jsp <%! %> 与 <% %> 区别
<body><%!//1、可定义方法public String outMethod(){return "outMethod";}//2、可定义static方法public static String outStaticMethod(){return "outStaticMethod";}//3、可定义static属性public static int count = 0;//4、不可以使用out对象%><%//1、不可定义方法//2、不可定义static方法//3、不可定义static属性//可以使用out对象out.print(outMethod());out.print("<br>");out.print(outStaticMethod());out.print("<br>");out.print(count);%></body>?
经Tomcat编译后，生成的java文件如下：
package org.apache.jsp;import javax.servlet.*;import javax.servlet.http.*;import javax.servlet.jsp.*;public final class test_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent {//1、可定义方法public String outMethod(){return "outMethod";}//2、可定义static方法public static String outStaticMethod(){return "outStaticMethod";}//3、可定义static属性public static int count = 0;//4、不可以使用out对象 private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory(); private static java.util.List _jspx_dependants; private javax.el.ExpressionFactory _el_expressionfactory; private org.apache.AnnotationProcessor _jsp_annotationprocessor; public Object getDependants() { return _jspx_dependants; } public void _jspInit() { _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor.class.getName()); } public void _jspDestroy() { } public void _jspService(HttpServletRequest request, HttpServletResponse response) throws java.io.IOException, ServletException { PageContext pageContext = null; HttpSession session = null; ServletContext application = null; ServletConfig config = null; JspWriter out = null; Object page = this; JspWriter _jspx_out = null; PageContext _jspx_page_context = null; try { response.setContentType("text/html; charset=utf-8"); pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true); _jspx_page_context = pageContext; application = pageContext.getServletContext(); config = pageContext.getServletConfig(); session = pageContext.getSession(); out = pageContext.getOut(); _jspx_out = out; out.write("\r\n"); out.write("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\r\n"); out.write("<html>\r\n"); out.write("<head>\r\n"); out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\">\r\n"); out.write("<title>Insert title here</title>\r\n"); out.write("</head>\r\n"); out.write("<body>\r\n"); out.write("\r\n"); out.write("\r\n");//1、不可定义方法//2、不可定义static方法//3、不可定义static属性//可以使用out对象out.print(outMethod());out.print("<br>");out.print(outStaticMethod());out.print("<br>");out.print(count); out.write("\r\n"); out.write("</body>\r\n"); out.write("</html>"); } catch (Throwable t) { if (!(t instanceof SkipPageException)){ out = _jspx_out; if (out != null && out.getBufferSize() != 0) try { out.clearBuffer(); } catch (java.io.IOException e) {} if (_jspx_page_context != null) _jspx_page_context.handlePageException(t); } } finally { _jspxFactory.releasePageContext(_jspx_page_context); } }}?
在生成的java文件中，我们可以看到，<%! %>中的代码对应于java类文件的成员方法、静态方法，静态变量，而<%? %>中的代码对应于java类文件的_jspService方法中的代码（_jspService对应于servlet中的service方法），这也就是为什么在<% %>中不能声明方法、静态变量的原因了（方法中是不可以再创建方法的）。
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http://huangqiqing123.iteye.com/blog/1922014
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