基于图书管理系统的查

entity层和DBUtil层同增的操作，今天是修改操作（代码部分加上之前的）

dao层：

package dao;

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;

import DBUtil.DBUtil;
import entity.Book;

public class Dao {
    //根据书的姓名查找
    public Book getbyname(String bname) {
        String sql = "select * from Book where bname ='" + bname + "'";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;
        Book b = null;
        
        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            while (rs.next()) {
                int id = rs.getInt("id");
                String bianhao = rs.getString("bianhao");
                String bname2 = rs.getString("bname");
                String wname = rs.getString("wname");
                String bhome=rs.getString("bhome");
                int num = rs.getInt("num");
                b = new Book(id,bianhao,bname2,wname,bhome,num);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return b;
    }

    //添加新书信息
    public boolean addBook(Book stu) {
        Connection conn = DBUtil.getConn();
        PreparedStatement pstmt = null;
        boolean f = false;
        int a = 0;
        try {
            String sql = "insert into Book(bianhao,bname,wname,bhome,num) value(?,?,?,?,?)";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, stu.getBianhao());
            pstmt.setString(2, stu.getBname());
            pstmt.setString(3, stu.getWname());
            pstmt.setString(4, stu.getBhome());
            pstmt.setLong(5, stu.getNum());
            a = pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(pstmt, conn);
        }
        if (a > 0)
            f = true;

        return f;
    }
    //删除图书信息，根据书名删除
     public boolean deleteBook(String bname)
     {
         String sql="delete from Book where bname='" + bname + "'";
         Connection conn = DBUtil.getConn();
         Statement state = null;
         int a = 0;
         boolean f = false;
         try {
             state = conn.createStatement();
             a = state.executeUpdate(sql);
         } catch (SQLException e) {
             e.printStackTrace();
         } finally {
             DBUtil.close(state, conn);
         }
         
         if (a > 0) {
             f = true;
         }
         return f;
     }

    //更新图书信息，获取的是书的姓名
    public boolean updateBook(Book stu,String old_bname) {
        String sql = "update Book set bianhao='" + stu.getBianhao() + "', bname='" + stu.getBname() + "', wname='"
                + stu.getWname() + "',bhome='" + stu.getBhome() + "',num='" + stu.getNum() + "'where bname='"+old_bname+"'";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        boolean f = false;
        int a = 0;
        try {
            state = conn.createStatement();
            System.out.println("修改成功");
            a = state.executeUpdate(sql);
            System.out.println(a);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(state, conn);
        }

        if (a > 0) {
            f = true;
        }

        System.out.println(f);
        return f;
    }
    //浏览图书信息
    public List<Book> liulanbook() {
        String sql = "select * from Book";
        List<Book> list = new ArrayList<>();
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;

        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            Book bean = null;
            while (rs.next()) {
                int id = rs.getInt("id");
                String bianhao = rs.getString("bianhao");
                String bname = rs.getString("bname");
                String wname = rs.getString("wname");
                String bhome=rs.getString("bhome");
                int num = rs.getInt("num");
                bean = new Book(id,bianhao,bname,wname,bhome,num);
                list.add(bean);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }

        return list;
    }
    //模糊查询图书
    public List<Book> searchBook(String bname,String wname)
    {
        String sql = "select * from Book where ";
        if (bname != "") {
            sql += "bname like '%" +bname+ "%'";
        }
        if (wname != "") {
            sql += "wname like '%" +wname+ "%'";
        }
        
        List<Book> list = new ArrayList<>();
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;
        Book bean = null;
        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            while (rs.next()) {
                String bianhao = rs.getString("bianhao");
                String bname2 = rs.getString("bname");
                String wname2 = rs.getString("wname");
                String bhome=rs.getString("bhome");
                int num = rs.getInt("num");
                bean = new Book(bianhao,bname2,wname2,bhome,num);
               
                list.add(bean);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return list;
    }

}

servlet层：

package servlet;

import java.io.IOException;
import java.util.List;

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 dao.Dao;
import entity.Book;

@WebServlet("/Servlet")
public class Servlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    Dao dao = new Dao();

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String method = req.getParameter("method");
        if ("addBook".equals(method)) {
            addBook(req, resp);
        } else if ("liulanbook".equals(method)) {
            liulanbook(req, resp);
        } else if ("searchBook".equals(method)) {
            searchBook(req, resp);
        } else if ("getbyname".equals(method)) {
            getbyname(req, resp);
        } else if ("deleteBook".equals(method)) {
            deleteBook(req, resp);
        }else if("updateBook".equals(method)) {
            updateBook(req,resp);
        }
    }

    private void deleteBook(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        // TODO 自动生成的方法存根
        req.setCharacterEncoding("utf-8");
        String bname = req.getParameter("bname");
        if (dao.deleteBook(bname)) {
            req.setAttribute("message", "删除成功");
            req.getRequestDispatcher("Servlet?method=liulanbook2").forward(req, resp);
        } else {
            req.setAttribute("message", "删除失败");
            req.getRequestDispatcher("Servlet?method=liulanbook2").forward(req, resp);
        }
    }

    private void addBook(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String bianhao = req.getParameter("bianhao");
        String bname = req.getParameter("bname");
        String wname = req.getParameter("wname");
        String bhome = req.getParameter("bhome");
        int num = Integer.parseInt(req.getParameter("num"));
        Book book = new Book(bianhao, bname, wname, bhome, num);
        if (dao.addBook(book)) {
            req.setAttribute("book", book);
            req.setAttribute("message", "添加成功");
            req.getRequestDispatcher("addBook.jsp").forward(req, resp);
        } else {
            req.setAttribute("message", "书籍信息重复，请重新输入");
            req.getRequestDispatcher("addBook.jsp").forward(req, resp);
        }
    }

    private void searchBook(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        req.setCharacterEncoding("utf-8");
        String bname = req.getParameter("bname");
        String wname = req.getParameter("wname");

        List<Book> tens = dao.searchBook(bname, wname);
        if (tens == null) {
            req.setAttribute("message", "没有该书");
            req.getRequestDispatcher("searchbook.jsp").forward(req, resp);
        } else {
            req.setAttribute("tens", tens);
            req.getRequestDispatcher("list.jsp").forward(req, resp);
        }
    }

   private void getbyname(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
       req.setCharacterEncoding("utf-8");
       String bname = req.getParameter("bname");
       Book b=new Book();
       b.setBname(bname);
       b= dao.getbyname(bname);
       if(b==null)
       {
           req.setAttribute("message", "未找到该书籍");
           req.getRequestDispatcher("xiugaiBook.jsp").forward(req, resp);
       }
       else 
       {
           req.setAttribute("b", b);
           req.getRequestDispatcher("xiugai2.jsp").forward(req,resp);
       }
   }  
    private void liulanbook(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        req.setCharacterEncoding("utf-8");

        List<Book> tens = dao.liulanbook();
        req.setAttribute("tens", tens);
        req.getRequestDispatcher("list.jsp").forward(req, resp);
    }

     private void updateBook(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String old_bname = req.getParameter("old_bname");
            String bianhao=req.getParameter("bianhao");
            String bname = req.getParameter("bname");
            String wname= req.getParameter("wname");
            String bhome = req.getParameter("bhome");
            int num = Integer.parseInt(req.getParameter("num"));
            Book b = new Book(bianhao, bname, wname, bhome, num);
            if (dao.updateBook(b,old_bname)) {
                req.setAttribute("message", "修改成功");
                req.getRequestDispatcher("Servlet?method=liulanbook2").forward(req, resp);
            }else {
                req.setAttribute("message", "修改失败");
                req.getRequestDispatcher("Servlet?method=liulanbook2").forward(req, resp);
            }
        }
}

searchBook.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
<%
          Object message = request.getAttribute("message");
          if(message!=null && !"".equals(message)){
      
     %>
          <script type="text/javascript">
               alert("<%=request.getAttribute("message")%>");
          </script>
     <%} %>
<h>查找书籍</h>
    <div class="content">
        <div class="main">
        <a href="reader.jsp">返回主页面</a>
        <br><br>
        <form name="form" action="Servlet?method=searchBook" method="post" ">
            <a>书名</a>&nbsp;&nbsp;<input type="text" name="bname" />
            <br><br>
            <a>作者名</a>&nbsp;&nbsp;<input type="text" name="wname" />
            <br><br>
            
            <input type="submit" value="查找" /></td>
        </form>
        </div>
    </div>
</body>
</html>

我这里的查询功能放在了读者功能页，功能一样，点击查询图书信息，跳转到查询页：

 可以根据书名或作者名进行模糊查找，例如输入作者名海明威：

 查找成功：