JSP中获取参数的3中方法

╰+哭是因爲堅強的太久メ 2022-07-15 04:56 515阅读 0赞

我们有时需要在jsp页面中获取request中的参数，然后根据这些参数决定页面的一些内容或者动作。通常我们通过equest.getParameter(xxx);来获取，除了这种方式外，我们还可以通过param或者js来实现。

**通过EL中的param**  
EL中有很多内置对象，我们使用param就可以获取参数  
JSP EL Implicit Objects:  
The JSP expression language supports the following implicit objects:

Implicit object Description  
pageScope Scoped variables from page scope  
requestScope Scoped variables from request scope  
sessionScope Scoped variables from session scope  
applicationScope Scoped variables from application scope  
**param Request parameters as strings**  
paramValues Request parameters as collections of strings  
header HTTP request headers as strings  
headerValues HTTP request headers as collections of strings  
initParam Context-initialization parameters  
cookie Cookie values  
pageContext The JSP PageContext object for the current page

<c:if test="${not empty param.xxxx}">
         //do something
    </c:if>

或者你在js中这样

通过纯js来获取

我们看看实际演示效果  
源代码，我在tomcat7上运行，最基本的配置就不写了，你需要提供jstl的那些jar包。

<%@page pageEncoding="UTF-8" %>
    
    <%@ page import="java.util.*" %>
    
    <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <%@taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
    <%@taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
    
    <%@ page language="java" contentType="text/html; charset=UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <% String appName = request.getParameter("name"); pageContext.setAttribute("appName", appName); %>
    
        <title>演示如何获取参数</title>
    <script type="text/javascript"> function getQueryParameter ( parameterName ) { var queryString = window.top.location.search.substring(1); var parameterName = parameterName + "="; if ( queryString.length > 0 ) { begin = queryString.indexOf ( parameterName ); if ( begin != -1 ) { begin += parameterName.length; end = queryString.indexOf ( "&" , begin ); if ( end == -1 ) { end = queryString.length } alert(unescape ( queryString.substring ( begin, end ) )); return; } } alert("null"); } </script>
    </head>
    <body>
        <c:if test="${not empty param.name}">
           Name is <c:out value="${param.name}" />
        </c:if>
        </br>
        <c:if test="${not empty param.name}">
           Name is <%=appName%>
        </c:if>
        </br>
        <input id="username" type="text" name="users" value="name" onclick="getQueryParameter('name')">
    </body>
    </html>

运行效果  
![这里写图片描述][20161102175956754]

[20161102175956754]: /images/20220715/27e9e03fafb14eff8610a1b6e0421a20.png