知识点小结

 if (this.treeView1.SelectedNode.Level>0)
            {
              //判断TreeView选中节点是否为空    
            }

        private void Form1_Load(object sender, EventArgs e)
        {
          //判断xml文件的属性值之经典代码
            Streats str = new Streats();
            TreeNode tn=null;
            XmlDocument doc = new XmlDocument();
            doc.Load("Address.xml");
            XmlNode root = doc.DocumentElement;
            string name = "";
            foreach (XmlNode item in root.ChildNodes)
            {
                if (root.Attributes["name"].Value != name)
                {

                    tn = new TreeNode(root.Attributes["name"].Value);
                    str.StreesName = root.Attributes["name"].Value;
                    list.Add(str);
                    treeView1.Nodes.Add(tn);
                }
                TreeNode tree = new TreeNode(item.Attributes["name"].Value);
                str.JuweiHui = item.Attributes["name"].Value;
                foreach (XmlNode it in item.ChildNodes)
                {
                    TreeNode xx = new TreeNode(it.Attributes["name"].Value);
                    str.Smid = it.Attributes["name"].Value;
                    tree.Nodes.Add(xx);
                    foreach (XmlNode vv in it.ChildNodes)
                    {
                        TreeNode pp = new TreeNode(vv.InnerText);
                        str.Fijname = vv.InnerText;
                        pp.Tag = list;
                        xx.Nodes.Add(pp);
                    }
                }
                tree.Tag = item;
                tn.Nodes.Add(tree);
                name = root.Attributes["name"].Value;
                   
            }
        }

  //01.查询所有年级信息
       public List<Grade> getAllGrades()
       {
           string sql = "select * from grade";
           DataTable dt = SQLHelper.ExecuteDataTable(sql);
           MyTool tool=new MyTool();
           List<Grade> list = tool.DataTableToList<Grade>(dt);
           return list;
       }
你给我一个sql我还你个table

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Student.Model;
using System.Data;
namespace Student.DAL
{
   public  class StudentDAL
    {
       public bool AddStudent(Students stu)
       {
           bool falg = false;
           string sql = @"Insert into Student(Student,LoginPwd,StudentName,Gender,GradeId,Phone,Address,Birthday,Email) values
                     ("+stu.StudentNo+",‘"+stu.LoginPwd+"‘,‘"+stu.StudentName+"‘,‘"+stu.Gender+"‘,"+stu.GradeId+",‘"+stu.Phone+"‘,‘"+stu.Address+"‘,‘"+stu.Birthday+"‘,‘"+stu.Email+"‘,)";
          int a= SQLHelper.ExecuteNonQuery(sql);
          if (a>1)
          {
              falg = true;
          }
          return falg;
       }
       public List<Grade> StudentList()
       {
               //弱类型的DataTable转换成钱类型List<>泛型集合
           string sql = "select *from Grade";
           DataTable dt = SQLHelper.ExecuteDataTable(sql);
           MyTool tool = new MyTool();
           return tool.DataTableToList<Grade>(dt);

       }

    }
}

create procedure Usp_S2227GetInitial
  @gender char(1),
  @sum int Output --输出参数
as
  select *from Student where
  Gender=@gender
  
  select @sum=COUNT(1) from Student where
  Gender=@gender
  
  return 100
  
  
  
  declare @num int
  set @num=0
  
  declare @myReturn int
  set @myReturn=0
  
  exec @myReturn=Usp_S2227GetInitial ‘1‘,@num Output
  print @myReturn
  

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <connectionStrings>
    <add name="contr" connectionString="Data Source=.; Initial CataLog=MySchool;Uid=Sa;"/>
  </connectionStrings>
</configuration>
<!-- App.config配置文件-->

 //Sql注入恒等式   ‘ or 1=1 --

 drop Student 
           where studentid>4

public static string Constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        public static int id;

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace D_018
{
    public class MyTool
    {

        public void GetStudentInsterEx(Student stu)
        {
            string str = "Data Source=.; Initial CataLog=MySchool; Uis=Sa;";

            string sql = "select *from  Student where Student=@Student and StudentPwd=@StudentPwd";
            string sql1 = "usp_GetS2227";
            //自动释放连接对象         
            using (SqlConnection con = new SqlConnection(str))
            {
                SqlCommand cmd = new SqlCommand(sql, con);
                //简易版防注入添加
                cmd.Parameters.Add(new SqlParameter("@StudentName", stu.StudentName));
                con.Open();
                //创建事务
                SqlTransaction tx = new SqlTransaction();
                //绑定的到执行操作
                cmd.Transaction = tx;
                //指定事务类型
                cmd.CommandType = CommandType.StoredProcedure;
                SqlParameter[] p = 
               {
                   //@...要与数据库里面的事务字段一一对应
                   //要求
                   //1.带输入参数的储存过程  性别  char(1)
                   //2.带输出参数的储存过程  统计女生的总人数 @sum
                   //3.带返回值的储存过程    输出储存过程的返回值
                 new SqlParameter("@gender","1"),
                 new SqlParameter("@num",SqlDbType.Int),
                 new SqlParameter("myRetuen",SqlDbType.Int)
               };
                //把值绑定到TextBox中
                //表示为输出参数
                p[1].Direction = ParameterDirection.InputOutput;
                //设置参数为返回值类型
                p[2].Direction = ParameterDirection.ReturnValue;
                //加入到cmd对象中
                cmd.Parameters.AddRange(p);
                int count = Convert.ToInt32(p[1].Value);
                int ret = Convert.ToInt32(p[2].Value);
                //开启事务
                tx = con.BeginTransaction();
                //提交事务
                tx.Commit();
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace D_018
{
    public class MyTool
    {

        public void GetStudentInsterEx(Student stu)
        {
            string str = "Data Source=.; Initial CataLog=MySchool; Uis=Sa;";

            string sql = "select *from  Student where Student=@Student and StudentPwd=@StudentPwd";
            string sql1 = "usp_GetS2227";
            //自动释放连接对象         
            using (SqlConnection con = new SqlConnection(str))
            {
                SqlCommand cmd = new SqlCommand(sql, con);
                //简易版防注入添加
                cmd.Parameters.Add(new SqlParameter("@StudentName", stu.StudentName));
                con.Open();
                //创建事务
                //开启事务
                SqlTransaction tx = con.BeginTransaction();
                //绑定的到执行操作
                cmd.Transaction = tx;
                //指定储存过程类型
                cmd.CommandType = CommandType.StoredProcedure;
                SqlParameter[] p = 
               {
                   //@...要与数据库里面的事务字段一一对应
                   //要求
                   //1.带输入参数的储存过程  性别  char(1)
                   //2.带输出参数的储存过程  统计女生的总人数 @sum
                   //3.带返回值的储存过程    输出储存过程的返回值
                 new SqlParameter("@gender","1"),
                 new SqlParameter("@num",SqlDbType.Int),
                 new SqlParameter("myRetuen",SqlDbType.Int)
               };
                //把值绑定到TextBox中
                //表示为输出参数
                p[1].Direction = ParameterDirection.InputOutput;
                //设置参数为返回值类型
                p[2].Direction = ParameterDirection.ReturnValue;
                //加入到cmd对象中
                cmd.Parameters.AddRange(p);
                int count = Convert.ToInt32(p[1].Value);
                int ret = Convert.ToInt32(p[2].Value);
                
               
                //提交事务
                tx.Commit();
            }
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
namespace MySchool.BLL
{
    //（util）通用工具类
        public class MySchoolBLL
        {
            //MD5加密
            public string MD5GetEx(string name)
            {
                MD5CryptoServiceProvider m = new MD5CryptoServiceProvider();
                byte[] b1 = Encoding.Default.GetBytes(name);
                byte[] b2 = m.ComputeHash(b1);
                string na = string.Empty;
                foreach (byte item in b2)
                {
                    na += item.ToString("x2");
                }
                return na;
            }
            //加密不可逆
            //可以对字符串/文件加密
        }
    }

 MD5 m = new MD5CryptoServiceProvider();
            byte[] a = Encoding.Default.GetBytes("1");
           byte[] b=m.ComputeHash(a);
           StringBuilder sb = new StringBuilder();
           foreach (byte item in b)
           {
               sb.Append(item.ToString("X2"));
           }
           Console.WriteLine(sb.ToString());
           Console.ReadKey();

           //删除光标消失
            int xx = dataGridView1.CurrentRow.Index;
            dataGridView1.Rows[xx].Selected = true;
            dataGridView1.Rows[0].Selected = false;

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <title></title>
        <script src="file/jQuery1.11.1.js" type="text/javascript"></script>
    </head>
        <script>
            $(document).ready(function(){
                var str="www.bdqn";
                str.title="北大青鸟";
                alert(str.substring (4));
            });
        </script>
    <body>        
    </body>
</html>

select *from Room
select *from RoomType
select *from RoomState
select RoomID,BedNUm,RoomStateName,TypeName,Description ,GuestNum,TypeID
from RoomType,Room,RoomState
where Room.RoomStateID=RoomState.RoomStateID and RoomTypeID=RoomType.TypeID
insert into Room(BedNum,RoomStateID,RoomTypeID,Description,GuestNum) values(10,2,13,‘ing送的‘,0)
update Room set BedNum=20,RoomTypeID=19,Description=‘ing房子‘ where RoomID=26
select RoomID, Convert(varchar(2),RoomID)+ ‘号房(床位:‘ +Convert(varchar(2),(BedNum-GuestNum)) + cast(‘)‘ as varchar(20)) as description from Room where BedNUm>GuestNum
delete Room where RoomID=26
select *from ResideState
select *from GuestRecord
delete GuestRecord where GuestID=8
insert into GuestRecord(IdentityID,GuestName,RoomID,ResideID,ResideDate,Deposit) 
values (112313123,‘灰太狼‘,6,1,‘2012-2-3‘,2000)
update Room set GuestNum+=1 where RoomID=6

select GuestName,Identityid,ResideDate,Deposit,ResideName,LeaveDate,TotalMoney,Room.RoomID,TypeName,RoomStateName,GuestId
from RoomType,Room,GuestRecord,RoomState,ResideState
where RoomType.TypeID=Room.RoomTypeID and RoomState.RoomStateID=Room.RoomStateID 
and Room.RoomID=GuestRecord.RoomID and ResideState.ResideId=GuestRecord.ResideID
and ResideDate between Convert(datetime,‘2011-02-12 16:50:00.000‘) and Convert(datetime,‘2013-09-01 10:47:00.000‘)
and GuestRecord.ResideID=1
select RoomId from Room where RoomTypeID=13

SELECT 
 a.RoomID,
                            a.BedNum,
                            a.RoomStateID,
                            a.Description,
                            a.GuestNum,
                            a.RoomTypeID,
                            b.TypeName,
                            b.TypePrice,
                            c.RoomStateName
                            FROM [Room] a INNER JOIN [RoomType] b ON a.RoomTypeID = b.TypeID
                            INNER JOIN [RoomState] c ON a.RoomStateID = c.RoomStateID
                            WHERE 1=1 

表示层exe 业务逻辑层dll  数据访问层dll

E:\apache-tomcat-7.0.77\work\Catalina\localhost\AA\org\apache\jsp

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.77
 * Generated at: 2017-07-20 02:28:50 UTC
 * Note: The last modified time of this file was set to
 *       the last modified time of the source file after
 *       generation to assist with modification tracking.
 */
package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {

  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();

  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;

  private volatile javax.el.ExpressionFactory _el_expressionfactory;
  private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  }

  public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
    if (_el_expressionfactory == null) {
      synchronized (this) {
        if (_el_expressionfactory == null) {
          _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
        }
      }
    }
    return _el_expressionfactory;
  }

  public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
    if (_jsp_instancemanager == null) {
      synchronized (this) {
        if (_jsp_instancemanager == null) {
          _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
        }
      }
    }
    return _jsp_instancemanager;
  }

  public void _jspInit() {
  }

  public void _jspDestroy() {
  }

  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
        throws java.io.IOException, javax.servlet.ServletException {

    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;


    try {
      response.setContentType("text/html;charset=utf-8");
      pageContext = _jspxFactory.getPageContext(this, request, response,
                  null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write(‘\r‘);
      out.write(‘\n‘);

String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

      out.write("\r\n");
      out.write("\r\n");
      out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
      out.write("<html>\r\n");
      out.write("  <head>\r\n");
      out.write("    <base href=\"");
      out.print(basePath);
      out.write("\">\r\n");
      out.write("    \r\n");
      out.write("    <title>My JSP ‘index.jsp‘ starting page</title>\r\n");
      out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
      out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
      out.write("\t<meta http-equiv=\"expires\" content=\"0\">    \r\n");
      out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
      out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
      out.write("\t<!--\r\n");
      out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
      out.write("\t-->\r\n");
      out.write("  </head>\r\n");
      out.write("  \r\n");
      out.write("  <body>\r\n");
      out.write("      今天天气不错\r\n");
      out.write("      ");

     String info= request.getRemoteAddr()+ "\t"+request.getRemoteUser();
      System.out.println(info);
      
      out.write("\r\n");
      out.write("  </body>\r\n");
      out.write("</html>\r\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

 <%
      String info= request.getRemoteAddr()+ "\t"+request.getRemoteUser();
      System.out.println(info);
      %>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

1.什么内置对象  不用new  直接用

2.request.setResuqestDisponse().forname()转向
request.getParamper();获取属性
resquest.setAttbrite()设置属性
resquest.getParamperValues();

3.response.sendRedrist();重定向



4          转发   重定向    
请求次数   1       2
url地址    不变    变
站内站外   站内   站外
资源共享   共享   不共享
5.保存在服务器端的一次请求N次相应的过程

6.session.setAttbrite("name",name);


7.<%@ page import="java.util.*" lanauge="html/text" pageEncoding="utf-8" %>
  

8小脚本
  注释
  表达式

在我们在myeclips里使用junit测试工具时有时会遇到错误，这是什么原因呢？
导致问题的原因通常有下面几个:

(1)没有导入jar包
(2)导入jar包版本太低
(3)注意@Test要写在方法上面
即使报错  但是  Test单词只要变成灰色就能用因为你还没有写测试方法

jsp 页面  500报错  该 大写的 UTF-8   localhost

 <!--声明出去的是全局变量 -->
    <%!
    
    int a=1;
    %>
    <%=a++ %>

<!-- 它是jsp指令，也是一种特殊的标签！ -->  
<%@ page language="java" contentType="text/html; charset=utf-8"  
    pageEncoding="utf-8"%>  
 <%  
    //获取项目名  
    String path = request.getContextPath();  
    //http://localhost:8080/项目名/  
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
 %>  
<!DOCTYPE html ">  
<html>  
<head>  
    <!-- 向页面输出basePath，但只能在查看源文件里面显示值 -->  
    <base href="<%=basePath %>">  
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">  
<title>Jsp基本内容</title>  
</head>  
<body>  
    <%  
        //java代码片段(常用)，用于定义0~N条Java语句！方法内能写什么，它就可以放什么！  
        int a = 10;//是局部变量  
    %>  
    <%  
        out.print(a++);//永远输出10，因为没有this那a就是局部变量  
    %>  
    <%=a %><!-- 作用和out.print(a)一样 ，因为上面输出a后a加了1所以永远输出11，无论刷新多少次-->  
      
    <!-- 下面这个a是全局变量 -->  
    <%!  
        int a=100;  
        public void fun1(){  
            System.out.println(a);  
        }  
    %>  
    <%  
        out.print(this.a++);//调用的是声明的那个变量a，页面输出值,因为 这个a是全局变量，所以刷新页面原来的值还在  
        fun1();//控制台输出  
    %>  
</body>  
</html>  

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%-- <%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> --%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <%-- <base href="<%=basePath%>"> --%>
    
    <title>登陆</title>
    
    
  </head>
  
  <body>
  <!-- 报错的原因把上面的注释掉 -->
   <%@ include file="index.jsp" %>
   <%
    int i=7;
    int j=10;
   %>
  </body>
</html>

前缀运算符的运算规则是先运算后引用，所以，此题输出结果为Count：2

在JSP中的注释一共分为两种注释：
显式注释：在HTML中存在注释“<!--注释内容 -->”
隐式注释：可以使用java中的“//”、“/*….*/”，以及JSP中自己的注释：“<%-- 注释内容 --%>”

//分页查询
    public List<News> findAll(int pageIndex,int pageSize) throws Exception{
        String sql="select top "+pageSize+" * from news where nid not in(select top "+(pageIndex-1)*pageSize+" nid from news )";
        //top后面不能跟变量
        //String sql="select top ? * from news where nid not in(select top ? nid from news )";
        //Object[] p={pageSize,(pageIndex-1)*pageSize};
        ResultSet rs=executeQuery(sql);
        List<News> list=new ArrayList<News>();
       while(rs.next()){
           News news=new News();
           news.setNititle(rs.getString("nititle"));
           news.setNcreatedate(rs.getString("string"));
           list.add(news);
       }
       return list;    
    }

SELECT * FROM news WHERE  ntid=15 OR ntid=16 AND nid >=(1-1)*3  LIMIT 0,3 
mysql  多条件分页查询   下标,总数据数

        //静态方法不可以直接访问实例成员
        //实例方法可以直接访问静态成员

            // 1. 默认三条数据
            int pageSize = 3;
            page.setPageSize(3);

            // 2. 总页数
            int mytotalpages = 0;
            try {
                mytotalpages = service.getAllCount() % pageSize == 0 ? service
                        .getAllCount() / pageSize : service.getAllCount()
                        / pageSize + 1;
            } catch (Exception e2) {
            }
            page.setTotalPages(mytotalpages);

            // 3. 默认当前页
            int myindex = 1;
            String pageIndex = request.getParameter("pageIndex");

            // 解决页初加载时为null的问题
            if (pageIndex != null && (!pageIndex.equals(""))) {
                myindex = Integer.parseInt(pageIndex);
            }
            if(myindex>mytotalpages){
                myindex=1;
            }
            if(myindex<1){
                myindex=1;
            }
            System.out.println("当前页"+myindex+"\n"+"总页数"+mytotalpages);
            // 当前页赋值
            page.setPageIndex(myindex);

            
            
            // 4 泛型集合
            try {
                //获取当前的新闻编号
                String ntid=request.getParameter("ntid");
                request.setAttribute("topicid", ntid);
                System.out.println("储存当前新闻编号"+(String)request.getAttribute("topicid"));            
                List<News> xx = service.getOneNewsData(page.getPageIndex(),pageSize,ntid);
                page.setList(xx);

            } catch (Exception e1) {
                e1.printStackTrace();
            }
           
            // 5. 放到作用域中
            request.setAttribute("list", page);
               
            // 6.加载新闻主题
            ITopicService topic=new TopicServiceImpl();
            try {
                List<Topic> topicList=topic.findAll();
                request.setAttribute("topicList",topicList);
            } catch (Exception e) {
            }
            // 7. 转发到index.jsp
            request.getRequestDispatcher("/index.jsp").forward(request,
                    response);

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  
    <base href="<%=basePath%>">
    
    <title>欢迎</title>
    <script type="text/javascript">
      var request=new XMLHttpRequest();
      request.open("GET", getphp, true);
      request.send();//放了一些数据
      request.onreadystatechange=function(){//对过程进行了间监听
          if(request.readyState==4&&request.status===200)
              request.responseText
      }
      </script>
  </head>
  
  <body>
    
  </body>
</html>

获取相同属性名的表单
if  判断  只要有一个符合条件就不在往下进行

<jsp:include page="包含的页面" />为动态包含,即所包含的页面是独立包含,主与子页面互不影响

<%@ include file="包含的页面" %> 为静态包含,即所包含的页面是父页面的子,做为父页面的一部分来调用,会共享父页面的变量

java快捷键
syst+Alt+/=打印方法名

下面举个生活中的实例来说明：
请求重定向：就好比我们找一个A广告公司给设计名片，A明确告诉我们他们不会设计，就让我们找B公司，结果B公司给我设计好了，所以我们会对外宣称是B公司给我们设计的名片，（所以我们就相当于发送了两次次请求，URL地址栏里就从A变成了B公司）
请求转发：同样去找A公司给设计名片，A公司虽然不能设计但是他们接下了我们的活，把这项任务外包（转发）给B公司，最终我们会把钱给A公司，也就会对外宣称是A公司给我们设计的名片这就是请求重定向（所以我们就相当于只对A发送了一次请求，URL地址栏里依然是A公司）。

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions"  prefix="fn" %>
用El表达式截取字符串

1. ${fn:substring("你要截取的字符串"),beginIndex,endIndex}   

 <%=item.getContent().substring(0, 3) %>...

先给大家介绍下MyBatis中#{}和${}的区别，具体介绍如下：
1. #将传入的数据都当成一个字符串，会对自动传入的数据加一个双引号。如：order by #user_id#，如果传入的值是111,那么解析成sql时的值为order by "111", 如果传入的值是id，则解析成的sql为order by "id".
2. $将传入的数据直接显示生成在sql中。如：order by $user_id$，如果传入的值是111,那么解析成sql时的值为order by user_id, 如果传入的值是id，则解析成的sql为order by id.
3. #方式能够很大程度防止sql注入。　
4.$方式无法防止Sql注入。
5.$方式一般用于传入数据库对象，例如传入表名.
6.一般能用#的就别用$.
MyBatis排序时使用order by 动态参数时需要注意，用$而不是#
字符串替换
默认情况下，使用#{}格式的语法会导致MyBatis创建预处理语句属性并以它为背景设置安全的值（比如?）。这样做很安全，很迅速也是首选做法，有时你只是想直接在SQL语句中插入一个不改变的字符串。比如，像ORDER BY，你可以这样来使用：
ORDER BY ${columnName}
这里MyBatis不会修改或转义字符串。
重要：接受从用户输出的内容并提供给语句中不变的字符串，这样做是不安全的。这会导致潜在的SQL注入攻击，因此你不应该允许用户输入这些字段，或者通常自行转义并检查。

   <!--内存级别的分页-->
    <select id="RowBound" parameterType="map" resultType="dept">
        select * from dept
    </select>

   //内存级别的分页
    public List<Dept> RowBound(int num1 ,int num2 );
   @Test//内存级别的分页(逻辑分页)
    public void RowsRound() throws Exception {
        List<Dept> list = MyBatisUtil.getSqlSession().selectList("RowBound",  new RowBounds(1, 3));
        for (Dept item : list) {
                System.out.println(item.getDeptName());
        }
    }