📄 84.html

📁 写给JSP初级程序员的书
💻 HTML
字号:
<html>

<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">

<meta name="description" content="Java,JDBC,EJB,Open Source,jdk,rmi">
<meta name="Keywords"
content="Java, servlets, Java servlet, Javascript, ActiveX, VRML,
        applet, applets, directory, news, jdbc, applications, 
        Java applications, Java developer, Java development, developer, 
        classes, Jars.com, Jars, intranet, Java applet, Javabeans, 
        Java products, JDK, Java development kit, java development environment, JIT,
        JavaPlan, enterprise tools, JVM, Java Virtual Machine, Java resources, 
        SUN, CGI, Perl, database, network, html,
        xml, dhtml, rating, ratings, review, jars, cgi, programming,
        software review, software rating">
<title>csdn_如何设置application 变量</title>
<style>
.news {   BACKGROUND: #007cd3;  font-family: "宋体"; font-size: 9pt }
.t {  font-family: "宋体"; font-size: 9pt }
.t1 { color:#007cd3;  font-family: "宋体"; font-size: 9pt }
.white { font-family: "宋体"; font-size: 9pt;color:#FFFFFF }
.red { font-family: "宋体"; font-size: 9pt;color:#FF0000 }
A:visited {color:#0000FF}
A:hover {color: #ff6666; text-decoration: none}
.text {font-size: 12px; line-height: 160%; font-family: "宋体"}
.text1 {color:#000000; font-size: 12px; line-height: 130%; font-family: "宋体"; text-decoration: none}
.text1:visited {color:#000000}
.text1:hover {color: #000000}
.text2 {color:#000000; font-size: 12px; line-height: 130%; font-family: "宋体"; text-decoration: none}
.text2:visited {color:#000000}
.text2:hover {color: #000000}
.text3 {font-size: 12px; line-height: 100%; font-family: "宋体"; text-decoration: none}
.large {font-size: 14.8px; line-height: 130%}
</style>

</head>

<body


<center>




  <tr>
    <td WIDTH="100%" VALIGN="TOP">
      <tr>
        <td WIDTH="100%" CLASS="white"></td>
      </tr>
    
      <tr>
        <td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>如何设置application 变量</td>
        <p></p>
</td>
      </tr>
      <tr>        <td WIDTH="100%" bordercolor="#FFFFFF" CLASS="t" bgcolor="#F0F0F0" colspan="2">
       <BR>
application变量是对一个web application有效的全局变量，在保存一些全局有效的值时非常有用。与session变量不同，application变量可以用application.getAttribute()和application.setAttribute()来访问。<BR>
<BR>
在JSP中，可以自动引用application变量，指代当前的web 应用。（有关web 应用，我将在另外的地方讨论。）<BR>
<BR>
在引用application 变量时，必须使用同步。并且，需要测试一个application属性是否已经存在。请仔细研究下面的代码，在下面，设置了一个叫“change&quot;的application 属性，保存一个整型值。关于在servlet中使用application变量，方法与下面的代码一致，不过，需要先说明一个application如下:<BR>
<BR>
servletContext application=getServletContext();<BR>
<BR>
后面的一段函数是env.java的片断，可以看看在servlet中如何使用application变量的。<BR>
<BR>
Integer count = null;<BR>
<BR>
synchronized (application) {<BR>
<BR>
  count = (Integer) application.getAttribute(&quot;change&quot;);<BR>
<BR>
  if (count == null)<BR>
<BR>
    count = new Integer(0);<BR>
<BR>
  count = new Integer(count.intValue() + 1);<BR>
<BR>
  application.setAttribute(&quot;change&quot;, count);<BR>
<BR>
}<BR>
<BR>
<BR>
<BR>
private void printApplication(PrintWriter pw, HttpServletRequest req)<BR>
<BR>
    throws IOException<BR>
<BR>
  {<BR>
<BR>
   ServletContext application = getServletContext();<BR>
<BR>
<BR>
<BR>
pw.println(&quot;&lt;h1&gt;Application Information:&lt;/h1&gt;&quot;);<BR>
<BR>
    pw.println(&quot;&lt;table&gt;&quot;);<BR>
<BR>
    pw.print(&quot;&lt;tr&gt;&lt;td&gt;Major Version&lt;td&gt;&quot;);<BR>
<BR>
    pw.println(application.getMajorVersion());<BR>
<BR>
  pw.print(&quot;&lt;tr&gt;&lt;td&gt;Minor Version&lt;td&gt;&quot;);<BR>
<BR>
  pw.println(application.getMinorVersion());<BR>
<BR>
pw.print(&quot;&lt;tr&gt;&lt;td&gt;Server Info&lt;td&gt;&quot;);<BR>
<BR>
    pw.println(application.getServerInfo());<BR>
<BR>
    pw.print(&quot;&lt;tr&gt;&lt;td&gt;Real Path (of pathinfo)&lt;td&gt;&quot;);<BR>
<BR>
    pw.println(application.getRealPath(req.getPathInfo()));<BR>
<BR>
    pw.print(&quot;&lt;tr&gt;&lt;td&gt;Mime-type (of pathinfo)&lt;td&gt;&quot;);<BR>
<BR>
    pw.println(application.getMimeType(req.getPathInfo()));<BR>
<BR>
    pw.println(&quot;&lt;/table&gt;&quot;);<BR>
<BR>
<BR>
<BR>
    pw.println(&quot;&lt;h1&gt;Application Variables:&lt;/h1&gt;&quot;);<BR>
<BR>
    pw.println(&quot;&lt;table&gt;&quot;);<BR>
<BR>
<BR>
<BR>
  Enumeration e = application.getAttributeNames();<BR>
<BR>
while (e.hasMoreElements()) {<BR>
<BR>
      String name = (String) e.nextElement();<BR>
<BR>
    pw.print(&quot;&lt;tr&gt;&lt;td&gt;&quot;);<BR>
<BR>
      pw.print(name);<BR>
<BR>
      pw.print(&quot;&lt;td&gt;&quot;);<BR>
<BR>
      pw.println(application.getAttribute(name));<BR>
<BR>
    }<BR>
<BR>
<BR>
<BR>
    pw.println(&quot;&lt;/table&gt;&quot;);<BR>
<BR>
}<BR>
<BR>
<BR>
<BR>
%&gt;<BR>
<BR>
<BR>
<BR>
&lt;html&gt;<BR>
<BR>
&lt;head&gt;&lt;title&gt;Counter&lt;/title&gt;&lt;/head&gt;<BR>
<BR>
&lt;body bgcolor=#ffffff&gt;<BR>
<BR>
<BR>
<BR>
&lt;h1&gt;Welcome, visitor: &lt;%= count %&gt;&lt;/h1&gt;<BR>
<BR>
<BR>
<BR>
&lt;/body&gt;<BR>
<BR>
&lt;/html&gt;<BR>
<BR>
<BR>
<BR>
        </td>
      </tr>
    </td>
  </tr>
</div>
</body>
</html>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -