Biegral Blog

JSP自定义标签的定义步骤：

1、创建标记处理器

2、创建TLD文件

3、编辑web.xml

4、在JSP页面中使用JSP自定义标签

在jsp页面使用自定义标签：

假设我们有一个UserInfo的javabean，那么在JSP页面使用此标签只需调用此标签即可

<!-- 创建需要展现UserInfo的实例（用于测试数据） -->

<%

    UserInfo user = new UserInfo();

    user.setUserName("Xuwei");

    user.setAge(33);

    user.setEmail("test@test.test");

    pageContext.setAttribute("userinfo", user);  

    %>

    <!-- 给标签设置user属性绑定要展现的UserInfo对象  -->

    <cc:showUserInfo user="${pageScope.userinfo }" />

开发步骤：

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

1 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;

    }

} 

<?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>

 

<jsp-config>

    <taglib>

        <taglib-uri>/mytaglib</taglib-uri>

        <taglib-location>/WEB-INF/mytaglib.tld</taglib-location>

    </taglib>

  </jsp-config> 

<%@ taglib uri="/mytaglib" prefix="cc"%>