Struts标签库

      在JSP页面中，使用标记库代替传统的Java代码来实现页面的显示逻辑是大势所趋，然而，由于自定义标记很容易造成重复定义和非标准的实现，于是出现了基于java Web的JSTL和基于struts的taglib等标签库来解决这些问题。

   这些标签库在实现原理上相差无几，学会一种，另一种也就很容易上手，那咱们就从Struts的标签库走起。

   常用的strust标签库有<bean:write>、<logic:empty>和<logic:notEmpty>、<logic:present>和<logic:notPresent>、<logic:iterator>4种。

   使用方法：

   1.在strus-config.xml中配置message-resources，注意，这个标签要放在action-mappings标签后面。配置信息如下：

<message-resources parameter="MessageResources" />

   3.在JSP页面中引入taglib

<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> 
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%>

   (1)<bean:wriete>-->action

public class BeanWriteAction extends Action {

	@Override
	public ActionForward execute(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		// 普通字符串
		request.setAttribute("hello", "quwenzhe");
		request.setAttribute("today", new Date());

		Group group = new Group();
		group.setName("提高班");

		User user = new User();
		user.setUsername("quwenzhe");
		user.setAge("24");
		user.setGroup(group);

		request.setAttribute("user", user);

		return mapping.findForward("success");
	}
}

姓名：<input type="text" name="username" value="<bean:write name="user" property="username"/>"><br/>
年龄：<input type="text" name="age" value="	<bean:write name="user" property="age"/>"><br>
所属组:<input type="text" name="group" value="	<bean:write name="user" property="group.name"/>"><br/>

public class EmptyPresentAction extends Action {

	@Override
	public ActionForward execute(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		request.setAttribute("attr1", null);
		request.setAttribute("attr2", "");
		request.setAttribute("attr3", new ArrayList());

		return mapping.findForward("success");
	}
}

              <logic:empty>和<logic:notEmpty>、<logic:present>和<logic:notPresent>-->JSP

		<p>
		<logic:empty name="attr1">
			attr1为空
		</logic:empty>
		<logic:notEmpty name="attr1">
			attr1为空
		</logic:notEmpty>
		<logic:present name="attr1">
			attr1存在
		</logic:present>
		<logic:notPresent name="attr1">
			attr1不存在
		</logic:notPresent>
		</p>
		
		<p>
		<logic:empty name="attr2">
			attr2为空
		</logic:empty>
		<logic:notEmpty name="attr2">
			attr2为空
		</logic:notEmpty>
		<logic:present name="attr2">
			attr2存在
		</logic:present>
		<logic:notPresent name="attr2">
			attr2不存在
		</logic:notPresent>
		</p>
		
		<p>
		<logic:empty name="attr3">
			attr3为空
		</logic:empty>
		<logic:notEmpty name="attr3">
			attr3为空
		</logic:notEmpty>
		<logic:present name="attr3">
			attr3存在
		</logic:present>
		<logic:notPresent name="attr3">
			attr3不存在
		</logic:notPresent>
		</p>

public class IteratorAction extends Action {

	@Override
	public ActionForward execute(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		Group group = new Group();
		group.setName("提高班");

		List userList = new ArrayList();

		for (int i = 0; i < 10; i++) {
			User user = new User();
			user.setUsername("quwenzhe-->" + i);
			user.setAge("24-->" + i);
			user.setGroup(group);

			userList.add(user);
		}
		request.setAttribute("userList", userList);
		return mapping.findForward("success");
	}
}

              <logic:iterator>-->JSP

		<table border="1">
			<tr>
				<td>姓名</td>
				<td>年龄</td>
				<td>所属组</td>
			</tr>
			<logic:empty name="userList">
				<tr>
					<td colspan="3">没有符合条件的数据</td>
				</tr>
			</logic:empty>
			<logic:notEmpty name="userList">
				<logic:iterate id="user" name="userList">
					<tr>
						<td>
							<bean:write name="user" property="username"/>
						</td>
						<td>
							<bean:write name="user" property="age"/>
						</td>
						<td>
							<bean:write name="user" property="group.name"/>
						</td>
					</tr>
				</logic:iterate>
			</logic:notEmpty>
		</table>

        这样我们在后台Action中通过request设置的值，在JSP页面中通过标签就能很方便的获取到，大大提高工作效率。

Struts标签库

原文：http://blog.csdn.net/quwenzhe/article/details/39483053