一个类似于Logic与Bean的Jsp标签示例
示例说明:
首先通过Logic标准的校验,是否存在相应的属性,如果不存在,就不继续执行其中包含的内容体,如果存在则执行其中包含的内容体,调用方式如:
<mytest:logic>
<mytest:bean xpath="/Document/Element[@name=/"e2/"]">
</mytest:bean>
</mytest:logic>
这里有两个类,一个是MyLogic类,一个是MyBean,分别代表上面的logic及bean。
1、MyLogic源程序:
package test;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.jdom.Document;
public class MyLogic extends BodyTagSupport {
/**
*
*/
private static final long serialVersionUID = 1L;
public MyLogic(){
super();
}
public int doStartTag() throws JspException{
Object object=getDataElement(pageContext);
/*如果属性不存在,就不继续其中包含的内容体了*/
if(object==null){
System.out.println("xmlDoc属性不存在");
return SKIP_BODY;
}
System.out.println("xmlDoc属性存在");
//EVAL_BODY_INCLUDE表示继续执行内容体
return EVAL_BODY_INCLUDE;
}
/*根据属性取对Document对象*/
public Document getDataElement(PageContext pageContext) {
Document root =null;
try{
root= (Document) pageContext.getRequest().getAttribute("xmlDoc");
}catch(Exception e){
}
return root;
}
}
2、MyBean源程序:
package test;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.xpath.XPath;
public class MyBean extends BodyTagSupport{
/**
*
*/
private static final long serialVersionUID = 1L;
public MyBean(){
super();
}
String xpath;
public String getXpath() {
return xpath;
}
public void setXpath(String xpath) {
this.xpath = xpath;
}
public int doStartTag() throws JspException{
String thisXPath=getXpath();
System.out.println("传入的XPath:"+thisXPath);
Document xmlDoc=(Document) pageContext.getRequest().getAttribute("xmlDoc");
try {
String value=((Element)(XPath.selectSingleNode(xmlDoc, thisXPath))).getText();
/*输出根据XPath取的的值*/
pageContext.getOut().write(value);
/*如果该页面中其它地方不再使用该属性,记得删除,这是一个好习惯*/
pageContext.getRequest().removeAttribute("xmlDoc");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return super.doStartTag();
}
}
3、tld文件的名称为mytest.tld,将其放在/WEB-INF/tagtld/test目录下,其内容为:
<?xml version="1.0" encoding="GB2312"?>
<!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>1.0</jsp-version>
<short-name>mytest</short-name>
<uri>http://mytest.com</uri>
<display-name>这是我的测试标签</display-name>
<description>
测试标签
</description>
<tag>
<name>logic</name>
<tag-class>test.MyLogic</tag-class>
<description>
My Logic
</description>
</tag>
<tag>
<name>bean</name>
<tag-class>test.MyBean</tag-class>
<description>
My Bean
</description>
<attribute>
<name>xpath</name>
<required>true</required>
</attribute>
</tag>
</taglib>
4、web.xml中加入如下配置:
<taglib>
<taglib-uri>/WEB-INF/tagtld/test/mytest.tld</taglib-uri>
<taglib-location>
/WEB-INF/tagtld/test/mytest.tld
</taglib-location>
</taglib>
5、测试JSP页面:
<%@ taglib uri="/WEB-INF/tagtld/test/mytest.tld" prefix="mytest"%>
<%@ page import="org.jdom.*"%>
<%@ page import="util.JDomUtil"%>
<%
String xmlString="<?xml version=/"1.0/" encoding=/"gb2312/"?><Document><Element name=/"e1/">first</Element><Element name=/"e2/">second</Element></Document>";
Document xmlDoc=JDomUtil.getDocument(xmlString);
//你可以将下面这一句屏蔽看一下效果
request.setAttribute("xmlDoc", xmlDoc);
%>
<mytest:logic>
<mytest:bean xpath="/Document/Element[@name=/"e2/"]">
</mytest:bean>
</mytest:logic>
本文出自:冯立彬的博客