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[JSP]JSP内置对象（1）

2015-05-13 16:32 260 查看
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：



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>




填写完成后提交：

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