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.HttpJspBaseimplements 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('\r');out.write('\n');String path = request.getContextPath();String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";pageContext.setAttribute("pca", "pageContextAttribute");out.write("\r\n");out.write("<!DOCTYPE html>\r\n");out.write("<html>\r\n");out.write("<head>\r\n");out.write("<meta charset=\"UTF-8\">\r\n");out.write("<title>009index</title>\r\n");out.write("</head>\r\n");out.write("<body>\r\n");out.write("\t");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("\r\n");out.write("\t\t");org.apache.jasper.runtime.JspRuntimeLibrary.introspecthelper(_jspx_page_context.findAttribute("person"), "name", "stono", null, null, false);out.write('\r');out.write('\n');out.write('    ');}out.write('\r');out.write('\n');out.write('    ');out.write(org.apache.jasper.runtime.JspRuntimeLibrary.toString((((com.stono.servlet.bean.Person)_jspx_page_context.findAttribute("person")).getName())));out.write("\r\n");out.write("\t\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);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 causeorg.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 causejava.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 causeorg.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 exceptionjava.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>&lt;%@ page import="com.stono.servlet.bean.*" %&gt;&lt;%Person person33 = new Employee();person33.setName("stono3inJsp");pageContext.setAttribute("person3", person33);%&gt&lt;jsp:useBean id="person3" type="com.stono.servlet.bean.Person"&gt&lt;/jsp:useBean&gt&lt;jsp:getProperty property="name" name="person3"/&gt</pre></p>
</body>
</html>

转载于:https://www.cnblogs.com/stono/p/4894445.html

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