700字范文 > 演示JSP Scriptlets 声明语句 jsp表达式的使用

演示JSP Scriptlets 声明语句 jsp表达式的使用

时间：2023-06-29 21:33:53

一、创建example01.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>JSP脚本元素</title></head><%!int a = 1, b = 2; //定义两个变量a,b%><%!public String print() { //定义print方法String str = "itcast"; //方法内定义的变量strreturn str;}%><body><%out.println(a + b); //输出两个变量的和 -->%> <%out.println(print());//调用print()方法，输出其返回值 %> <%=a+b %> <%=print() %></body></html>

二、启动项目并访问

http://localhost:8080/chapter06/example01.jsp

三、总结

1.<%! %> 用来定义成员变量和方法，不可以进行输出的。

2.<% %> 主要用来输出内容的，可以定义局部变量，jsp转换为Servlet时，被放在_jspService()方法内。

3.<%= %> 里面是表达式，不是语句，对应out.print(表达式);

四、源码

/** Generated by the Jasper component of Apache Tomcat* Version: Apache Tomcat/9.0.31* Generated at: -09-27 14:38:46 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 example01_jsp extends org.apache.jasper.runtime.HttpJspBaseimplements org.apache.jasper.runtime.JspSourceDependent,org.apache.jasper.runtime.JspSourceImports {int a = 1, b = 2; //定义两个变量a,bpublic String print() { //定义print方法String str = "itcast"; //方法内定义的变量strreturn str;}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 {if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {final java.lang.String _jspx_method = request.getMethod();if ("OPTIONS".equals(_jspx_method)) {response.setHeader("Allow","GET, HEAD, POST, OPTIONS");return;}if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {response.setHeader("Allow","GET, HEAD, POST, OPTIONS");response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");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("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \r\n");out.write(" \"/TR/html4/loose.dtd\">\r\n");out.write("<html>\r\n");out.write("<head>\r\n");out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n");out.write("<title>JSP脚本元素</title>\r\n");out.write("</head>\r\n");out.write('\r');out.write('\n');out.write("\r\n");out.write("<body>\r\n");out.write("\r\n");out.write("\t");out.println(a + b); //输出两个变量的和 -->out.write(" \r\n");out.write(" \t \r\n");out.write("\t");out.println(print());//调用print()方法，输出其返回值 out.write(" \r\n");out.write("\t \r\n");out.write("\t");out.print(a+b );out.write(" \r\n");out.write("\t");out.print(print() );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);}}}

本内容不代表本网观点和政治立场，如有侵犯你的权益请联系我们处理。

网友评论

网友评论仅供其表达个人看法，并不表明网站立场。