在一个JSP页面中，有如下代码，请问最终的输出结果为：

1     <%! int i = 1;%>2     <%! int getNumber(){3         return i;4     }%>5     <% int i = 10;6         out.println("first i = "+i);%>7     <% out.println("second i = "+i);%>8     <% out.println("third i = "+getNumber());%>

    其输出结果为：first i = 10  second i = 10 third i = 1

   这道题容易出错的原因是在于分不清在<%! %>声明语句中声明的变量和在<% %>小脚本中声明的变量的区别，它们两个区别具体如下：JSP声明语句中声明的变量在生成Servlet后位于类的成员变量部分，属于全局变量；而JSP脚本段声明的变量在生成Servlet后位于service方法中，属于局部变量，当方法运行完后就被销毁了。Servlet是一个单实例对象，成员变量只有一个，每个用户都可访问到它，所以会污染全局变量，在多用户访问时，也不利于维护数据的正确性和安全性。

   其实 我们可以从jsp生成的.java文件看出区别，从源代码可以看出这个jsp页面程序到底是怎么执行的：

1 package org.apache.jsp;  2   3 import javax.servlet.*;  4 import javax.servlet.http.*;  5 import javax.servlet.jsp.*;  6   7 public final class test_jsp extends org.apache.jasper.runtime.HttpJspBase  8     implements org.apache.jasper.runtime.JspSourceDependent {  9  //JSP声明语句声明的变量和方法，在全局部分 10  int i = 1; 11  int getNumber(){ 12         return i; 13     } 14   private static final javax.servlet.jsp.JspFactory _jspxFactory = 15           javax.servlet.jsp.JspFactory.getDefaultFactory(); 16  17   private static java.util.Map
      
        _jspx_dependants; 18  19   private volatile javax.el.ExpressionFactory _el_expressionfactory; 20   private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager; 21  22   public java.util.Map
       
         getDependants() { 23     return _jspx_dependants; 24   } 25  26   public javax.el.ExpressionFactory _jsp_getExpressionFactory() { 27     if (_el_expressionfactory == null) { 28       synchronized (this) { 29         if (_el_expressionfactory == null) { 30           _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); 31         } 32       } 33     } 34     return _el_expressionfactory; 35   } 36  37   public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() { 38     if (_jsp_instancemanager == null) { 39       synchronized (this) { 40         if (_jsp_instancemanager == null) { 41           _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); 42         } 43       } 44     } 45     return _jsp_instancemanager; 46   } 47  48   public void _jspInit() { 49   } 50  51   public void _jspDestroy() { 52   } 53   //JSP页面生成的Service方法，小脚本语句位于这个方法中 54   public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response) 55         throws java.io.IOException, javax.servlet.ServletException { 56  57     final javax.servlet.jsp.PageContext pageContext; 58     javax.servlet.http.HttpSession session = null; 59     final javax.servlet.ServletContext application; 60     final javax.servlet.ServletConfig config; 61     javax.servlet.jsp.JspWriter out = null; 62     final java.lang.Object page = this; 63     javax.servlet.jsp.JspWriter _jspx_out = null; 64     javax.servlet.jsp.PageContext _jspx_page_context = null; 65  66  67     try { 68       response.setContentType("text/html;charset=UTF-8"); 69       pageContext = _jspxFactory.getPageContext(this, request, response, 70                   null, true, 8192, true); 71       _jspx_page_context = pageContext; 72       application = pageContext.getServletContext(); 73       config = pageContext.getServletConfig(); 74       session = pageContext.getSession(); 75       out = pageContext.getOut(); 76       _jspx_out = out; 77  78       out.write("\r\n"); 79       out.write("\r\n"); 80       out.write("\r\n"); 81       out.write("\r\n"); 82       out.write("    
        \r\n"); 83       out.write("\r\n"); 84       out.write("\r\n"); 85       out.write("    "); 86       out.write("\r\n"); 87       out.write("    "); 88       out.write("\r\n"); 89       out.write("    "); 90       //JSP小脚本中声明的变量 91       int i = 10; 92       //JSP小脚本中的语句 93         out.println("first i = "+i); 94       out.write("\r\n"); 95       out.write("    "); 96       //JSP小脚本中的语句 97  out.println("second i = "+i); 98       out.write("\r\n"); 99       out.write("    ");100       //JSP小脚本中的语句101  out.println("third i = "+getNumber());102       out.write("\r\n");103       out.write("\r\n");104       out.write("\r\n");105     } catch (java.lang.Throwable t) {106       if (!(t instanceof javax.servlet.jsp.SkipPageException)){107         out = _jspx_out;108         if (out != null && out.getBufferSize() != 0)109           try {110             if (response.isCommitted()) {111               out.flush();112             } else {113               out.clearBuffer();114             }115           } catch (java.io.IOException e) {}116         if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);117         else throw new ServletException(t);118       }119     } finally {120       _jspxFactory.releasePageContext(_jspx_page_context);121     }122   }123 }