JSP声明实战

今天药忘吃喽~ 2021-07-24 18:40 423阅读 0赞

**一 代码**

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title> 声明示例 </title>
        <meta name="website" content="http://www.crazyit.org" />
    </head>
    
    <%!
    //声明一个整形变量
    public int count;
    //声明一个方法
    public String info()
    {
        return "hello";
    }
    %>
    <body>
    <%
    //将count的值输出后再加1
    out.println(count++);
    %>
    <br/>
    <%
    //输出info()方法的返回值
    out.println(info());
    %>
    </body>
    </html>

**二 运行**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

**三 说明**

该JSP对应的Servlet代码如下，声明的变量和方法变成了Servlet类declare\_jsp的成员变量和成员方法。

/*
    * Generated by the Jasper component of Apache Tomcat
    * Version: Apache Tomcat/8.5.43
    * Generated at: 2019-09-02 12:21:19 UTC
    * Note: The last modified time of this file was set to
    *       the last modified time of the source file after
    *       generation to assist with modification tracking.
    */
    package org.apache.jsp;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.jsp.*;
    
    public final class declare_jsp extends org.apache.jasper.runtime.HttpJspBase
        implements org.apache.jasper.runtime.JspSourceDependent,
                     org.apache.jasper.runtime.JspSourceImports {
    
    
    //声明一个整形变量
    public int count;
    //声明一个方法
    public String info()
    {
        return "hello";
    }
    
      private static final javax.servlet.jsp.JspFactory _jspxFactory =
              javax.servlet.jsp.JspFactory.getDefaultFactory();
    
      private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;
    
      private static final java.util.Set<java.lang.String> _jspx_imports_packages;
    
      private static final java.util.Set<java.lang.String> _jspx_imports_classes;
    
      static {
        _jspx_imports_packages = new java.util.HashSet<>();
        _jspx_imports_packages.add("javax.servlet");
        _jspx_imports_packages.add("javax.servlet.http");
        _jspx_imports_packages.add("javax.servlet.jsp");
        _jspx_imports_classes = null;
      }
    
      private volatile javax.el.ExpressionFactory _el_expressionfactory;
      private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;
    
      public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
        return _jspx_dependants;
      }
    
      public java.util.Set<java.lang.String> getPackageImports() {
        return _jspx_imports_packages;
      }
    
      public java.util.Set<java.lang.String> getClassImports() {
        return _jspx_imports_classes;
      }
    
      public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
        if (_el_expressionfactory == null) {
          synchronized (this) {
            if (_el_expressionfactory == null) {
              _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
            }
          }
        }
        return _el_expressionfactory;
      }
    
      public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
        if (_jsp_instancemanager == null) {
          synchronized (this) {
            if (_jsp_instancemanager == null) {
              _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
            }
          }
        }
        return _jsp_instancemanager;
      }
    
      public void _jspInit() {
      }
    
      public void _jspDestroy() {
      }
    
      public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
          throws java.io.IOException, javax.servlet.ServletException {
    
        final java.lang.String _jspx_method = request.getMethod();
        if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
          response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD");
          return;
        }
    
        final javax.servlet.jsp.PageContext pageContext;
        javax.servlet.http.HttpSession session = null;
        final javax.servlet.ServletContext application;
        final javax.servlet.ServletConfig config;
        javax.servlet.jsp.JspWriter out = null;
        final java.lang.Object page = this;
        javax.servlet.jsp.JspWriter _jspx_out = null;
        javax.servlet.jsp.PageContext _jspx_page_context = null;
    
    
        try {
          response.setContentType("text/html; charset=GBK");
          pageContext = _jspxFactory.getPageContext(this, request, response,
                      "", 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("\r\n");
          out.write("\r\n");
          out.write("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\"\r\n");
          out.write("\t\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\r\n");
          out.write("<html xmlns=\"http://www.w3.org/1999/xhtml\">\r\n");
          out.write("<head>\r\n");
          out.write("\t<title> 声明示例 </title>\r\n");
          out.write("\t<meta name=\"website\" content=\"http://www.crazyit.org\" />\r\n");
          out.write("</head>\r\n");
          out.write("\r\n");
          out.write("\r\n");
          out.write("<body>\r\n");
    
    //将count的值输出后再加1
    out.println(count++);
    
          out.write("\r\n");
          out.write("<br/>\r\n");
    
    //输出info()方法的返回值
    out.println(info());
    
          out.write("\r\n");
          out.write("</body>\r\n");
          out.write("</html>");
        } catch (java.lang.Throwable t) {
          if (!(t instanceof javax.servlet.jsp.SkipPageException)){
            out = _jspx_out;
            if (out != null && out.getBufferSize() != 0)
              try {
                if (response.isCommitted()) {
                  out.flush();
                } else {
                  out.clearBuffer();
                }
              } catch (java.io.IOException e) {}
            if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
            else throw new ServletException(t);
          }
        } finally {
          _jspxFactory.releasePageContext(_jspx_page_context);
        }
      }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/e489fd65dd5a40c18d1f23c9f3962db1.png