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s:iterator usage and examples

高洛峰

Release： 2016-12-13 17:29:45

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s: Iterator attribute introduction

s:iterator usage and examples

*IneratorStatus object introduction:

This type of object encapsulates the relevant information of this cycle, which is obtained by accessing its attributes. The main attributes are:

　 Index: The current loop to Index of the collection

　 Count: The number of times it has been cycled

　 First: Whether it is the first cycle

　 Last: Whether it is the last cycle

　odd: Whether the current position is an odd number

Even: whether the current position is an even number

eg:

Create a new class Action1.java, the code is as follows:

package my.test;

import com.opensymphony.xwork2.ActionSupport;

public class Action1 extends ActionSupport{
    private String[] arr=new String[5];
    
    //一定要添加get/set方法，否则会出现空指针异常
    public String[] getArr() {
        return arr;
    }

    public void setArr(String[] arr) {
        this.arr = arr;
    }

    public String execute(){
        int i=101;
        //下面的for循环的赋值不起作用
        for(String a:arr){
            a=""+i++;
        }
        arr[3]="this is 3";//这里验证上面的for循环对arr的赋值是不起作用的，这里由String数组和String的特性来决定，看运行结果即可
        return SUCCESS;
    }
}

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Create a new jsp file/iterator.jsp, remember to introduce the Struts tag

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <s:debug></s:debug>
    <s:iterator var="one" value="arr" begin="2" status="sta">
        <!-- 由于循环到的值保存到值栈中，所以下面通过s:property标签取值 -->
        循环到的值为：<s:property value="one"/><br>
        循环的次数为：<s:property value="#sta.count"/><br>
        循环的索引为：<s:property value="#sta.index"/><br>
        是否为奇数：<s:property value="#sta.odd"/><hr>
    </s:iterator>
</body>
</html>

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The last configuration file is:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

    <constant name="struts.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="true" />
    
    <package name="test" namespace="/" extends="struts-default">
        <action name="iterator" class="my.test.Action1">
            <result>/iterator.jsp</result>
        </action>
        <action name="index">
            <result type="redirectAction">
                <param name="actionName">HelloWorld</param>
                <param name="namespace">/example</param>
            </result>
        </action>
    </package>

    <!-- Add packages here -->

</struts>

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The author is using Struts2 version 2.3.30 , the configuration files of different versions are different.

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s:iterator 的属性