Java for Web学习笔记（二八）：JSTL（4）Core Tag（下）

xiaoxiao2026-01-02 3

给个例子来复习一下，模拟地址本显示。

联系人类：Contact

这里顺便学些一下自动排序的做法，定义Contact类，实现Comparable接口。Contact是个简单的POJO，getter和setter从略。此外MonthDay和Instant是Java 8增加的时间处理类。

public class Contact implements Comparable<Contact>{ private String firstName; private String lastName; private String phoneNumber; private String address; private MonthDay birthday; private Instant dateCreated; public Contact() { } public Contact(String firstName, String lastName, String phoneNumber, String address, MonthDay birthday,Instant dateCreated) { ...... } ..setters 和 getters.... @Override public int compareTo(Contact other) { int last = lastName.compareTo(other.lastName); if(last == 0){ return firstName.compareTo(other.firstName); } return last; } }

Servlet：将数据传递给jsp文件

ListServlet如下。一般而言，应该将jsp隐藏到/WEB-INF这个安全目录下，而不是在外面可直接读取的位置。

@WebServlet(name = "ListServlet", urlPatterns = "/list") public class ListServlet extends HttpServlet { private static final long serialVersionUID = 1L; /* Contact类实现了排序接口Comparable，在此我们定义排序Set，采用TreeSet方式*/ private static final SortedSet<Contact> contacts = new TreeSet<>(); /* 预设数据，模拟地址本*/ static{ contacts.add(new Contact("Flowingflying", "Wei", "13312345678", "Guangzhou", MonthDay.of(Month.MAY, 20),Instant.parse("2016-08-05T21:34:12Z"))); contacts.add(new Contact("John", "Smith", "17712345678", "Guangxi", MonthDay.of(Month.APRIL, 21),Instant.parse("2016-08-04T20:31:13Z"))); contacts.add(new Contact( "Peter", "Smith", "555-0712", "315 Maple St", null,Instant.parse("2012-10-15T15:31:17Z"))); } ... ... /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if(request.getParameter("empty") != null){/* 为了jsp测试，传递一个空的地址本过去 */ request.setAttribute("contacts", Collections.<Contact>emptySet()); }else{/* 传递地址本信息过去 */ request.setAttribute("contacts", contacts); } /* 跳转到jsp中，注意jsp存放的路径*/ request.getRequestDispatcher("/WEB-INF/jsp/view/list.jsp").forward(request, response); } }

jsp：跳转

index.jsp跳转至/list

<c:redirect url="/list" />

在base.jspf中已经给出引入：

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

web.xm有如下信息：

<jsp-config> <jsp-property-group> <url-pattern>*.jsp</url-pattern> <url-pattern>*.jspf</url-pattern> <page-encoding>UTF-8</page-encoding> <scripting-invalid>false</scripting-invalid> <include-prelude>/WEB-INF/jsp/base.jspf</include-prelude> <trim-directive-whitespaces>true</trim-directive-whitespaces> <default-content-type>text/html</default-content-type> </jsp-property-group> </jsp-config>

但是，在Eclipse有个问题，如果我们不在本文件中给出taglib，那么jsp就不能自动使用智能拼词，并出现warning，这个是很讨厌的，所以我喜欢在jsp中多写两行，引入tablib。

jsp：list.jsp显示信息

<%--@elvariable id="contacts" type="java.util.Set<cn.wei.flowingflying.chapter07.Contact>" --%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>List</title> </head> <body> <h2>Address Book Contacts</h2> <c:choose><-- 如果信息为空如何，不为空如何 --> <c:when test="${fn:length(contacts) == 0}"> There are no contacts in the address book. </c:when> <c:otherwise> There are ${fn:length(contacts)} contacts in the address book.<br/> <c:forEach items="${contacts}" var="contact"> <c:out value="${contact.lastName},${contact.firstName}"/><br/>   <c:out value="${contact.phoneNumber}"/><br/> <c:out value="${contact.address}"/><br/> <c:if test="${contact.birthday != null}"> BirthDay: ${contact.birthday}<br/> </c:if> Created:${contact.dateCreated}<br/><br/> </c:forEach> </c:otherwise> </c:choose> </body> </html>

相关链接：我的Professional Java for Web Applications相关文章

转载请注明原文地址: https://ju.6miu.com/read-1305568.html

最新回复(0)