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  • jsp的一些基本语法

    jsp页面内容

    <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
  <%! public void a(){} %> <!-- 通过声明， 可在servlet中定义方法，注意前面的"!"符合 -->
  <%! static{System.out.println("static");} %>
    <% 
    Date date=new Date();
    String time=date.toLocaleString();
    out.write(time);
     %>
     <br>
     <%=time%> <!-- 脚本表达式，用于向浏览器输出数据 -->
     
     <%for(int i=0;i<5;i++){ %>
     hello for
     <%} %>
     
     <%-- jsp注释内容 --%>
  </body>
</html>

    生成servlet的内容：

    package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {

 public void a(){} 
 static{System.out.println("static");} 
  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();

  private static java.util.List<java.lang.String> _jspx_dependants;

  private javax.el.ExpressionFactory _el_expressionfactory;
  private org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.List<java.lang.String> getDependants() {
    return _jspx_dependants;
  }

  public void _jspInit() {
    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
  }

  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 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('
');
      out.write('
');

String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

      out.write("
");
      out.write("
");
      out.write("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
");
      out.write("<html>
");
      out.write("  <head>
");
      out.write("    <base href="");
      out.print(basePath);
      out.write("">
");
      out.write("    
");
      out.write("    <title>My JSP 'index.jsp' starting page</title>
");
      out.write("    
");
      out.write("	<meta http-equiv="pragma" content="no-cache">
");
      out.write("	<meta http-equiv="cache-control" content="no-cache">
");
      out.write("	<meta http-equiv="expires" content="0">    
");
      out.write("	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
");
      out.write("	<meta http-equiv="description" content="This is my page">
");
      out.write("	<!--
");
      out.write("	<link rel="stylesheet" type="text/css" href="styles.css">
");
      out.write("	-->
");
      out.write("
");
      out.write("  </head>
");
      out.write("  
");
      out.write("  <body>
");
      out.write("  ");
      out.write(" <!-- 閫氳繃澹版槑锛?鍙�湪servlet涓�畾涔夋柟娉曪紝娉ㄦ剰鍓嶉潰鐨刓"!"绗﹀悎 -->
");
      out.write("  ");
      out.write("
");
      out.write("    ");
 
    Date date=new Date();
    String time=date.toLocaleString();
    out.write(time);
     
      out.write("
");
      out.write("     <br>
");
      out.write("     ");
      out.print(time);
      out.write(" <!-- 鑴氭湰琛ㄨ揪寮忥紝鐢ㄤ簬鍚戞祻瑙堝櫒杈撳嚭鏁版嵁 -->
");
      out.write("     
");
      out.write("     ");
for(int i=0;i<5;i++){ 
      out.write("
");
      out.write("     hello for
");
      out.write("     ");
} 
      out.write("
");
      out.write("     
");
      out.write("     ");
      out.write("
");
      out.write("  </body>
");
      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 { out.clearBuffer(); } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

    包含页面

    <%@ include file="/public/head.jsp" %>  静态包含
    <% request.getRequestDispatcher("/public/head.jsp").include(request, response); %>  动态包含

    如果是错误页面，可标记为错误页面，将可获取到错误信息。

    <%@ page language="java" import="java.util.*" isErrorPage="true" pageEncoding="UTF-8"%>

    <%
    String message = exception.getMessage();
    out.write(message);
    %>

     以下代码将先输出 haha 再输出 message ,因为数据最终都是通过response.getWriter()输出的，out.write()相当于另外一个缓冲区，out.write()执行

    完后将再进入response缓冲区，最后再将response的数据发给tomcat执行输出。

    <%
    String message = exception.getMessage();
    out.write(message);
    response.getWriter().write("haha");
%>

     pageContext封装了所有域对象，经常用在自定义标签

        <%
        request.setAttribute("data", "aaa");
        pageContext.setAttribute("data", "bbb",PageContext.REQUEST_SCOPE);
        String data = (String) pageContext.getAttribute("data",
                PageContext.REQUEST_SCOPE);
        out.write(data);
        
        String data2=(String)pageContext.findAttribute("data");
        out.write(data2);
    %>
    ${data} <%-- el表达式 --%>
    
    <% pageContext.forward("/index2.jsp"); %>
    <% pageContext.include("/public/head.jsp"); %>

    常用jsp标签

    <jsp:forward page="/index2.jsp"></jsp:forward>
<jsp:include page="/public/head.jsp"></jsp:include>  <!-- 动态标签 -->
    <jsp:forward page="/servlet/testServlet?data2=123"> 
         <jsp:param value="value" name="data" /> 
    </jsp:forward>


    取参数

    String data=(String)request.getParameter("data");

    System.out.println("data:"+data);

    String data2=(String)request.getParameter("data2");
    System.out.println("data2:"+data2);

    将jsp页面映射到servlet

        <servlet>
        <servlet-name>xxx</servlet-name>
        <jsp-file>/index3.jsp</jsp-file>
    </servlet>
    <servlet-mapping>
        <servlet-name>xxx</servlet-name>
        <url-pattern>/1.html</url-pattern>
    </servlet-mapping>
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  • 原文地址：https://www.cnblogs.com/zhuawang/p/3404830.html
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