1.创建MyTag类，并继承TagSupport类
增加key属性，并实现doEndTag方法
MyTag.java
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import java.util.Properties; import javax.servlet.jsp.JspException; import javax.servlet.jsp.PageContext; import javax.servlet.jsp.tagext.TagSupport; public class MyTag
extends TagSupport { private String key; public String getKey() { return key; } public void setKey(String key) { this.key = key; } @Override public int doEndTag() throws JspException { try { Properties p = (Properties)this.pageContext.getAttribute("p",PageContext.APPLICATION_SCOPE); String message = p.getProperty(key); this.pageContext.getOut().println(message); } catch (Exception e) { e.printStackTrace(); } return EVAL_PAGE; } } |
2.创建一个initServlet，把properties中的属性添加到Application范围中
把initServlet设为服务器启动即加载
Message.properties
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title=hello world body=welcome |
Web.xml
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<servlet> <servlet-name>InitServlet</servlet-name> <servlet-class>com.anllin.servlet.InitServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> |
InitServlet.java
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import java.io.InputStream; import java.util.Properties; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; public class InitServlet extends HttpServlet { @Override public void init(ServletConfig config) throws
ServletException { Properties p = new Properties(); try { ServletContext context =
config.getServletContext(); InputStream is =
context.getResourceAsStream("/WEB-INF/message.properties"); p.load(is); is.close(); //把properties放置到application范围内以供其他组件使用。 context.setAttribute("p",p); } catch (Exception e) { // TODO: handle exception } } } |
3.创建自己的标签库
myTag.tld
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<?xml version="1.0"
encoding="UTF-8"?> <!DOCTYPE
taglib PUBLIC "-//Sun Microsystems, Inc.//DTD
JSP Tag Library 1.2//EN" "http://java.sun.com/j2ee/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> <display-name>myTag</display-name> <tag> <name>firstTag</name> <tag-class>com.anllin.taglib.MyTag</tag-class> <body-content>empty</body-content> </tag> <tag> <name>message</name> <tag-class>com.anllin.taglib.MyTag</tag-class> <body-content>empty</body-content> <attribute> <name>key</name> <required>true</required> </attribute> </tag> </taglib> |
4.在jsp中使用标签库。
Tag.jsp
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<%@ page language="java"
import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib uri="/myTag"
prefix="hello" %> <!DOCTYPE HTML
PUBLIC "-//W3C//DTD
HTML 4.01 Transitional//EN"> <html> <head> <title>My JSP 'tag.jsp' starting page</title> </head> <body> <hello:message key="title"/><br> <hello:message key="body"/> </body> </html> |