java(18)--自定义标签调用

使用标签输出客户机IP。

1.先在web.xml文件中注册一个jsp-config

    <jsp-config>
        <taglib>
            <taglib-uri>http://zgq.com</taglib-uri>
            <taglib-location>/zgq.tld</taglib-location>
        </taglib>
    </jsp-config>

2.编写一个实现tag接口的java类

public class ViewIPTag extends TagSupport {

    @Override
    public int doStartTag() throws JspException {

        HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
        JspWriter out = this.pageContext.getOut();


        String ip = request.getRemoteAddr();
        try {
            out.print(ip);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        return super.doStartTag();
    }
}

3.在tld文件中对标签处理器类进行描述（tld文件的位置:WEB-INF下,可以抄C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\examples\WEB-INF\jsp2\jsp2-example-taglib.tld）

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd" version="2.0">

    <description>A tag library exercising SimpleTag handlers.</description>
    <tlib-version>1.0</tlib-version>
    <short-name>zgq</short-name>
    <uri>http://zgq.com</uri>


    <tag>
        <name>viewIP</name>
        <tag-class>zgq.web.tag.ViewIPTag</tag-class>
        <body-content>empty</body-content>
    </tag>

</taglib>

4.在jsp页面中导入和使用自定义标签

<%@taglib uri="http://zgq.com" prefix="zzz" %>
  <zzz:viewIP/>

下面是自定义标签调用流程