表单
<form action = "" method = "">action
action:目标地址，把请求交给谁处理；action可以不设置，也可以是空字符串(提交给自己处理)
method
method: get | post，默认是get
get和post的区别
- get:参数比较小用get，要取服务器数据
- post:向服务器提交数据
- get会把参数显示在地址栏，post不会
- 中文参数尽量不要使用get方式
- 两种请求的请求体大小，get是有限制的
输入手段
文本框，密码框，文本区域，下拉列表，但选框，复选框，隐藏框......,提交按钮，重置按钮
要求：往服务器传值的地方必须指定name属性，作为参数名传到服务器
<input type="text" name="code" class="....">basePath
在jsp代码的上方能看到一个String变量basePath，被赋值为
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";对于我的web项目来说，basePath其实就等于http://localhost:8088/jsp/，所以当你想要访问其他网页，写路径的时候，可以直接利用basePath
提交信息给input_action.jsp页面
提交信息，分三步：
- 设置form的action属性为被提交的网站名称
- 填写输入部分的name，后面获取信息也要通过name
- 被提交网页通过request.getPramamter(String arg0)方法获取信息
<!-- input.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%>"><!-- 指定当前页面相对路径得根目录在哪，目前的basePath = "http://localhost:8088/jsp/" -->
<title>My JSP 'input.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">
<jsp:include page = "../res.jsp"/>
</head>
<body class = "container">
<div>
<h3 class = "page-header">request.getPramamter()的用法</h3>
<form action = "<%=basePath%>c02/input_action.jsp" method = "post" class = "form-horizontal">
<div class = "form-group">
<label class = "col-md-3 control-label">学号：</label>
<div class = "col-md-5">
<input type = "text" name = "id" class = "form-control"><!-- 指定name -->
</div>
</div>
<div class = "form-group">
<label class = "col-md-3 control-label">姓名：</label>
<div class = "col-md-5">
<input type = "text" name = "name" class = "form-control"><!-- 指定name -->
</div>
</div>
<div class = "form-group">
<div class = "col-md-offset-3 col-md-5">
<button type = "submit" class = "btn btn-primary">提交</button>
</div>
</div>
</form>
</div>
</body>
</html>这里我设置了action提交的时候传给input_action.jsp这个网页，传输方式为post，两个输入框分别命名为id和name
<!-- input_action.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 'input_action.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">
</head>
<body>
<%
// 设置编码格式，避免中文乱码
request.setCharacterEncoding("UTF-8");
// 获取请求参数，参数名为id，对应学号
String id = request.getParameter("id");
// 获取请求参数，参数名为name，对应姓名
String name = request.getParameter("name");
%>
<ul>
<li>学号：<%= id %></li>
<li>姓名：<%= name %></li>
</ul>
</body>
</html>为了避免输入框输入中文，导致传到input_action.jsp网页的信息是乱码，这里要利用request.setCharacterEncoding("UTF-8")方法将其设置为中文编码格式。然后利用request.getParameter(String arg0)方法接受请求的参数，最后打印出来
中文乱码问题解决办法
- 将请求参数以ISO-8859-1编码形式转换成字节数组，再将字节数组转换成字符串
- request.setCharacterEncoding(“UTF-8”);
访问web手段
1.地址栏
http://localhost:8088/jsp/c02/input_action.jsp?name=x&code=1234只要在URL后面跟上一个"?"，然后继续跟上pname1=pvalue1&pname2=pvalue2&即可
2.超链接
<a href="<%= basePath %>c02/input_action.jsp?code=00000&name=张三">张三访问</a>题目：提交三条边，输出面积
<%@page import="java.util.regex.Pattern"%>
<%@ 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 'input_action.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">
</head>
<body>
<%
String a = request.getParameter("a");
String b = request.getParameter("b");
String c = request.getParameter("c");
if(a != "" && b != "" && c != "") {
Pattern pattern = Pattern.compile("[1-9]");
if(pattern.matcher(a).matches() && pattern.matcher(b).matches() && pattern.matcher(c).matches()) {
double bian_a = Double.parseDouble(a);
double bian_b = Double.parseDouble(b);
double bian_c = Double.parseDouble(c);
if(bian_a + bian_b <= bian_c || bian_a + bian_c <= bian_b || bian_b + bian_c <= bian_a) {
out.println("Sorry三条边不能构成三角形，请重新输入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
} else {
double p = (bian_a + bian_b + bian_c) / 2.0;
out.println("边长为" + bian_a + "," + bian_b + "," + bian_c + "的面积为：" + Math.sqrt(p * Math.abs(bian_a - p) * Math.abs(bian_b - p) * Math.abs(bian_c - p)));
}
} else {
out.println("边不能含有非数字信息，请重新输入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
}
} else {
out.println("缺少边的信息，请重新输入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
}
%>
</body>
</html>input.jsp就不附上了，原来的代码改一下name，在新增一个输入框就行了
