實例
1.要用到 properties屬性文件,定義一個message.properties文件放在WEB-INF目錄下
message.properties
title=hello
body=world
2.定義一個Servlet,初始化的時候加載 屬性文件
InitServlet2.java 只起到初始化作用會被運行
- package com.servlet;
- import java.io.IOException;
- import java.io.InputStream;
- import java.io.PrintWriter;
- import java.util.Properties;
- import javax.servlet.ServletConfig;
- import javax.servlet.ServletContext;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- public class InitServlet2 extends HttpServlet {
- @Override
- public void init(ServletConfig config) throws ServletException {
- Properties ps = new Properties() ;
- ServletContext context = config.getServletContext() ;
- //獲取 message.properties文件的輸入流
- InputStream is = context.getResourceAsStream("/WEB-INF/message.properties");
- try {
- ps.load(is); //把獲取的流加載到 ps對象中
- } catch (IOException e) {
- e.printStackTrace();
- }
- //把ps對象放在 全局的application中,達到共享作用
- context.setAttribute("ps", ps);
- }
- }
對應的web.xml文件,沒有 <servlet-mapping></servlet-mapping>
- <servlet>
- <servlet-name>InitServlet2</servlet-name>
- <servlet-class>com.servlet.InitServlet2</servlet-class>
- <load-on-startup>3</load-on-startup>
- </servlet>
3.創建標籤的處理類 MyTag2.java
對於標籤中涉及到屬性的一定要在處理類中
定義 setXXX , getXXX
- package com.tag;
- import java.io.IOException;
- import java.util.Properties;
- import javax.servlet.jsp.JspException;
- import javax.servlet.jsp.PageContext;
- import javax.servlet.jsp.tagext.TagSupport;
- public class MyTag2 extends TagSupport{
- private String key ;
- public String getKey() {
- return key;
- }
- //接收頁面 傳過來的值 也就是屬性的值比如 key="title"
- public void setKey(String key) {
- this.key = key;
- }
- @Override
- public int doEndTag() throws JspException {
- try {
- Properties ps = (Properties)this.pageContext.getAttribute("ps", PageContext.APPLICATION_SCOPE);
- String message = ps.getProperty(key); // key對應 自動調用 getKey()
- this.pageContext.getOut().println(message);
- } catch (IOException e) {
- e.printStackTrace();
- }
- return EVAL_PAGE;
- }
- }
4.創建標籤庫描述文件 myTag.tld ,如果有屬性tag內要加屬性attribute
- <?xml version="1.0" encoding="UTF-8"?>
- <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
- <taglib>
- <tlib-version>1.0</tlib-version>
- <jsp-version>1.1</jsp-version>
- <short-name>myTag</short-name>
- <uri>/myTag</uri> <!-- 這個是 uri 而不是 url -->
- <tag>
- <name>message</name>
- <tag-class>com.tag.MyTag2</tag-class>
- <body-content>empty</body-content>
- <attribute>
- <name>key</name> <!-- 該屬性的名字 key要和 處理類的成員變量相對應 -->
- <required>true</required> <!-- required = true 說明該屬性是必填的,反之false-->
- </attribute>
- </tag>
- </taglib>
5.JSP頁面
-
<%@page language="java" contentType="test/html;charset=GB2312" pageEncoding="GB2312"%>
- <!DOCTYPE html PUBLIC"-//W3C//DTD HTML 4.01 Transitional//EN"http://www.w3.org/TR/heml4/loose.dtd"><%@ taglib uri="/myTag" prefix="hello" %>
- <html>
- <head>
- </head>
- <body>
- <!-- key的值 傳到 標籤處理類的 setKey() -->
- <hello:message key="title"/><br/>
- <hello:message key="body"/>
- </body>
- </html>