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('\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() != 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>