表單
<form action = "" method = "">
action
action:目標地址，把請求交給誰處理；action可以不設置，也可以是空字符串(提交給自己處理)
method
method: get | post，默認是get
get和post的區別
- get:參數比較小用get，要取服務器數據
- post:向服務器提交數據
- get會把參數顯示在地址欄，post不會
- 中文參數儘量不要使用get方式
- 兩種請求的請求體大小，get是有限制的
輸入手段
文本框，密碼框，文本區域，下拉列表，但選框，複選框，隱藏框......,提交按鈕，重置按鈕 要求：往服務器傳值的地方必須指定name屬性，作爲參數名傳到服務器
<input type="text" name="code" class="....">
basePath
在jsp代碼的上方能看到一個String變量basePath，被賦值爲
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
對於我的web項目來說，basePath其實就等於http://localhost:8088/jsp/，所以當你想要訪問其他網頁，寫路徑的時候，可以直接利用basePath
提交信息給input_action.jsp頁面
提交信息，分三步：
- 設置form的action屬性爲被提交的網站名稱
- 填寫輸入部分的name，後面獲取信息也要通過name
- 被提交網頁通過request.getPramamter(String arg0)方法獲取信息
<!-- 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%>"><!-- 指定當前頁面相對路徑得根目錄在哪，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">學號：</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>這裏我設置了action提交的時候傳給input_action.jsp這個網頁，傳輸方式爲post，兩個輸入框分別命名爲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>
<%
// 設置編碼格式，避免中文亂碼
request.setCharacterEncoding("UTF-8");
// 獲取請求參數，參數名爲id，對應學號
String id = request.getParameter("id");
// 獲取請求參數，參數名爲name，對應姓名
String name = request.getParameter("name");
%>
<ul>
<li>學號：<%= id %></li>
<li>姓名：<%= name %></li>
</ul>
</body>
</html>爲了避免輸入框輸入中文，導致傳到input_action.jsp網頁的信息是亂碼，這裏要利用request.setCharacterEncoding("UTF-8")方法將其設置爲中文編碼格式。然後利用request.getParameter(String arg0)方法接受請求的參數，最後打印出來
中文亂碼問題解決辦法
- 將請求參數以ISO-8859-1編碼形式轉換成字節數組，再將字節數組轉換成字符串
- request.setCharacterEncoding(“UTF-8”);
訪問web手段
- 地址欄
http://localhost:8088/jsp/c02/input_action.jsp?name=x&code=1234
只要在URL後面跟上一個"?"，然後繼續跟上pname1=pvalue1&pname2=pvalue2&即可
- 超鏈接
<a href="<%= basePath %>c02/input_action.jsp?code=00000&name=張三">張三訪問</a>
題目：提交三條邊，輸出面積
<%@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三條邊不能構成三角形，請重新輸入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
} else {
double p = (bian_a + bian_b + bian_c) / 2.0;
out.println("邊長爲" + bian_a + "," + bian_b + "," + bian_c + "的面積爲：" + Math.sqrt(p * Math.abs(bian_a - p) * Math.abs(bian_b - p) * Math.abs(bian_c - p)));
}
} else {
out.println("邊不能含有非數字信息，請重新輸入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
}
} else {
out.println("缺少邊的信息，請重新輸入");
%>
<a href = "<%= basePath %>c02/triangle.jsp">返回</a>
<%
}
%>
</body>
</html>input.jsp就不附上了，原來的代碼改一下name，在新增一個輸入框就行了