1.jsp脚本 (3种代码块)
1.<% JAVA代码块 %>
2.<%= JAVA变量或者表达式%>
3.<%! JAVA代码块%>
方法1:<% java代码 %>
特点:内部的java代码直接翻译到Servlet方法内部
如图所示:
jsp窗口:
jsp生成的Servlet窗口:
方法2:<%= java变量或者表达式 %>
特点:相当于out.print(java变量或者表达式)
jsp窗口:
jsp生成的Servlet窗口:
方法3:<%! java代码 %>
特点:存放在Servlet方法块里
jsp窗口:
jsp生成的Servlet窗口:
index.jsp代码
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>我的网页</title>
</head>
<body>
<%int i=0;out.print(i);
%>
<%=i+3
%>
<%!public class Student{int age;String name;public Student(String name,int age) {this.age = age;this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "Student{" + "age=" + age + ", name='" + name + '\'' + '}';}}
%><%Student me = new Student("神奇的我", 12);out.println(me.toString());
%>
</body>
</html>生成的index_jsp.java 代码 （具体可以在Tomcat的work下找到）
/** Generated by the Jasper component of Apache Tomcat* Version: Apache Tomcat/9.0.1* Generated at: 2017-12-03 14:54:33 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.web;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;public final class index_jsp extends org.apache.jasper.runtime.HttpJspBaseimplements org.apache.jasper.runtime.JspSourceDependent,org.apache.jasper.runtime.JspSourceImports {public class Student{int age;String name;public Student(String name,int age) {this.age = age;this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "Student{" + "age=" + age + ", name='" + name + '\'' + '}';}}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 {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("\n");out.write("\n");out.write("<html>\n");out.write("<head>\n");out.write("<title>我的网页</title>\n");out.write("</head>\n");out.write("<body>\n");int i=0;out.print(i);out.write('\n');out.print(i+3);out.write('\n');out.write('\n');out.write('\n');Student me = new Student("神奇的我", 12);out.println(me.toString());out.write("\n");out.write("\n");out.write('\n');out.write("\n");out.write("</body>\n");out.write("</html>\n");} 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);}}
}
