黑马总结：el表达式${user.address.contact.mobileTelephone}为什么可以实现输出属性值

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下面的代码可以用来实现，jsp为什么就是一个servlet的特点。<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%@page import="org.skycn.tianzhw.entity.*"%><%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><%@taglib uri="http://www.skycn.com" prefix="tianzhw"%><%Contact contact = new Contact();Address address = new Address();Teacher teacher = new Teacher();User user = new User();contact.setMobileTelephone("1234560956870-983498572345");contact.setEMail("tianzhw@vip.qq.com");user.setName("zhongguo");user.setAge("12");user.setAddress(address);user.setTeacher(teacher);teacher.setName("zxx");teacher.setAge("20");teacher.setAddress(address);address.setArea("beijing");address.setCity("beijing");address.setContact(contact);address.setProvince("hebei");request.setAttribute("user",user);session.setAttribute("teacher",teacher);application.setAttribute("name","nihao shijie"); %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><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"></head><body>" ${user.address.contact.mobileTelephone} <br><%=org.skycn.tianzhw.AnalyseBean.analyse("${user.teacher.name}",pageContext) %><br>${tianzhw:test("成功") }</body></html>

上面的页面，是一个数据准备阶段。

package org.skycn.tianzhw;import java.lang.reflect.InvocationTargetException;import javax.servlet.ServletContext;import javax.servlet.ServletRequest;import javax.servlet.http.HttpSession;import javax.servlet.jsp.PageContext;import com.sun.org.apache.commons.beanutils.BeanUtils;import com.sun.org.apache.commons.beanutils.MethodUtils;import com.sun.org.apache.commons.beanutils.PropertyUtils;public class AnalyseBean {private String src;private PageContext context;public AnalyseBean(String src, PageContext context) {this.src = src;this.context = context;}public static Object analyse(String src, PageContext context) {//截取字符串int _tempOne = src.indexOf("{");int _tempTwo = src.indexOf("}");src = src.substring(_tempOne + 1, _tempTwo);//以"."为分隔符，截取字符串String[] strs = src.split("//.");int size = strs.length;//获得全部作用域对象 ServletRequest request = context.getRequest();HttpSession session = context.getSession();ServletContext servlet = context.getServletContext();//无论字符串的长度是多长，这里面不考虑字符为null，或者格式不正确的错误。 Object res = null;Object obj = context.getAttribute(strs[0]);if (null == obj) {obj = request.getAttribute(strs[0]);if (null == obj) {obj = session.getAttribute(strs[0]);if (null == obj) {obj = servlet.getAttribute(strs[0]);if (null == obj) {throw new RuntimeException("net exist Object in any airspace");}}}}//思路：如果String数组的长度是2，那么就一定是一个对象的一个属性值，长度是3，就是说一个对象中包涵一个自定义对象的属性值。。。。。。那么//那么如果有N个长度，就是有N-1个对象的属性值。try {//长度小于2的时候，直接就是在全部作用域中查找，返回这个属性 if( 2 > size ){return obj;}if (2 == size) {res = BeanUtils.getProperty(obj, strs[1]);}//思路：定义一个控制变量i，初始化值为1，当size大于2的时候，数组strs[size - 1]一定是最后的一个对象。if (2 < size) {int i = 1;Object obj2 = null ;while (!((size - i)==1)){obj2 = PropertyUtils.getProperty(obj, strs[i]);obj = obj2 ;i++;} res = BeanUtils.getProperty(obj2, strs[size - 1]);}} catch (IllegalAccessException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (InvocationTargetException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (NoSuchMethodException e) {// TODO Auto-generated catch blocke.printStackTrace();}return res;}}

上面的代码，就是如何实现的类。有更加方便的实现方法，我的这个类里面实现了，使用beanUtils支持。