JSP由浅入深(3)―― 通过表达式增加动态内容_MySQL
在我们前面的章节中，任何的HTML文件都可以转变成JSP文件，做法是通过改变它的扩展名为.jsp。当然，我们要知道是什么使得JSP有用呢？答案是嵌入Java的能力。将下列文本放置在一个以.jsp为扩展名的文件中，比如说这个文件为myjsp.jsp，然后将这个文件放置到你的JSP目录下并且在浏览器上看它。以下是具体的代码：
Hello! The time is now
这里要注意，每次你在浏览器中重载网页的时候，它就出现当前时间。字符系列的作用是圈起Java表达式，这个表达式将在运行的时候被计算。
正因为这样，使用JSP产生动态HTML网页来响应用户的动作才变为可能。
好吧，教程结束之后你最好作个练习：为不同的系统属性编写一个JSP用来输出由System.getProperty返回的数值，比如java.version、java.home、os.name、user.home以及user.dir等等。
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