jsp一些注意事项

来源：互联网发布：拼多多是什么软件编辑：程序博客网时间：2024/05/17 17:43

private String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
private String url = "jdbc:odbc:fms";

整个Dao类

/* * To change this template, choose Tools | Templates * and open the template in the editor. */package db;/** * * @author Administrator */import java.sql.*;public class dao { private Connection con; private String driver = "sun.jdbc.odbc.JdbcOdbcDriver"; private String url = "jdbc:odbc:fms"; public dao(){ } public Connection getConnection() throws ClassNotFoundException,SQLException {  Class.forName(driver);  con = DriverManager.getConnection(url);  return con; } public int insert(String sql,Object ... args) throws SQLException,ClassNotFoundException{  PreparedStatement pstmt = getConnection().prepareStatement(sql);  int affectedRow = 0;  for(int i=0;i<args.length;i++){   //System.out.println((String)args[i]);       pstmt.setString(i+1, (String)args[i]);         }  affectedRow = pstmt.executeUpdate();   pstmt.close();   return affectedRow;   } public ResultSet query(String sql,Object ... args) throws SQLException,ClassNotFoundException {  PreparedStatement pstmt = getConnection().prepareStatement(sql);  ResultSet rs;  for(int i=0;i<args.length;i++){            pstmt.setString(i+1, (String)args[i]);  }  rs=pstmt.executeQuery();  //pstmt.close();  return rs; } public int delete(String sql,Object ... args) throws SQLException,ClassNotFoundException{  PreparedStatement pstmt = getConnection().prepareStatement(sql);  int affectedRow;  for(int i=0;i<args.length;i++){            pstmt.setString(i+1, (String)args[i]);  }  affectedRow =  pstmt.executeUpdate();  return affectedRow; }  public int update(String sql,Object ... args) throws SQLException,ClassNotFoundException{  PreparedStatement pstmt = getConnection().prepareStatement(sql);  int affectedRow;  for(int i=0;i<args.length;i++){       pstmt.setString(i+1, (String)args[i]);  }  affectedRow =  pstmt.executeUpdate();  return affectedRow; } public void closeConnection() throws Exception{  if(con != null && !con.isClosed()){   con.close();  } }  public static void main(String ... args){      dao dao1 = new dao();      try{        ResultSet rs = dao1.query("select * from client");        while(rs.next())        {            System.out.println("haha");        }      }      catch(Exception ex)      {          ex.printStackTrace();      }  }}

2.改变encoding

 public void doFilter(ServletRequest request, ServletResponse response,                         FilterChain chain)throws IOException, ServletException {if (debug) log("EncodingFilter:doFilter()");doBeforeProcessing(request, response);Throwable problem = null;try {            request.setCharacterEncoding("utf-8");        response.setCharacterEncoding("utf-8");    chain.doFilter(request, response);}

3.main的验证登陆机制

if(session.getAttribute("account")==null) //判断是否为空，为空则表示没有登录
{
response.sendRedirect("login.jsp?error=2");
}

4.loginvalidate的jsp页，不用servlet方法，注意<setproperty>用法

<jsp:setProperty name="admin" property="*">

可以自动获取有同名的request的parameter，放进去哪个name的实例中

<%@page contentType="text/html" pageEncoding="UTF-8"%><%@page import="java.sql.*" %><%@page import="java.util.*" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html>    <head>        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">        <title>JSP Page</title>        <jsp:useBean id="adminDao" class="db.AdminDao" scope="page" />        <jsp:useBean id="admin" class="db.Admin" scope="page" />        <jsp:setProperty name="admin" property="*" />    </head>    <body>        <%            admin = adminDao.login(admin.getAccount(), admin.getPassword());            if(admin!= null){                session.setAttribute("account", admin.getAccount());                response.sendRedirect("main.jsp");            }            else{                    response.sendRedirect("login.jsp?error=1");                }        %>    </body></html>

retrieveUserByName方法

注意那个break的用法

还有absolute之后游标就必须先读一次！

public List<Client> retrieveUserByName(String name,int neededPage) throws Exception//根据姓名查询   {      dao db = new dao();      List<Client> clients = new ArrayList<Client>();      try      {         ;         ResultSet rs = db.query(sql1,"%" + name + "%" );         if(rs.next()){ //如果rs有数据则计算页数等             rs.last();             totalRow = rs.getRow();             this.computeTotalPage(totalRow);         }        else         {            return clients; //无数据则直接返回空指针        }         if(neededPage>totalPage){             neededPage = totalPage;         }         int rowStart = pageSize*(neededPage-1)+1;         rs.absolute(rowStart);                  for(int i=0;i<pageSize;i++)         {                         clients.add(new Client(rs.getString(1), rs.getString(2), rs.getString(3), rs.getString(4), rs.getString(5), rs.getString(6)));            if(!rs.next())                break;         }      }      catch (SQLException ex)      {         throw new Exception(ex.getMessage());      }      finally      {         db.closeConnection();      }      return clients;   }

对应的servlet

注意session必须第一次的时候加回去content

request必须重新设每次的attribute

jsp给了servlet后，servlet用forward，原来的request已经消失！

要获得session，要用 httpsession 是javax。servlet。http里面的

protected void processRequest(HttpServletRequest request, HttpServletResponse response)    throws ServletException, IOException {        response.setContentType("text/html;charset=UTF-8");        request.setCharacterEncoding("UTF-8");        PrintWriter out = response.getWriter();                HttpSession session =request.getSession();  //获取用户的Session对象        ClientDao clientDao = new ClientDao();        List<Client> clients = new ArrayList<Client>();        RequestDispatcher rd ;        String content;     //获取搜索内容        String choice;      //获取用户的选择                int neededPage;    //用户要访问哪一页        try {            if(session.getAttribute("content")== null){  //是main传来的还是result页传来的？                content = request.getParameter("content");            }            else{                content = (String)session.getAttribute("content");            }            if(session.getAttribute("choice") == null){                choice = request.getParameter("choice");            }            else{                choice = (String)session.getAttribute("choice");            }            if(request.getParameter("neededPage")==null){       //初始时候没有需求页，就取第一页                neededPage = 1;            }            else{                neededPage = Integer.parseInt(request.getParameter("neededPage"));            }            if(choice.equals("name"))            {                clients = clientDao.retrieveUserByName(content,neededPage);            }            else if(choice.equals("unit"))            {                clients = clientDao.retrieveUserByUnit(content,neededPage);            }             else if(choice.equals("address"))            {                clients = clientDao.retrieveUserByAddress(content,neededPage);            }             else if(choice.equals("tel"))            {                clients = clientDao.retrieveUserByTel(content,neededPage);            }            if(session.getAttribute("content") == null)                session.setAttribute("content", content);            //原来session里面没有content和choice的时候就设置，设置过久不用了            if(session.getAttribute("choice")==null)                session.setAttribute("choice", choice);            request.setAttribute("clients", clients);            request.setAttribute("currentPage", String.valueOf(neededPage));   //回传当前页            request.setAttribute("totalPage", String.valueOf(clientDao.getTotalPage()));       //为了实现最后一页            rd = request.getRequestDispatcher("queryResult.jsp");            rd.forward(request, response);                    }        catch(Exception ex){            ex.printStackTrace();        }        finally {            out.close();        }    }

搞完后main页记得记得要清除掉session里面的content，不然悲剧