[JSP]JSP内置对象（1）

来源：互联网发布：无间道3电影解析知乎编辑：程序博客网时间：2024/04/30 13:17

所谓内置对象指在JSP页面中已经默认内置的Java对象。它们在JSP页面初始化时生成，由容器实现和管理。这些对象可以直接在JSP页面使用。经常使用的JSP内置对象有out、request、response、session、application、config、pageContext和exception。
下面简单介绍下JSP的各类内置对象：

1、Out 对象

out对象用来向客户端输出数据，被封装为javax.servlet.jsp.JspWriter类对象，通过JSP容器变换为java.io.PrintWriter类对象。Servlet使用java.io.PrintWriter类对象向网页输出数据。
eg:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><html>  <body>    <%    out.print("<font size=4 color=blue>");    out.print("JavaScript内置对象");    out.print("</font>");     %>  </body></html>

2、Request 对象

HTTP协议是客户与服务器之间提交请求信息（request）与响应信息（response）的通信协议。request对象是从客户端向服务器发出请求，代表客户端请求信息，主要用于接收客户端通过HTTP协议传送给服务器的数据。该对象继承于ServletRequest接口，被包装成HttpServletRequest接口。

方法名称说明 String getParameter(String name) 用来获取用户提交的数据 String[] getParameterValues(String name) 返回指定参数的所有值 setCharacterEncoding(String charset) 设置响应使用字符编码格式 void setAttribute(String name,java.lang.Objectvalue）转发请求时并传数据到转发页面 Object getAttribute(String name) 请求转发后的页面使用该方法获取属性值 removeAttribute(String name) 把设置在request范围内的属性删除 getRemoteAddr() 获得客户端IP地址 Cookie[]getCookies() 返回客户端Cookie对象，结果是一个Cookie数组

eg:

/*request.html*/<!DOCTYPE html><html>  <head>    <title>requestb.html</title>    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="this is my page">    <meta http-equiv="content-type" content="text/html; charset=UTF-8">    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->  </head>  <body>    <form action="get.jsp" method="post" name="form1">    Pleasr Enter your school name:    <Input type="text" name="schoolname">    <Input type="submit" name="submit" value= "xxx" >    </form>  </body></html>

/*get.jsp*/<%@ 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>My JSP 'get.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body bgcolor="white">   <p>获取文本框提交的信息：   <%String textContent=new String(request.getParameter("schoolname")); %>   <%=textContent %>  </body></html>

输入学校名字：

提交后：
这里写图片描述
再列一个全面一点的例子：
用于获取用户填写的表单

/*example.jsp*/<%@ 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><script language="javascript">function checkEmpty(form){    for (i=0;i<form.lengh;i++)    {        if(form.elements[i].value=="")        {            alert("表单信息不能为空");            return false;        }    }}</script>  <head>    <base href="<%=basePath%>">    <title>My JSP 'example.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>    <form name="form1" method="post" action="a.jsp" onSubmit="return checkEmpty(form1)">        <table border="0">            <tr>                <td>输入姓名：</td>                <td><input type="text" name="textOne"></td>            </tr>            <tr>                <td>选择性别：</td>                <td><INPUT type="radio" name="sex" value="男" checked="default">男</td>                <td><INPUT type="radio" name="sex" value="女">女</td>            </tr>            <tr>                <td>选择您喜欢的专业：</td>                <td><input type="checkbox" name="item" value="NIIT">NIIT</td>                <td><input type="checkbox" name="item" value="对日软件">对日软件</td>                <td><input type="checkbox" name="item" value="中加合作">中加合作</td>            </tr>            <tr>                <td>隐藏域的值为：</td>                <td><input type="hidden" name="major" value="对日软件">对日软件</td>        </table>        <input type="submit" name="Submit" value="提交">        <INPUT TYPE="reset" value="重置">    </form>  </body></html>

/*a.jsp*/<%@ 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>  <%request.setCharacterEncoding("UTF-8");%>  <head>    <base href="<%=basePath%>">    <title>My JSP 'a.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>  <div align="center">    <table border="0">        <tr>            <td>您的姓名:</td>            <td><%=request.getParameter("textOne") %></td>        </tr>        <tr>            <td>您的性别:</td>            <td><%=request.getParameter("sex") %></td>        </tr>        <tr>            <td>您喜欢的专业：</td>            <%String itemName[]=request.getParameterValues("item");            if(itemName==null)            {                out.print("<td>"+"都不喜欢"+"</td>");                out.print("</tr>");            }            else            {                for(int k=0;k<itemName.length;k++)                {                    out.print("<td>"+itemName[k]+"</td>");                }                out.print("<tr>");            }%>        <tr>            <td>获取隐藏域的值为：</td>            <td><%=request.getParameter("major") %></td>        </tr>    </table>    <a href="example.jsp">返回</a>  </div>  </body></html>

这里写图片描述
填写完成后提交：

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