如何实现自定义标签
1、自定义一个用表格显示用户信息的简单标签
简单标签的开发我们只要实现Tag接口即可，为了简单起见可以直接继承实现了此接口的TagSupport类
2、创建自定义标签类
public class UserInfoTag extends TagSupport {
private UserInfo user;
@Override
public int doStartTag() throws JspException {
try {
JspWriter out = this.pageContext.getOut();
if(user == null) {
out.println("No UserInfo Found...");
return SKIP_BODY;
}
out.println("<table width='500px' border='1' align='center'>");
out.println("<tr>");
out.println("<td width='20%'>Username:</td>");
out.println("<td>" + user.getUserName() + "</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Age:</td>");
out.println("<td>" + user.getAge() + "</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Email:</td>");
out.println("<td>" + user.getEmail() + "</td>");
out.println("</tr>");
out.println("</table>");
} catch(Exception e) {
throw new JspException(e.getMessage());
}
return SKIP_BODY;
}
@Override
public int doEndTag() throws JspException {
return EVAL_PAGE;
}
@Override
public void release() {
super.release();
this.user = null;
}
//getter and setters
public UserInfo getUser() {
return user;
}
public void setUser(UserInfo user) {
this.user = user;
}
}
3、在Web-Inf创建标签库描述文件.tdl(Tag Library Description)
<?xml version="1.0" encoding="UTF-8"?>
<taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd">
<tlib-version>1.0</tlib-version>
<jsp-version>2.0</jsp-version>
<short-name>cc</short-name>
<uri>/mytaglib</uri>
<tag>
<name>showUserInfo</name>
<tag-class>com.mytags.UserInfoTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>user</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
4、配置web.xml
<jsp-config>
<taglib>
<taglib-uri>/mytaglib</taglib-uri>
<taglib-location>/WEB-INF/mytaglib.tld</taglib-location>
</taglib>
</jsp-config>
5、在需要使用此标签的jsp页面头部引入
<%@ taglib uri="/mytaglib" prefix="cc"%>
6、使用（参照上面的使用步骤）
此致，一个简单的JSP标签开发完成