（四）JSP语法详细介绍--脚本元素

时间 2019-11-10

标签 jsp 语法详细介绍脚本元素栏目 JSP 繁體版

原文原文链接

经过scriptlet能够在jsp中嵌入java代码html

<%! 代码片断 %> //能够定义全局变量/方法/类
<% 代码片断 %>  //能够定义局部变量/方法/类
<%= %>          //输出一个变量或具体内容（等同于<% out.println("变量或具体内容"); %>）

也能够用如下XML语句代替：java

<jsp:scriptlet>
   代码片断
</jsp:scriptlet>

示例以下：express

1 jsp代码：apache

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<html>
	<head>
		<title>life.jsp</title>
	</head>
	<body>
		<h1>测试实例</h1>
		<%!
		private String str1 = "全局变量";
		
		public void testA() {
			System.out.println("全局方法");
		}
		
		class c{
			public c(){
				System.out.println("全局类");
			}
		}
		%>
	
		<%
			String str2 = "局部变量";
			out.println(str2);
		%>		
	</body>
</html>

2 jsp 页面编译获得的 Java类代码:tomcat

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,
                 org.apache.jasper.runtime.JspSourceImports {
		private String str1 = "全局变量";
		
		public void testA() {
			System.out.println("全局方法");
		}
		
		class c{
			public c(){
				System.out.println("全局类");
			}
		}
		
  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.jsp");
    _jspx_imports_packages.add("javax.servlet.http");
    _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=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("<html>\r\n");
      out.write("\t<head>\r\n");
      out.write("\t\t<title>life.jsp</title>\r\n");
      out.write("\t</head>\r\n");
      out.write("\t<body>\r\n");
      out.write("\t\t<h1>测试实例</h1>\r\n");
      out.write("\t\t");
      out.write("\r\n");
      out.write("\t\r\n");
      out.write("\t\t");
			String str2 = "局部变量";
			out.println(str2);
		
      out.write("\t\t\r\n");
      out.write("\t</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);
    }
  }
}