2021-10-29

最新推荐文章于 2025-05-07 19:46:16 发布

霍都j

最新推荐文章于 2025-05-07 19:46:16 发布

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分类专栏： java 文章标签： java

本文链接：https://blog.youkuaiyun.com/ITyikaka/article/details/121527047

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该博客内容涉及Java Servlet在处理数据库操作时遇到的问题。在尝试插入数据后，作者尝试使用ResultSet的previous()方法上移游标进行重复检查，但遇到了不支持此操作的错误。博客详细记录了代码实现过程，包括获取请求参数、建立数据库连接、执行SQL以及异常处理。作者最终通过调整代码解决了问题。

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resultset中previous方法无法使用

只进结果集不支持请求的操作

package zy.hg.servlet;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import zy.hg.javabean.jdbcConn;

/**
 * Servlet implementation class classAddServlet
 */
@WebServlet("/classAddServlet")
public class classAddServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public classAddServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
		
		System.out.println("classAddservlet执行成功");
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		
		response.setHeader("content-type","text/html; charset=UTF-8");
		
		response.setCharacterEncoding("UTF-8");//请求和响应都设置成ufg-8
		request.setCharacterEncoding("utf-8");
		
		String bjbh=request.getParameter("bjbh");
		String bjmc=request.getParameter("bjmc");
		System.out.println(bjbh);
		System.out.println(bjmc);
		
		Connection con=null;
		PreparedStatement state=null;
		ResultSet rs=null;
		String sql="insert into class2 VALUES('"+bjmc+"','"+bjbh+"')";
		con=jdbcConn.getConnection();
		
		try {
			state=con.prepareStatement(sql);
			state.executeUpdate();
			//rs=state.executeQuery();
//			if (rs.next()) {
//				String bjmc=rs.getString("banji");
//				System.out.println(bjmc);
//				response.getWriter().write(bjmc);
//			}else {
//				System.out.println();
//			}
		} catch (SQLException e) {
			
			e.printStackTrace();
		}finally {
			jdbcConn.free(rs, state, con); 
		}
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//doGet(request, response);
		
		System.out.println("classAddservlet执行成功");
		response.setHeader("content-type","text/html; charset=UTF-8");
		response.setCharacterEncoding("UTF-8");//请求和响应都设置成ufg-8
		request.setCharacterEncoding("utf-8");
		
		String bjbh=request.getParameter("bjbh");
		
		System.out.println(bjbh);

		
		Connection con=null;
		PreparedStatement state=null;
		ResultSet rs=null;
		String sql="select bjno from class2";
		con=jdbcConn.getConnection();
		
		try {
			state=con.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
			//state.executeUpdate();
			rs=state.executeQuery();
			while (rs.next()) {
				String bjno02=new String(rs.getString("bjno"));
				String bjno=bjno02.trim(); 
				//System.out.println(bjno);
				if (bjbh.equals(bjno)) {
					response.getWriter().write("编号已经存在！");
					break;
				}
				if((rs.next())==false) {
					System.out.println("next!!!");
					response.getWriter().write("编号尚未存在！");
					
					break;
				}
				rs.previous();//这里我将游标上移一次，但是因为这个结果集只能迭代一次，
				//所以resultset下的某些方法就不能使用，加上以下便可使用
			}
			
			
		} catch (SQLException e) {
			
			e.printStackTrace();
		}finally {
			jdbcConn.free(rs, state, con); 
		}
		
	}

}