jsp的一些基本语法

时间：2021-11-27 15:53:58

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="">

    <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, , true);

      _jspx_page_context = pageContext;

      application = pageContext.getServletContext();

      config = pageContext.getServletConfig();

      session = pageContext.getSession();

      out = pageContext.getOut();

      _jspx_out = out;

      out.write('\r');

      out.write('\n');

String path = request.getContextPath();

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

      out.write("\r\n");

      out.write("\r\n");

      out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");

      out.write("<html>\r\n");

      out.write("  <head>\r\n");

      out.write("    <base href=\"");

      out.print(basePath);

      out.write("\">\r\n");

      out.write("    \r\n");

      out.write("    <title>My JSP 'index.jsp' starting page</title>\r\n");

      out.write("    \r\n");

      out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");

      out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");

      out.write("\t<meta http-equiv=\"expires\" content=\"0\">    \r\n");

      out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");

      out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");

      out.write("\t<!--\r\n");

      out.write("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");

      out.write("\t-->\r\n");

      out.write("\r\n");

      out.write("  </head>\r\n");

      out.write("  \r\n");

      out.write("  <body>\r\n");

      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 -->\r\n");

      out.write("  ");

      out.write("\r\n");

      out.write("    ");

    Date date=new Date();

    String time=date.toLocaleString();

    out.write(time);

      out.write("\r\n");

      out.write("     <br>\r\n");

      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 -->\r\n");

      out.write("     \r\n");

      out.write("     ");

for(int i=0;i<5;i++){

      out.write("\r\n");

      out.write("     hello for\r\n");

      out.write("     ");

}

      out.write("\r\n");

      out.write("     \r\n");

      out.write("     ");

      out.write("\r\n");

      out.write("  </body>\r\n");

      out.write("</html>\r\n");

    } catch (java.lang.Throwable t) {

      if (!(t instanceof javax.servlet.jsp.SkipPageException)){

        out = _jspx_out;

        if (out != null && out.getBufferSize() != )

          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>/.html</url-pattern>

    </servlet-mapping>

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