如何在jsp中检索init参数

小编典典

如何在jsp中检索init参数

jsp

我尝试使用jsp获取url数据，因为我将jsp代码用作

  String Url = pageContext.getServletConfig().getInitParameter("url").toString();
 out.println(Url);

web.xml

<servlet>
<servlet-name>IploginJSP</servlet-name>
<jsp-file>/Iplogin.jsp</jsp-file>
    <init-param>
    <param-name>url</param-name>
    <param-value>http://xxx.xxx.xxx.xxx:9000</param-value>
    </init-param>
</servlet>
<servlet-mapping>
<servlet-name>IploginJSP</servlet-name>
<url-pattern>/Iplogin</url-pattern>
</servlet-mapping>

但是我显示了NullPointerException

阅读 325

2020-06-08

共1个答案

小编典典

我认为这可以解决您的问题。

更改web.xml文件后，请重新启动服务器。

web.xml

<servlet>
    <servlet-name>GetInitParam</servlet-name>
    <jsp-file>/GetInitParam.jsp</jsp-file>
    <init-param>
        <param-name>url</param-name>  
        <param-value>hello</param-value>  
    </init-param>
</servlet>
<servlet-mapping>  
    <servlet-name>GetInitParam</servlet-name>  
    <url-pattern>/GetInitParam.jsp</url-pattern>  
</servlet-mapping>

GetInitParam.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>Example of getting init param</title>
</head>
<body>
<%!
    String url= null;
    public void jspInit() { 
        ServletConfig config = getServletConfig(); 
        url= config.getInitParameter("url");
    }
%>
<%
    System.out.println(url);
%>
</body>
</html>

更新1

如您在评论中所问to access parameters in all jsp files。在你所有的JSP文件访问参数你必须设置<context- param>你的web.xml

将以下几行 web.xml

<context-param>
<param-name>param1</param-name>
<param-value>hello</param-value>
</context-param>

您可以通过以下方式在jsp文件中访问此参数：

<% 
    String param1=application.getInitParameter("param1"); 
    System.out.println(param1);
%>

更新2

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

<context-param>
<param-name>param1</param-name>
<param-value>hello</param-value>
</context-param>
</web-app>

JSP文件

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Example of getting init param</title>
</head>
<body>
<%
    String param1=application.getInitParameter("param1"); 
    System.out.println(param1);
%>
</body>
</html>

2020-06-08