JSP userBean setProperty getProperty指令使用
javaBean的属性取决于get/set方法，而不是真实的属性名称。
jsp文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; pageContext.setAttribute("pca", "pageContextAttribute"); %> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>009index</title> </head> <body> <jsp:useBean id="person" class="com.stono.servlet.bean.Person"> <jsp:setProperty property="name" name="person" value="stono" /> </jsp:useBean> <jsp:getProperty property="name" name="person" /> </body> </html>
转换的java文件：
/* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/7.0.35 * Generated at: 2015-10-20 04:32:26 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.*; import java.util.*; public final class index009_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent { 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 javax.el.ExpressionFactory _el_expressionfactory; private org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> 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 + "/"; pageContext.setAttribute("pca", "pageContextAttribute"); out.write(" "); out.write("<!DOCTYPE html> "); out.write("<html> "); out.write("<head> "); out.write("<meta charset="UTF-8"> "); out.write("<title>009index</title> "); out.write("</head> "); out.write("<body> "); out.write(" "); com.stono.servlet.bean.Person person = null; person = (com.stono.servlet.bean.Person) _jspx_page_context.getAttribute("person", javax.servlet.jsp.PageContext.PAGE_SCOPE); if (person == null){ person = new com.stono.servlet.bean.Person(); _jspx_page_context.setAttribute("person", person, javax.servlet.jsp.PageContext.PAGE_SCOPE); out.write(" "); out.write(" "); org.apache.jasper.runtime.JspRuntimeLibrary.introspecthelper(_jspx_page_context.findAttribute("person"), "name", "stono", null, null, false); out.write(' '); out.write(' '); out.write(' '); } out.write(' '); out.write(' '); out.write(' '); out.write(org.apache.jasper.runtime.JspRuntimeLibrary.toString((((com.stono.servlet.bean.Person)_jspx_page_context.findAttribute("person")).getName()))); 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); else throw new ServletException(t); } } finally { _jspxFactory.releasePageContext(_jspx_page_context); } } }
JavaBean：
package com.stono.servlet.bean; public class Person { // 对外的属性名称还是name， private String name2; public String getName() { return name2; } public void setName(String name) { this.name2 = name; } }
jsp:userBean的使用：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; pageContext.setAttribute("pca", "pageContextAttribute"); %> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>009index</title> </head> <body> <p> jsp:useBean id="person" class="com.stono.servlet.bean.Person",如果Person是抽象类，会有异常： <pre> 严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [/index013.jsp (line: 14, column: 1) The value for the useBean class attribute com.stono.servlet.bean.Person is invalid.] with root cause org.apache.jasper.JasperException: /index013.jsp (line: 14, column: 1) The value for the useBean class attribute com.stono.servlet.bean.Person is invalid. </pre> </p> <p> 对于抽象类需要使用jsp:useBean id="person" type="com.stono.servlet.bean.Person" class="com.stono.servlet.bean.Employee"进行使用。 </p> <jsp:useBean id="person" type="com.stono.servlet.bean.Person" class="com.stono.servlet.bean.Employee"> <jsp:setProperty property="name" name="person" value="stono" /> </jsp:useBean> <jsp:getProperty property="name" name="person" /> <p> 直接输入jsp:useBean id="person2" type="com.stono.servlet.bean.Person"会报错： <pre> 严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [javax.servlet.ServletException: java.lang.InstantiationException: bean person2 not found within scope] with root cause java.lang.InstantiationException: bean person2 not found within scope </pre> 输入jsp:useBean id="person" type="com.stono.servlet.bean.Person"也是有问题的： <pre> 严重: Servlet.service() for servlet [jsp] in context with path [/TestBootWeb] threw exception [/index013.jsp (line: 35, column: 1) useBean: Duplicate bean name: {0}] with root cause org.apache.jasper.JasperException: /index013.jsp (line: 35, column: 1) useBean: Duplicate bean name: {0} </pre> </p> <p> 在servlet中进行request.setAttribute("person3",person3),但是在jsp中直接写：jsp:useBean id="person3" type="com.stono.servlet.bean.Person"会报错： <pre> 严重: Servlet.service() for servlet jsp threw exception java.lang.InstantiationException: bean person3 not found within scope </pre> 因为默认的scope是page；修改为scope="request"，就可以读取到request传递过来的值； </p> <p> 如果希望使用jsp:useBean id="person3" type="com.stono.servlet.bean.Person",还不能在scriplet中使用名称为person3的变量，需要如下定义使用： <pre> <%@ page import="com.stono.servlet.bean.*" %> <% Person person33 = new Employee(); person33.setName("stono3inJsp"); pageContext.setAttribute("person3", person33); %> <jsp:useBean id="person3" type="com.stono.servlet.bean.Person"></jsp:useBean> <jsp:getProperty property="name" name="person3"/> </pre> </p> </body> </html>