
				del2 =false;
			}
			sql = "select * from booktitle where findid ='"+id+"'";
			w = connection.runQuery(sql);
			while(w.next()){
				isbn = w.getString("isbn");
			}
		}catch(Exception e){
			sendErrorRedirect(req, res, e);
		}
		try{
			if(del2==false){
				res.sendRedirect("../admin/searchbookresult.jsp?jieguo3=failed1&id1="+id);		
			}else{
			    DBConnection connection = DBConnection.Instance();
			    boolean w = false;
			    String sql1 =  "delete from booktitle where findid ='"+id+"'";
			    w = connection.runUpdate(sql1);
			    String url ="jdbc:mysql://localhost/library?user=root&password=linux&useUnicode=true&characterEncoding=GB2312" ;
			    Connection conn= DriverManager.getConnection(url); 
			    Statement stmt=conn.createStatement();
			    sql1 = "update books set isinno = isinno-1 where isbn = '"+isbn+"'";
			    boolean rs=stmt.execute(sql1);
		        res.sendRedirect("../admin/searchBook.jsp?jieguo2=success&id="+id);		
			}
		}catch(Exception e){
			sendErrorRedirect(req, res, e);
		}
	 }
}