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JSP9个内置对象

2016-07-08 22:22 330 查看

JSP的第一个对象为out对象为向客户端输出信息

//out表示向客户端输出各种数据
//对输出缓冲区进行管理可以通过page属性来改变缓冲区
out.println("操");
out.print("cao");
out.newLine();
out.println("<br/>");
out.print("cao");

刷新缓冲区可以用
//强制刷新缓冲区的数据
out.flush();

清空缓存区也就是前面输出会清空掉
//清空缓冲区中的数据
out.clearBuffer();
out.clear();

out.println("获取当前的缓冲区大小:" + out.getBufferSize());
out.println("当前缓冲区剩余字节数目:" + out.getRemaining());

区别是clear和flush会冲突而clearBuffer不会与flush进行冲突
request对象用于封装客户端的请求

请求的方法名 <%= request.getMethod() %> <br/>
请求的url <%= request.getRequestURI() %>
获取请求的协议<%=request.getProtocol() %>
获取服务器的IP<%=request.getServerName() %>
请求的服务器端口<%=request.getServerPort() %>
客户端的IP地址<%= request.getRemoteAddr() %>
客户端的主机名<%= request.getRemoteHost() %>


首先创建一个提交的表单

<pre name="code" class="java"><form action = "do_register.jsp" method = "post">
用户名 <input type = "text" name = "userName"/></br>
技能
<input type = "checkbox" name = "skills" value = "java">java
<input type = "checkbox" name = "skills" value = "OC">OC
<input type = "checkbox" name = "skills" value = "Swift">Swift
</br>
<input type = "submit" value = "提交"/>
<input type = "reset" value = "重置"/>
</form>

随后在do_register.jsp中回去参数后，看是否成功随后配置property来进行设置

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<%
//getParameter方法获得用户名和技能数组
String userName = request.getParameter("userName");
String skills = "";
String skillArr[] = request.getParameterValues("skills");
for(int i = 0; i < skillArr.length; i++){
skills += skillArr[i];
}
//setAttribute方法
request.setAttribute("userName",userName);
request.setAttribute("skills",skills);
%>

<jsp:forward page="welcome.jsp"></jsp:forward>这里是处理注册是否成功，成功后跳转到welcome.jsp文件
用getParameter来获取

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>信息展示</title>
</head>
<body>
用户名<%= request.getParameter("userName")%>
技能<%=request.getParameter("skills")%>

</body>
</html>这里要区分一下 getParameter来处理客户端的请求而setAttribute来表示webPages之间的传值

response方法，用于返回客户端的请求

<%
//设置头部的信息设置网页数据不缓存
response.setHeader("cache-Control","no-cache");
//设置每两秒刷新一次
response.setIntHeader("Refresh",2);
out.println("date is " + new java.util.Date().toString());
%>

设置页面的直接跳转
//实现页面的跳转
response.sendRedirect("http://www.baidu.com");session对象用于设置会话在浏览器向服务器请求时，有唯一的一个sessionID 服务器会进行判定相同的才给予响应
<%@page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>Session</title>
</head>
<body>

session 的唯一标示符 32位长字符<%=session.getId() %>
session的创建时间<%= new java.util.Date( session.getCreationTime()).toString() %>
session的最后访问时间<%=session.getLastAccessedTime() %>
session的失效时间 <%=session.getMaxInactiveInterval()%>

</body>
</html>

实现一个登陆验证首先在Login创建一个表单

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body>
<form acton = "do_login.jsp" method = "post">
userName:<input type = "text" name = "userName"/>
password:<input type = "password" name = "password"/>
<input type = "submit" value = "submit">
<input type = "reset" value = "reset">
</form>
</body>
</html>随后在验证表单do_login.jsp中进行登陆的验证
session中配置属性

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>

<%
String userName = request.getParameter("userName");
String password = request.getParameter("password");
//验证是否登录成功
if(userName != null && password != null){
//会话中配置java对象
session.setAttribute("userName",userName);
//随后刷新跳转到欢迎界面
response.setHeader("refresh","2;URL=welcome.jsp");
}
%>随后在欢迎界面根据session获得的不同值来输出不同的值
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>欢迎界面</title>
</head>
<body>
<% if(session.getAttribute("userName") != null) { %>
欢迎 <%=session.getAttribute("userName") %>
<a href = "logout.jsp">注销</a>
</br>
<%else { %>
请先登录
<a href = "login.jsp">登录</a>
<%} %>
<%if(session.isNew()) {%>
<br/>
欢迎新用户
<%}else{ %>
欢迎老用户
<%} %>
</y>
</html>

随后在退出登陆的界面来进行退出
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%
//退出的代码
session.invalidate();
response.setHeader("refresh","2;URL=welcome.jsp");
%>

config属性主要在severlt中进行配置可以在WEB-INF目录下的web.xml文件中进行配置

application属性用于设置全局的变量

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>application</title>
</head>
<body>

服务器信息<%=application.getServerInfo() %></br>
应用名称<%=application.getServletContextName()%><br/>
主机名称<%=application.getVirtualServerName() %></br>
</body>
</html>可以做一个简单的计数器如果页面是第一次访问的话就输出值，随后保存到application中，如果是第二次开始访问的，那么就从application中取出值，随后进行++和存值得操作
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>页面访问计数器</title>
</head>
<body>
<%
Object obj = application.getAttribute("counter");
//判断是否为空空为第一次
if(obj == null){
application.setAttribute("counter",new Integer(1));
out.println("该页面被访问了1次<br/>");
}else{
int counterValue = Integer.parseInt(obj.toString());
counterValue++;
out.println("该页面被访问了" + counterValue + "次<br/>");
application.setAttribute("counter",counterValue);
}
%>
</body>
</html>page属性相当于java中的this指针，用于指向本页面，其是继承自object类的
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body>
page对象的字符串<%=page.toString() %>
当前的object类<%=page.getClass() %>
当前的hashCode值<%=page.hashCode() %>
继承自object类
</body>
</html>异常类必须配置error_page属性
在throw_error.jsp中人为的指定一个错误，随后进行抛出，指定错误界面为handle_error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page errorPage="handle_error.jsp" %>
<!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>抛出异常类</title>
</head>
<body>
<%
int a = 10;
int b = a / 0;
%>
</body>
</html>随后在handle_error.jsp中指定isErrorPage = true 随后输出一些异常的信息即可
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page isErrorPage="true" %>
<!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>异常处理</title>
</head>
<body>
异常描述信息
<%
out.println(exception.getMessage());
%>
exception对象的字符串描述
<%=exception.toString() %>
异常堆栈信息
<%=exception.printStackTrace() %>
</body>
</html>page_Context可以说是一个集大成者，他可以转换为out 但是系统默认已经带有一个out了，所以自己命名的话只能命名为其他名称
<%
JspWriter myOut = pageContext.getOut();
myOut.println("hello world");也可以在session 中设置值，随后进行取值和输出
pageContext.setAttribute("dakim","cao",pageContext.SESSION_SCOPE);
String value = session.getAttribute("dakim").toString();
out.println(value);

好的博客可以参考 http://blog.csdn.net/yenange/article/details/5949518

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