struts1中logic标签详解，尤其是判断空否的4个标签的区别-优快云博客

本文链接：https://blog.youkuaiyun.com/codejavamao/article/details/83526038

(1)empty标签
类名：org.apache.struts.taglib.logic.EmptyTag
标签体：bodycontent=JSP
引用logic:empty
属性 attribute:name,property,scope
功能：判断对象的值是否为空

(2)equal
类名：org.apache.struts.taglib.logic.EqualTag
标签体：bodycontent=JSP
引用logic:equal
属性 attribute:cookie,header,name,parameter,property,scope,value
功能：等于比较符

(3) forward
org.apache.struts.taglib.logic.ForwardTag
标签体：bodycontent=empty
引用logic:forward
属性 attribute:name
功能：页面导向，查找配置文件的全局forward

(4) greaterEqual
类名：org.apache.struts.taglib.logic.GreaterEqualTag
标签体：bodycontent=JSP
引用logic:greaterEqual
属性 attribute:cookie,header,name,parameter,property,scope,value
功能：大于等于比较符

(5)greaterThan
类名：org.apache.struts.taglib.logic.GreaterThanTag
标签体：bodycontent=JSP
引用logic:greaterThan
属性 attribute:cookie,header,name,parameter,property,scope,value
功能：大于比较符

(6) iterator
类名：org.apache.struts.taglib.logic.IterateTag
标签体：bodycontent=JSP
引用logic:iterator
属性 attribute:collection,id,indexId,length,name,offset,property,scope,type
功能：显示列表为collection的值（List ,ArrayList,HashMap等）

(7)lessEqual
类名org.apache.struts.taglib.logic.LessEqualTag
标签体：bodycontent=JSP
logic:lessEqual
属性 attribute:cookie,header,name,parameter,property,scope,value
功能：小于等于比较符

(8)lessThan
类名：org.apache.struts.taglib.logic.LessThanTag
标签体：bodycontent=JSP
logic:lessThan
属性 attribute:cookie,header,name,parameter,property,scope,value
功能：小于比较符

(9)match
类名：org.apache.struts.taglib.logic.MatchTag
标签体：bodycontent=JSP
引用logic:match
属性 attribute:cookie,header,location,name,parameter,property,scope,value
功能：比较对象

(10)messagesNotPresent
类名：org.apache.struts.taglib.logic.MessagesNotPresentTag
标签：bodycontent=JSP
引用logic:messagesNotPresent
属性 attribute:name,property,message
功能：ActionMessages/ActionErrors对象是否不存在

(11)messagePresent
类名：org.apache.struts.taglib.logic.MessagesPresentTag
标签：bodycontent=JSP
引用logic:messagePresent
属性 attribute:name,property,message
功能：ActionMessages/ActionErrors对象是否不存在

(12)notEmpty
类名：org.apache.struts.taglib.logic.NotEmptyTag
标签：bodycontent=JSP
引用logic:notEmpty
属性 attribute:name,property,scope
功能：比较对象是否不为空

(13)notEqual
类名：org.apache.struts.taglib.logic.NotEqualTag
标签：bodycontent=JSP
引用logic:notEqual
属性 attribute:cookie,header,name,parameter,property,scope,value

(14)notMatch
类名：org.apache.struts.taglib.logic.NotMatchTag
标签：bodycontent=JSP
引用logic:notMatch
属性 attribute:cookie,header,location,name,parameter,property,scope,value
功能：比较对象是否不相等

(15)notPresent
类名：org.apache.struts.taglib.logic.NotPresentTag
标签：bodycontent=JSP
引用logic:notPresent
属性 attribute:cookie,header,name,parameter,property,role,scope,user
功能：request对象传递参数是否不存在

(16)present
类名:org.apache.struts.taglib.logic.PresentTag
标签：bodycontent=JSP
引用logic:present
属性 attribute:cookie,header,name,parameter,property,role,scope,user
功能：request对象传递参数是否存在

(17)redirect
类名：org.apache.struts.taglib.logic.RedirectTag
标签：bodycontent=JSP
引用logic:redirect
属性 attribute:anchor,forward,href,name,page,paramId,paramName,paramProperty,paramScope,property,scope,transaction
功能；页面转向，可传递参数

例子：

1、<logic:iterate id="row" name="formBean" property="list" indexId="index">
<logic:equal name="row" property="unit" value="defaultValue">
...
</logic:equal>
</logic:iterate>

<logic:notEmpty name="info">
<logic:iterate id="list" name="info">
          <bean:define id="curId" name="list" property="id" />
          <logic:equal parameter="id" value="<%= curId.toString() %>">
                abcde
</logic:equal>
</logic:iterate>
</logic:notEmpty>
parameter要进行比较的HTTP请求参数的名称
name如果要进行比较的是bean或bean的属性，则这个属性代表bean的名称
property要进行比较的bean属性的名称

logic使用

使用struts中的<logic:iterate>标记,可以完成一些复杂的循环。
下面用了一个小例子说明这一点：

IterateBean.java:

package beantest;

import org.apache.struts.action.ActionForm;

public class IterateBean extends ActionForm {
private String[] name_coll = null;
public void setName_coll(String[] name_coll) {
this.name_coll = name_coll;
}
public String[] getName_coll() {
return this.name_coll;
}

private String[] name_new = null;
public void setName_new(String[] name_new) {
System.out.println("IterateBean:setName_new(String[])");
this.name_new = name_new;
}
public String[] getName_new() {
return this.name_new;
}
}

IterateAction.java

package beantest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

public class IterateAction extends Action {
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws Exception {
IterateBean ibean = (IterateBean) form;
String[] temp = {"bitan", "helen"};
ibean.setName_coll(temp);
temp = new String[] {"aaaaa", "bbbbb"};
ibean.setName_new(temp);
return mapping.findForward("iterate-view");
}
}

iterate-view.jsp:

<%@ page contentType="text/html;charset=gb2312" %>

<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<logic:iterate id="iterate" name="ibean" property="name_coll" scope="request" offset="0" >

<logic:iterate id="iterate_new" name="ibean" property="name_new" scope="request" offset="0" >
name: <font color=red><%=iterate%></font> ; code: <font color=red><%=iterate_new%></font><br>
</logic:iterate>

★〓〓〓〓〓〓〓〓★<br>
<bean:include id="lower" page="/test/lower.jsp" />
<bean:write name="lower" filter="false"/><br>
</logic:iterate>

lower.jsp:

<font color=blue>hello, iterate!</font>

struts-config.xml:

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
"http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">
<struts-config>
<form-beans>
<form-bean type="beantest.IterateBean" name="ibean" />
</form-beans>
<action-mappings>
<action path="/iterate-test" type="beantest.IterateAction" name="ibean" scope="request" >
<forward path="/test/iterate-view.jsp" name="iterate-view" />
</action>
</action-mappings>
</struts-config>

web.xml:

<?xml version="1.0" ?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>

<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>/eye/*</url-pattern>
</servlet-mapping>

</web-app>

输出效果：

name: bitan ; code: aaaaa
name: bitan ; code: bbbbb
★〓〓〓〓〓〓〓〓★
hello, iterate!
name: helen ; code: aaaaa
name: helen ; code: bbbbb
★〓〓〓〓〓〓〓〓★
hello, iterate!

如上所示，一个循环中不能直接将多个变量同时输出；但在循环中嵌套循环可以实现一种复杂效果。

要实现在一个循环中将多个变量同时输出，可以引用<bean:include>、<bean:write>标记。