JAVA遇见HTML——JSP篇（学习笔记）

发表于： 2019年10月24日 2019年11月3日
分类： Java

学习资源路径 https://www.imooc.com/learn/166

结构如下

通过http://localhost:8080/myhome/index.jsp即可访问myhome下的index.jsp文件。

<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
	this is the first page
	<!-- html注释 客户端可见 -->
	<%-- html注释 客户端不可见 --%>
	<%
		out.println("哈哈"); // 脚本中注释，不可见
	%>
	<%!String abc = "哈哈";%>
	<%=abc%>
</body>
</html>

out对象

request对象

中文参数乱码问题
①设置请求编码

request.setCharacterEncoding(“UTF-8”)的作用是设置对客户端请求和数据库取值时的编码，不指定的话使用iso-8859-1。(只解决POST乱码)

②server.xml设置默认编码

response对象

session对象

<%@ page language="java" import="java.util.*,java.text.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
    <!-- session创建时间戳 -->
	<%= session.getCreationTime() %>
<br/>
	<% 
	SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
	// session创建时间
	out.println(simpleDateFormat.format(new Date(session.getCreationTime())));
	// session_id
	out.println("sessionId:"+session.getId());
	// 设置session_id关联的属性值
	session.setAttribute("username", "Mr.Wang");
	// 获取session_id关联的属性值
	out.println(session.getAttribute("username"));
	session.setAttribute("age", 11);
	// 获取session_id关联的属性名
	String[] values = session.getValueNames();
	for(int i = 0;i<values.length;i++){
		out.println();
		out.println(values[i]+':'+session.getAttribute(values[i]));
	}
	// 获得session的最大存活时间,默认是1800秒
	out.println(session.getMaxInactiveInterval());
	// 设置session的最大存活时间
	session.setMaxInactiveInterval(1000);
	out.println(session.getMaxInactiveInterval());
	// 销毁会话
	session.invalidate();
	%>
</body>
</html>

设置session超时时间

application对象

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
	<% 
	  application.setAttribute("city", "JiNing");
	  application.setAttribute("area", "WeiShan"); 
	%>
	城市：<%=application.getAttribute("city")%><br/>
	县区：<%=application.getAttribute("area")%><br/>
 
	servlet引擎以及版本号：<%=application.getServerInfo()%><br/>
	所有属性名：
	<%
	  Enumeration attribute = application.getAttributeNames();
	  while(attribute.hasMoreElements()){
		  out.println(attribute.nextElement());
	  }
	%>
</body>
</html>

输出如下：
城市：JiNing
县区：WeiShan
servlet引擎以及版本号：Apache Tomcat/8.5.46
所有属性名： javax.servlet.context.tempdir area org.apache.catalina.resources city org.apache.tomcat.InstanceManager org.apache.catalina.jsp_classpath javax.websocket.server.ServerContainer org.apache.jasper.compiler.ELInterpreter org.apache.jasper.compiler.TldCache org.apache.tomcat.JarScanner org.apache.jasper.runtime.JspApplicationContextImpl
page对象

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
  Object类：<%= page.getClass() %><br/>
  Object类的hash码：<%= page.hashCode() %><br/>
  Object类转换成String对象：<%= page.toString() %>
</body>
</html>

输出如下：
Object类：class org.apache.jsp.page_jsp
Object类的hash码：351642781
Object类转换成String对象：org.apache.jsp.page_jsp@14f5a49d
pageContext对象

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
  获取session对象并使用：<%= pageContext.getSession().getAttribute("username") %>
  <% 
	  pageContext.forward("index.jsp");  // 跳转页面
  %>
</body>
</html>

config对象

exception对象

自定义一个异常错误处理页面

<%@ page language="java" contentType="text/html; charset=utf-8" isErrorPage="true"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<%= exception.getMessage() %><br/>
<%= exception.toString() %>
</body>
</html>

当发生异常时，指定异常处理页面

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" errorPage="exception.jsp"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<%
  out.println(100/0);
%>
</body>
</html>

JavaResource目录下点击创建包package，点击包创建一个class类，目录结构如下：

①Eclipse使用普通方式创建JavaBean

package com;
public class User {
	private String username;
	private int age;
 
	public User() {
		// TODO Auto-generated constructor stub
	}
	@Override
	public String toString() {
		return "User [username=" + username + ", age=" + age + ", toString()=" + super.toString() + "]";
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
}

备注：可以使用ALT+/创建成员方法和变量，Alt+Shift+S快速生成getter和setter

引用javaBean

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<%@ page import="com.User" %>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<%
  User user = new User();
  user.setUsername("丫丫");
  user.setAge(36);
%>
用户名：<%=user.getUsername() %><br/>
年龄：<%=user.getAge() %>
</body>
</html>

②使用jsp:useBean方式

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<jsp:useBean id="user" class="com.User" scope="page"></jsp:useBean>
<%
	user.setUsername("丫丫");
	user.setAge(36);
%>
用户名：<%=user.getUsername() %><br/>
年龄：<%=user.getAge() %>
</body>
</html>

jsp:setProperty的四种使用方式

表单页面

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<form method="post" action="do_login.jsp">
用户名：<input type="text" name="username"/>
年龄：<input type="text" name="age"/>
<button>提交</button>
</form>
</body>
</html>

提交页面

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<% request.setCharacterEncoding("utf-8"); %>
<jsp:useBean id="user" class="com.User" scope="page"></jsp:useBean>
<!-- ①匹配所有属性 -->
 <jsp:setProperty property="*" name="user"/> 
<!-- ②使用request对象中的一个参数值来指定Bean中的一个属性值 -->
 <jsp:setProperty property="username" name="user"/> 
<!-- ③和表单无关 手工赋值 -->
  <jsp:setProperty property="username" name="user" value="佟丽娅"/>  
<!-- ④和request参数关联 -->
  <jsp:setProperty property="username" name="user" param="username"/>  
用户名：<%= user.getUsername() %><br/>
年龄：<%= user.getAge() %>
</body>
</html>

jsp:getProperty使用

—表单同上—

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<% request.setCharacterEncoding("utf-8"); %>
<jsp:useBean id="user" class="com.User" scope="page"></jsp:useBean>
<jsp:setProperty property="*" name="user"/>
用户名：<jsp:getProperty property="username" name="user"/>
年龄：<jsp:getProperty property="age" name="user"/>
</body>
</html>

javaBean的四个作用域范围

<%@ page language="java"  import="java.util.*" contentType="text/html; charset=utf-8"%>
<%@ page import="com.User" %>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<jsp:useBean id="user" class="com.User" scope="application"></jsp:useBean>
<!-- 使用jsp:getProperty获取 -->
用户名：<jsp:getProperty property="username" name="user"/>
年龄：<jsp:getProperty property="age" name="user"/>
<hr/>
<!-- 使用内置对象获取 -->
用户名：<%= ((User)application.getAttribute("user")).getUsername() %>
年龄：<%= ((User)application.getAttribute("user")).getAge() %>
</body>
</html>

创建一个登陆处理JavaBean

package com;
 
public class LoginDao {
	public static boolean doLogin(User u) {
		if ("admin".equals(u.getUserName()) && "123456".equals(u.getPassword())) {
			return true;
		} else {
			return false;
		}
	}
}

jsp中调用javabean重写登陆逻辑

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<jsp:useBean id="userBean" class="com.User" scope="page"></jsp:useBean>
<jsp:useBean id="LoginDao" class="com.LoginDao" scope="page"></jsp:useBean>
<!DOCTYPE html>
<html>
<head>
<title>登录处理页面</title>
</head>
<body>
<% request.setCharacterEncoding("utf-8"); %>
<jsp:setProperty property="*" name="userBean"/>
<%
 if(LoginDao.doLogin(userBean)){
	 out.println("登录成功");
 }else{
	 out.println("登录失败");
 }
%>
</body>
</html>

http状态管理之cookie

登陆表单 login.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
    <%
      Cookie[] cookies = request.getCookies();
      String userName = "";
      String password = "";
      if(cookies!=null && cookies.length>0){
    	  for(Cookie c:cookies){
    		  if("username".equals(c.getName())){
    			  userName = c.getValue();
    		  }
    		  if("password".equals(c.getName())){
    			  password = c.getValue();
    		  }
    	  }
      }
    %>
	<form method="post" action="do_login.jsp">
		用户：<input type="text" name="username" value="<%= userName %>"/> 
		密码：<input type="text" name="password" value="<%= password%>"/> 
		十天免登录：<input type="checkbox" name="is_remember" />
		<button>登录</button>
	</form>
</body>
</html>

do_login.jsp

<%@ page language="java" import="java.util.*"
	contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
	<%
        request.setCharacterEncoding("utf-8");
		String[] isCheckBox = request.getParameterValues("is_remember");
		if (isCheckBox != null && isCheckBox.length > 0) {
			Cookie userName = new Cookie("username",request.getParameter("username"));
			Cookie password = new Cookie("password",request.getParameter("password"));
			userName.setMaxAge(864000);
			password.setMaxAge(864000);
			response.addCookie(userName);
			response.addCookie(password);
		}else{
			Cookie[] cookies = request.getCookies();
			for(Cookie c:cookies){
				c.setMaxAge(0);
			}
		}
	%>
	<a href="user_info.jsp">查看用户信息</a>
</body>
</html>

user_info.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<%
  String userName = "";
  String password = "";
  Cookie[] cookies = request.getCookies();
  for( Cookie c:cookies){
	  if("username".equals(c.getName())){
		  userName =c.getValue();
	  }
	  if("password".equals(c.getName())){
		  password = c.getValue();
	  }
  }
%>
用户名：<%=userName %>
密码：<%=password %>
</body>
</html>

include指令

file.jsp

<%@page import="java.text.SimpleDateFormat"%>
<%@page import="java.text.DateFormat"%>
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<%
  Date d = new Date();
  DateFormat df = new SimpleDateFormat("yyyy年MM月dd日");
  String date = df.format(d);
%>
<%=date %>
</body>
</html>

include.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<%@include file="file.jsp" %>
</body>
</html>

<jsp:include page="file.jsp" flush="false"></jsp:include>

动作在请求期间被执行，而include指令在编译期页面间被执行

<%@ page language="java" contentType="text/html; charset=utf-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
  <jsp:forward page="user.jsp">
    <jsp:param value="admin@qq.com" name="email"/>
  </jsp:forward>
</body>
</html>

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最难走的路，往往是上坡路。

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