java web基础 --- forEach标签

testtag.jsp

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>







	
JSP标签测试
	
	 	

		

			
姓名
			
职业
			
年龄
		
	

	 		

	 		

	 		

	 	
	
	

SimpleFormServlet.java

package com.web1.hello;


import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.web1.datamodel.Pserson;

/**
 * Servlet implementation class SimpleFormServlet
 */
@WebServlet("/SimpleFormServlet")
public class SimpleFormServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SimpleFormServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
			throws ServletException, IOException {
		request.setAttribute("jspcontent", "I am JSP");
		String formPage = "/pages/result.jsp";
		
		request.setAttribute("name_str", request.getParameter("name_str"));
		request.setAttribute("occyp_str", request.getParameter("occyp_str"));
		request.setAttribute("age_num", request.getParameter("age_num"));
		
		RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(formPage);
		dispatcher.forward(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) 
			throws ServletException, IOException {
		String formPage = "/pages/testtag.jsp";
		
		Pserson person1 = new Pserson();
		person1.setName("张三");
		person1.setOccupy("工程师");
		person1.setAge(22);
		Pserson person2 = new Pserson();
		person2.setName("李四");
		person2.setOccupy("教师");
		person2.setAge(24);
		Pserson person3 = new Pserson();
		person3.setName("王五");
		person3.setOccupy("程序猿");
		person3.setAge(27);
		
		List pList = new ArrayList();
		pList.add(person1);
		pList.add(person2);
		pList.add(person3);
		
		request.setAttribute("pList", pList);
		RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(formPage);
		dispatcher.forward(request, response);
	}

}

正确配置Jstl的Maven依赖

原文：http://www.javacoder.cn/?p=195

在jsp 中使用el表达式都好几年了，原来都是将需要的jar直接放在WEB-INF/lib目录下，最近转向maven构建。一下子各种问题。
detail.jsp 的内容如下：
<%@ page language=”java”  pageEncoding=”UTF-8″%>
<%@ page isELIgnored =”false” %>
<%@ taglib uri=”http://java.sun.com/jsp/jstl/core” prefix=”c” %>


运行时提示：
ClassNotFoundException: javax.servlet.jsp.jstl.core.Config
网上搜索一番，
说是jstl 需要手动引入，于是在pom.xml中添加依赖如下：

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< dependency >              < groupId > javax . servlet . jsp . jstl < / groupId >              < artifactId > jstl - api < / artifactId >              < version > 1.2 < / version >      < / dependency >

再次运行：错误如下：
java.lang.NoClassDefFoundError: org/apache/taglibs/standard/tag/rt/core/Out
刚才我们只是导入了jstl-api，而没有导入jstl的实现，所以再导入jstl 的实现。去mvnrepository上找jstl 的实现，基本上有两个版本，一个是glassfish 的jstl-impl, 另一个是apache的taglibs-standard-impl，一直犹豫不决该用谁，最后在stackoverflow.com/a/25374024/1443527上发现网友分享了他实现的经验，他用的是glassfish版本，所以我们也引人这个。由于tomcat7是兼容j2ee 3.0规范的，所以我们将jstl 依赖的东西给去除掉，防止和tomcat自身的servlet jar包冲突，改正后的依赖为

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< dependency >              < groupId > javax . servlet . jsp . jstl < / groupId >              < artifactId > jstl - api < / artifactId >              < version > 1.2 < / version >              < exclusions >                  < exclusion >                      < groupId > javax . servlet < / groupId >                      < artifactId > servlet - api < / artifactId >                  < / exclusion >                  < exclusion >                      < groupId > javax . servlet . jsp < / groupId >                      < artifactId > jsp - api < / artifactId >                  < / exclusion >              < / exclusions >          < / dependency >            < dependency >              < groupId > org . glassfish . web < / groupId >              < artifactId > jstl - impl < / artifactId >              < version > 1.2 < / version >              < exclusions >                  < exclusion >                      < groupId > javax . servlet < / groupId >                      < artifactId > servlet - api < / artifactId >                  < / exclusion >                  < exclusion >                      < groupId > javax . servlet . jsp < / groupId >                      < artifactId > jsp - api < / artifactId >                  < / exclusion >                  < exclusion >                      < groupId > javax . servlet . jsp . jstl < / groupId >                      < artifactId > jstl - api < / artifactId >                  < / exclusion >              < / exclusions >          < / dependency >

哈哈，运行正确。

顺便说一下jstl-impl-1.2.jar 和taglibs-standard-impl-1.2.1.jar 的区别，这两个包的内容很相似，后者应该是前者的一个再打包，因为Apache的taglibs工程从2009年以后一直处于停止状态。

如果你要引人后者，那么依赖应该为：

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< dependency >        < groupId > org . apache . taglibs < / groupId >        < artifactId > taglibs - standard - spec < / artifactId >        < version > 1.2.1 < / version >      < / dependency >      < dependency >        < groupId > org . apache . taglibs < / groupId >        < artifactId > taglibs - standard - impl < / artifactId >        < version > 1.2.1 < / version >      < / dependency >

顺便提一下：你知道web.xml配置中的url-pattern的‘/’和‘/*’的区别吗？
哎，基本功不扎实，这个问题折腾了好久。‘/’表示该项目的所有请求路径；‘/*’表示只能有一级子路径，它匹配’/a.jsp’但是不匹配‘/jsp/a.jsp’。