第75节：Java中的JSP,EL和JSTL
哭吧看不完的!!!
Cookie和`Session
请求转发和重定向的区别:
- 地址不一样
- 请求次数也不一样
- 数据无法传递
4.跳转范围有限制 - 效率
请求转发请求1次,只能对当前项目跳转,重定向请求2次.重定向是无法传递的,重定向对跳转范围没有限制.
Cookie是服务器发送给客户端,存储在客户端的小数据.发送cookie:
Cookie cookie = new Cookie("key", value");
response.addCookie(cookie);
服务器返回cookie给客户端
// 响应头
Set-Cookie: a=b
接收cookie
Cookie[] cookies = request.getCookies();
客户端提交数据的cookie
// Cookie: a=b;c=d;
Cookie分会话cookie和持久cookie
关闭cookie,可以关闭浏览器.
持久的cookie,在一段时间内有效
Cookie cookie = new Cookie("a","b");
cookie.setMaxAge(); // 秒
response.addCookie(cookie);
cookie.setDomain(".dashucoding.com");
// 只有带上这个域名的时候,才会有cookie
// 例如:www.dashucoding.com
cookie..setPath("/Demo");
// 要进行访问上面的路径才会带cookie
http://localhost:8080/Demo
移除cookie
Cookie cookie = new Cookie("a","b");
cookie.setMaxAge(60*60*24);
response.addCookie(cookie);
// 获取以前cookie,设置有效期
Cookie[] cookies = request.getCookies();
Cookie cookie = CookieUtil.findCookie(cookies,"a");
cookie.setMaxAge(0);
reponse.addCookie(cookie);
cookie是存在客户端的.
可以创建一个新的cookie去替换
Cookie cookie = new Cookie("a","dashu");
cookie.setMaxAge(0);
response.addCookie(cookie);
Session是基于Cookie的一种会话技术.cookie的安全隐患,是把数据存放在客户端,下次访问时,带上这个数据,服务端就知道客户端是谁.
Session的数据是存放在服务端.
session对应sessionid传递给客户端,是通过cookie传递的.只要有sessiondi,就可以获取以前的数据.
HttpSession session = request.getSession();
session.setAttribute();
sesssion.getAttribute();
package com.dashucoding.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class Demo01
*/
public class Demo01 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
HttpSession session = request.getSession();
// 得到会话ID
session.getId();
// 存值
//session.setAttribute(name, value);
// 取值
//session.getAttribute(name);
// 移植
//session.removeAttribute(name);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
session创建:
request.getSession
销毁
关闭服务器,或自动会话过期,默认时间为30分钟.
在进行访问浏览器时,再次重启是无法获取以前的数据的,因为
sessionid是通过cookie来传递的,cookie没有设置有效期,关闭后,就cookie删除了,同时cookie带过来sessionid同样也没有了.
手动设置cookie
String id = request.getSession().getId();
Cookie cookie = new Cookie("JSESSIONID",id);
cookie.setMaxAge(60*60*24*7);
response.addCookie(cookie);
JSP和EL和JSTL
什么是JSP
JSP就是一个网页而已,或者是一个Java类,继承了servlet,所以jsp是一个servlet.
jsp设计目的是因为html是显示静态内容,有时网页要一些动态数据.html是不支持java代码,jsp支持java代码.
写法
指令
<%@ %>
language
contentType内容类型
content-Type="text/html;charset=UTF-8"
pageEncoding jsp内容编码
extends="httpjspbase"
用于指定jsp翻译成java文件后,继承的父类是谁
import导包使用,一般不用手写
session
true or false
errorPage 错误的页面.
isErrorPage="true" 显示错误
errorPage="error.jsp" 呈现错误
errorPage 值需要给错误的页面路径
include
<%-- <%@ include file="other02.jsp"%> --%>
把另外一个页面的内容拿过来
<%-- <%@ taglib prefix="" uri=""%> --%>
url标签库的路径
prefix别名
include和forward
<%--
<jsp:include page=""></jsp:include>
<jsp:param value="" name=""/>
<jsp:forward page=""></jsp:forward> --%>
<%-- <jsp:include page="other02.jsp"></jsp:include> --%>
<%-- <jsp:forward page="other02.jsp"></jsp:forward>
等同于以下代码 --%>
<%
//请求转发
//request.getRequestDispatcher("other02.jsp").forward(request, response);
%>
<jsp:forward page="other02.jsp">
<jsp:param value="beijing" name="address"/>
</jsp:forward>
jsp: param
<jsp:forward page="other02.jsp">
<jsp:param value="beijing" name="address"/>
</jsp:forward>
<%= request.getParameter("address")%>
小结
什么是JSP
为什么会有JSP
三大指令集
page
有什么用,那么怎么用,有哪些常用的属性
include
有什么用,那么怎么用
taglib
有什么用,怎么用
JSP动作标签
jsp:forword
jsp:include
jsp:param
jsp的内置对象
四个作用域
pageContext
request
session
appiication
JSP内置对象
内置对象是在jsp页面中使用的这些对象,不用创建
pageContext
request
session
application
exception
out
page
config
response
application: ServletContext
config: ServletConfig
out: JspWriter
page: Object
pageContext: PageContext
request: HttpServletRequest
session: HttpSession
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;
request, response
四个作用域
pageContext
request
session
application
作用域,就是这个对象可以在哪用,对象可以存值,取值范围限定.
作用的对象是不一样的
setAttribute
getAttribute
pageContext:作用域只能在当前页面,PageContext
request:作用域限于一次请求
只要服务器做出反应,域中的值就没有了HttpServletRequest
session:限于一次会话,第二次会话就没了,HttpSession
application:都有,都可以访问,只有服务器关闭后就不能访问了.->ServletContext
一个工程只能有一个
exception -> Throwable
config -> ServletConfig
page -> Object -> 当前类的实例
response -> HttpServletResponse
out JSP -> JSPWriter
out
response.getWriter
out对象输出的内容是放到response的缓冲区内的,先输出response本身的内容,然后才是out里面的内容.
exception -> Throwable
page -> Object -> 一般就是jsp翻译成java类的实例对象 -> this -> 当前实例类
config -> ServletConfig
out -> JspWriter
response -> HttpServletResponse
pageContext -> PageContext: 作用域当前页面
request -> HttpServletReques: 作用域限于一次请求
session -> HttpSession -> 作用域限于一次会话
application -> ServletContext
整个工程可以访问,服务器关闭后就不能进行访问了
pageContext 也可以获取其他8个内置对象
EL表达式:
是什么,怎么用,也有内置对象?
// 作用域
pageScope
requestScope
sessionScope
applicationScope
// 请求头
header
headerValues
参数
param
params
EL表达式
简化jsp中java的代码.
${ 表达式 }
取值方式:
<%
String [] a = {"aa","bb","cc","dd"};
pageContext.setAttribute("array", a);
%>
<%
User user = new User {"zhangsan",18};
session.setAttribute("u", user);
%>
${u.name}, ${u.age}
<%@page import="com.dashucoding.domain.User"%>
<%@ 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>
从域中取值。 得先存值。
<%
//pageContext.setAttribute("name", "zhangsan");
session.setAttribute("name", "lisi...");
%>
<br>直接指定说了，到这个作用域里面去找这个name<br>
${ pageScope.name }
<br>//先从page里面找，没有去request找，去session，去application <br>
${ name }
<br>指定从session中取值<br>
${ sessionScope.name }
<br>---------------------------------------------<br>
<%
User user = new User("zhangsan",18);
session.setAttribute("u", user);
%>
${ u.name } , ${ u.age }
${ a > b}
${ a gt b }
${ empty u }
</body>
</html>
package com.dashucoding.domain;
public class User {
private String name;
private int age;
public User(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
<%@page import="java.util.HashMap"%>
<%@page import="java.util.Map"%>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ 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>
<%
pageContext.setAttribute("name", "page");
request.setAttribute("name", "request");
session.setAttribute("name", "session");
application.setAttribute("name", "application");
%>
按普通手段取值<br>
<%= pageContext.getAttribute("name")%>
<%= request.getAttribute("name")%>
<%= session.getAttribute("name")%>
<%= application.getAttribute("name")%>
<br>使用EL表达式取出作用域中的值<br>
${ pageScope.name }
${ requestScope.name }
${ sessionScope.name }
${ applicationScope.name }
${name }
<br>-----------------------------<br>
<%
String [] a = {"aa","bb","cc","dd"};
pageContext.setAttribute("array", a);
%>
使用EL表达式取出作用域中数组的值<br>
${array[0] } , ${array[1] },${array[2] },${array[3] }
<br>-------------集合数据----------------<br>
<%
List list = new ArrayList();
list.add("11");
list.add("22");
list.add("33");
list.add("44");
//pageContext.setAttribute("li", list);
session.setAttribute("li", list);
%>
使用EL表达式取出作用域中集合的值<br>
${li[0] } , ${li[1] },${li[2] },${li[7] }
<br>-------------Map数据----------------<br>
<%
Map map = new HashMap();
map.put("name", "zhangsna");
map.put("age",18);
map.put("address","北京..");
map.put("address.aa","深圳..");
//pageContext.setAttribute("map", map);
application.setAttribute("m", map);
%>
使用EL表达式取出作用域中Map的值<br>
${applicationScope.m.name } , ${m.age } , ${m.address } , ${m["address.aa"] }
</body>
</html>
EL表达式隐式对象
11个内置对象
${ }
pageCotext
pageScope
requestScope
sessionScope
applicationScope
请求参数
param
paramValues
请求头
header
headerValues
cookie
initParam初始化参数
pageContext是PageContext实例,其他都是Map类.
EL内置对象
// 作用域
pageScope
requestScope
sessionScope
applicationScope
// 请求头
header
headerValues
// 请求参数
param
params
cookie
全局初始化参数
initparam
pageContext
引入
<%@ 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>
这是el03页面
<jsp:forward page="el04.jsp">
<jsp:param value="beijing...." name="address"/>
</jsp:forward>
</body>
</html>
<%@ 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>
这是el04页面<br>
<%=request.getParameter("address") %>
<br>
使用EL表达式获取这个参数
<%-- response.addCookie(new Cookie("name","value"));
${cookie.name } --%>
${param.address }
</body>
</html>
小结案例
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" %>
<%-- <%@ include file="other02.jsp"%> --%>
<%-- <%@ taglib prefix="" uri=""%> --%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%-- <jsp:include page="other02.jsp"></jsp:include> --%>
这是other页面的内容.
</body>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" isErrorPage="true"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>这是other022222的内容</h3>
<br>收到的参数是：<br>
<%= request.getParameter("address")%>
<%
%>
</body>
</html>
<%@ 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>
这是other03的页面
<br>使用作用域来存储数据<br>
<%
pageContext.setAttribute("name", "page");
request.setAttribute("name", "request");
session.setAttribute("name", "session");
application.setAttribute("name", "application");
%>
取出四个作用域中的值<br>
<%=pageContext.getAttribute("name")%>
<%=request.getAttribute("name")%>
<%=session.getAttribute("name")%>
<%=application.getAttribute("name")%>
<!-- //跳转到下一个界面去了 -->
<%
//请求转发. 一次请求
//request.getRequestDispatcher("other04.jsp").forward(request, response);
//重定向 2次请求
response.sendRedirect("other04.jsp");
%>
</body>
</html>
<%@ 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>
<h3>这是04的页面</h3><br>
取出四个作用域中的值<br>
<%=pageContext.getAttribute("name")%>
<%=request.getAttribute("name")%>
<%=session.getAttribute("name")%>
<%=application.getAttribute("name")%>
</body>
</html>
<%@ 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>
这是other05的页面<br>
<%
out.write("这是使用out对象输出的内容");
%>
<br>
<%
response.getWriter().write("这是使用response对象输出的内容");
%>
</body>
</html>
<%@ 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>
<%--
<jsp:include page=""></jsp:include>
<jsp:param value="" name=""/>
<jsp:forward page=""></jsp:forward> --%>
这是jsp_action的页面.
<%-- <jsp:include page="other02.jsp"></jsp:include> --%>
<%-- <jsp:forward page="other02.jsp"></jsp:forward>
等同于以下代码 --%>
<%
//请求转发
//request.getRequestDispatcher("other02.jsp").forward(request, response);
%>
<jsp:forward page="other02.jsp">
<jsp:param value="beijing" name="address"/>
</jsp:forward>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" isErrorPage="true"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
服务器正在维护，请稍后访问..
<%-- <%=exception.toString() %> --%>
</body>
</html>
<%@page import="java.util.HashMap"%>
<%@page import="java.util.Map"%>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ 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>
<%
pageContext.setAttribute("name", "page");
request.setAttribute("name", "request");
session.setAttribute("name", "session");
application.setAttribute("name", "application");
%>
按普通手段取值<br>
<%= pageContext.getAttribute("name")%>
<%= request.getAttribute("name")%>
<%= session.getAttribute("name")%>
<%= application.getAttribute("name")%>
<br>使用EL表达式取出作用域中的值<br>
${ pageScope.name }
${ requestScope.name }
${ sessionScope.name }
${ applicationScope.name }
${name }
<br>-----------------------------<br>
<%
String [] a = {"aa","bb","cc","dd"};
pageContext.setAttribute("array", a);
%>
使用EL表达式取出作用域中数组的值<br>
${array[0] } , ${array[1] },${array[2] },${array[3] }
<br>-------------集合数据----------------<br>
<%
List list = new ArrayList();
list.add("11");
list.add("22");
list.add("33");
list.add("44");
//pageContext.setAttribute("li", list);
session.setAttribute("li", list);
%>
使用EL表达式取出作用域中集合的值<br>
${li[0] } , ${li[1] },${li[2] },${li[7] }
<br>-------------Map数据----------------<br>
<%
Map map = new HashMap();
map.put("name", "zhangsna");
map.put("age",18);
map.put("address","北京..");
map.put("address.aa","深圳..");
//pageContext.setAttribute("map", map);
application.setAttribute("m", map);
%>
使用EL表达式取出作用域中Map的值<br>
${applicationScope.m.name } , ${m.age } , ${m.address } , ${m["address.aa"] }
</body>
</html>
JSTL介绍
jstl是什么,用来做什么.
el只能取值操作
jstl遍历的效果
jstl. jsp standard tag library jsp标签库
简化jsp,与el表达式配合
// 使用jstl
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:set var = "name" value="dashu"></c:set>
${name}
<c:set var = "name" value="dashu" scope="session"></c:set>
${sessionScope.name}
默认存储的是page
<c:set var = "age" value="12" ></c:set>
<c:if text="${age>10}">
age大于10
</c:if>
<c:forEach begin="1" end="10" var="i" step="2">
${i}
</c:forEach>
学生信息管理系统
login.jsp -> 一个页面
login_servlet -> 一个页面
基本操作页面 -> 查看学生列表
stu_list.jsp
获取信息
查询数据库
判断账号信息
正确前往下一页
错误,登录失败
案例:
package com.dashucoding.dao;
import java.util.List;
import com.dashucoding.domain.Student;
public interface StuDao {
/**
* 查询出来所有的学生信息
* @return List集合
*/
List<Student> findAll();
}
package com.dashucoding.dao;
/*
* 定义
* 该Dao定义了对用户表的访问规则
* */
public interface UserDao {
/**
* 这里简单就返回一个Boolean类型， 成功或者失败即可。
*
* 但是开发的时候，登录的方法，一旦成功。这里应该返回该用户的个人信息
* @param userName
* @param password
*
* @return true : 登录成功， false : 登录失败。
*/
boolean login(String userName , String password);
}
package com.dashucoding.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.dashucoding.dao.StuDao;
import com.dashucoding.domain.Student;
import com.dashucoding.util.JDBCUtil;
public class StuDaoImpl implements StuDao{
@Override
public List<Student> findAll() {
List<Student> list = new ArrayList<Student>();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
//1. 得到连接对象
conn = JDBCUtil.getConn();
String sql = "select * from t_stu";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
//数据多了，用对象装， 对象也多了呢？ 用集合装。
while(rs.next()){ //10 次 ，10个学生
Student stu = new Student();
stu.setId(rs.getInt("id"));
stu.setAge(rs.getInt("age"));
stu.setName(rs.getString("name"));
stu.setGender(rs.getString("gender"));
stu.setAddress(rs.getString("address"));
list.add(stu);
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
JDBCUtil.release(conn, ps, rs);
}
return list;
}
}
package com.dashucoding.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.dashucoding.dao.UserDao;
import com.dashucoding.util.JDBCUtil;
public class UserDaoImpl implements UserDao {
@Override
public boolean login(String userName , String password) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
//1. 得到连接对象
conn = JDBCUtil.getConn();
String sql = "select * from t_user where username=? and password=?";
//2. 创建ps对象
ps = conn.prepareStatement(sql);
ps.setString(1, userName);
ps.setString(2, password);
//3. 开始执行。
rs = ps.executeQuery();
//如果能够成功移到下一条记录，那么表明有这个用户。
return rs.next();
} catch (SQLException e) {
e.printStackTrace();
}finally {
JDBCUtil.release(conn, ps, rs);
}
return false;
}
}
package com.dashucoding.domain;
public class Student {
private int id ;
private String name;
private int age ;
private String gender;
private String address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
package com.dashucoding.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.dashucoding.dao.StuDao;
import com.dashucoding.dao.UserDao;
import com.dashucoding.dao.impl.StuDaoImpl;
import com.dashucoding.dao.impl.UserDaoImpl;
import com.dashucoding.domain.Student;
/**
* Servlet implementation class LoginServlet
*/
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
// 提交的数据有可能有中文
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=utf-8");
// 获取客户端提交的信息
String userName = request.getParameter("username");
String password = request.getParameter("password");
// 去访问dao ， 看看是否满足登录
UserDao dao = new UserDaoImpl();
boolean isSuccess = dao.login(userName, password);
if (isSuccess) {
// response.getWriter().write("登录成功.");
// 请求转发
// 查询所有的学生信息
StuDao stuDao = new StuDaoImpl();
List<Student> list = stuDao.findAll();
// 先把这个集合存到作用域
request.getSession().setAttribute("list", list);
// 重定向
response.sendRedirect("stu_list.jsp");
} else {
response.getWriter().write("用户名或者密码错误！");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
package com.dashucoding.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password= null;
static{
try {
//1. 创建一个属性配置对象
Properties properties = new Properties();
// InputStream is = new FileInputStream("jdbc.properties");
//使用类加载器，去读取src底下的资源文件。 后面在servlet
InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
//导入输入流。
properties.load(is);
//读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 获取连接对象
* @return
*/
public static Connection getConn(){
Connection conn = null;
try {
Class.forName(driverClass);
//静态代码块 ---> 类加载了，就执行。 java.sql.DriverManager.registerDriver(new Driver());
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//DriverManager.getConnection("jdbc:mysql://localhost/test?user=monty&password=greatsqldb");
//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
conn = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
/**
* 释放资源
* @param conn
* @param st
* @param rs
*/
public static void release(Connection conn , Statement st , ResultSet rs){
closeRs(rs);
closeSt(st);
closeConn(conn);
}
public static void release(Connection conn , Statement st){
closeSt(st);
closeConn(conn);
}
private static void closeRs(ResultSet rs){
try {
if(rs != null){
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
rs = null;
}
}
private static void closeSt(Statement st){
try {
if(st != null){
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
st = null;
}
}
private static void closeConn(Connection conn){
try {
if(conn != null){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
conn = null;
}
}
}
<%@ 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>
<h2>欢迎学生管理系统</h2>
<form action="LoginServlet" method="post">
账号: <input type="text" name="username" /><br>
密码: <input type="password" name="password" /><br>
<input type="submit" value="登录">
</form>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生信息管理系统</title>
</head>
<body>
<br>学生列表<br>
<table border="1" width="700">
<tr align="center">
<td>编号</td>
<td>姓名</td>
<td>年龄</td>
<td>性别</td>
<td>住址</td>
<td>操作</td>
</tr>
<c:forEach items="${list}" var="stu">
<c:if test=""></c:if>
<tr align="center">
<td>${stu.id }</td>
<td>${stu.name }</td>
<td>${stu.age }</td>
<td>${stu.gender }</td>
<td>${stu.address }</td>
<td><a href="#">更新</a> <a href="#">删除</a></td>
</tr>
</c:forEach>
</table>
</body>
</html>
分析
login.jsp -> LoginServlet -> 获取登录信息
创建用户表,
创建UserDao
创建UserDaoImple
LoginServlet里面访问UserDao,判断登录,
创建stu_list.jsp,让登录进入
创建学生表
定义Dao,StuDao
StuDao, StuDaoImpl
数据库
小结
jsp
JSP -> 九个内置对象
page
include
taglib
<jsp:include>
<jsp:forward>
<jsp:param>
EL -> 11个内置对象
${ 表达式 }
取4个作用域中的值
pageContext
pageScope
requestScope
sessionScope
applicationScope
header
headerValues
param
paramValues
cookie
initParam
JSTL
<c:set>
<c:if>
<c:forEach>
如果看了觉得不错
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