JSP基础及el表达式和JSTL表达式
什么是JSP?
全称 Java Server Page 中文名 JAVA服务器页面
由Sun Microsystems公司倡导 许多公司参与一起建立的一种动态网页技术标准
JSP 原理
访问jsp页面时 jsp页面会被翻译成.java文件
然后 .java会被编译成 .class文件(字节码文件)
在网页中显示当前时间
<%@ page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
// 正常写 Java 代码
Date date = new Date();
out.print(date.toLocaleString());
// 被废弃的方法,使用仅为测试
%>
body>
html> 实现登录页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<form action="/Demo/dologin.jsp" method="post">
账号:<input type="text" name="username">
<br>
密码:<input type="password" name="password">
<br>
<input type="submit" value="登录">
<br>
<%
String msg = (String)request.getAttribute("msg");
if(msg != null){
out.print(msg);
}
%>
form>
body>
html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
// 获取参数
String username = request.getParameter("username");
String password = request.getParameter("password");
// 处理逻辑
if(username.equals("test") && password.equals("123")){
// 登录成功
// 跳转页面 -> 欢迎页面,并且显示名字
// 传值时,如果是非表单提交的数据,可以保存在域对象中
// 如果是表单提交过来的数据,直接使用请求转发就行了
request.getRequestDispatcher("/success.jsp").forward(request, response);
} else {
// 登录失败 返回登录页面
// 相对于服务器内,不用添加工程名,例如:请求转发
// 相对于服务器外(相对于网址的8080后),需要添加工程名,例如:请求重定向
// 失败后,在页面中显示错误信息
// 使用请求转发,比较合适
request.setAttribute("msg", "登录失败,请确认用户名和密码!");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
// 跳转页面
%>
body>
html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
response.setContentType("text/html;charset=UTF-8");
request.setCharacterEncoding("UTF-8");
%>
<h1>欢迎你
<%
// String username = (String)session.getAttribute("username");
String username = request.getParameter("username");
out.write(username);
%>
h1>
body>
html><%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page session="true" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%-- jsp注释:安全效率高 --%>
<%!
// 加上叹号会被翻译到类的下面,即为全局变量
// 还可以声明方法,静态块
// 可以这么用,但是一般没人这么去写!
int num2 = 10;
%>
<%
// 测试session开关
session.getAttribute("123123");
int num1 = 10;
num1++;
num2++;
// out.print(num1);
%>
<%=num1+2 %>
<%=num2 %>
body>
html><%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page errorPage="/error.jsp" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
int num = 10 / 0;
%>
body>
html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page isErrorPage="true" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
String msg = exception.getMessage();
out.print(msg);
%>
服务器正在紧张的建设当中...请稍后重试
body>
html><%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%--@ include file="/4.jsp" --%>
<%-- "/4.jsp" > --%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<c:if test="">c:if>
bbbbbb
body>
html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
aaaaaaaa
body>
html><%@ page import="Demo.User"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
"-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
"Content-Type" content="text/html; charset=UTF-8">
Insert title here
<%
// 创建一个User对象
User user = new User();
user.setName("wanglong");
user.setPwd("123");
out.print(user.getName());
%>
"user1" class="Demo.User">
<%-- "user1" class="Demo.User"/> --%>
"name" name="user1" value="dingpeng" />
"pwd" name="user1" value="456" />
<%=user1 %>
"name" name="user1"/>
"pwd" name="user1"/>
public class User {
private String name;
private String pwd;
public User() {
super();
}
public User(String name, String pwd) {
super();
this.name = name;
this.pwd = pwd;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
@Override
public String toString() {
return "User [name=" + name + ", pwd=" + pwd + "]";
}
} pageContext 域
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>转发title>
head>
<body>
<%
/* 该域对象,只在本页面有效,出了页面就获取不到 */
pageContext.setAttribute("page", "pageContext");
%>
<%=pageContext.getAttribute("page") %>
<%-- 携带请求的参数(不要在这中间加注释!编译不出来!) --%>
<jsp:forward page="/2.jsp">
<jsp:param value="test" name="username"/>
<jsp:param value="123" name="password"/>
jsp:forward>
body>
html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>title>
head>
<body>
<%=pageContext.getAttribute("page") %>
<%-- <%=request.getAttribute("username") %> --%>
<%=request.getParameter("username") %>
<%=request.getParameter("password") %>
body>
html>el表达式
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
/* 一般系统方法中,需要一个 int 参数,一般会是常量 */
/* 只要有 pageContext 就可以向各个域中添加值,参数三表示对应域的常量 */
// pageContext.setAttribute("page", "pageContext", PageContext.PAGE_SCOPE);
// pageContext.setAttribute("page", "request", PageContext.REQUEST_SCOPE);
// pageContext.setAttribute("page", "session", PageContext.SESSION_SCOPE);
pageContext.setAttribute("page", "application", PageContext.APPLICATION_SCOPE);
%>
<%-- =pageContext.findAttribute("page") --%>
${page }
body>
html><%@page import="com.lanou3g.Address"%>
<%@page import="com.lanou3g.User"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
User user = new User();
user.setUsername("test");
user.setPassword("123");
request.setAttribute("u", user);
// 添加地址对象
Address address = new Address();
address.setCity("zh");
user.setAddress(address);
%>
${u.username }
${u.address.city }
${u["username"] }
${u['username'] }
body>
html><%@page import="java.util.HashMap"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
ArrayList arrayList = new ArrayList<>();
HashMap<String,ArrayList> hashMap = new HashMap<>();
arrayList.add(1);
arrayList.add(2);
arrayList.add(3);
request.setAttribute("list", arrayList);
hashMap.put("a", arrayList);
hashMap.put("b", arrayList);
hashMap.put("c", arrayList);
request.setAttribute("map", hashMap);
%>
${list }
${list[0] }
${map }
${map["a"] }
body>
html><%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title heretitle>
head>
<body>
<%
String str1 = null;
request.setAttribute("str1", str1);
String str2 = "";
request.setAttribute("str2", str2);
ArrayList<String> list1 = new ArrayList<>();
list1.add("aaa");
ArrayList<String> list2 = new ArrayList<>();
ArrayList<String> list3 = null;
ArrayList<String> list4 = new ArrayList<>();
list1.add("");
request.setAttribute("list1", list1);
request.setAttribute("list2", list2);
request.setAttribute("list3", list3);
request.setAttribute("list4", list4);
/* 测试三木运算符 */
String sex = "男";
request.setAttribute("sex", sex);
%>
${empty str1 }
${empty str2 }
${empty list1 }
${empty list2 }
${empty list3 }
${empty list4 }
${empty list3 ? "前面" : "后面" }
<br><input type="radio" value="男" name="sex" ${sex=="男" ? "checked='checked'" : "" }>男
radio" value="女" name="sex" ${sex=="女" ? "checked='checked'" : "" }>女