此标签和sun公司的一样可以迭代Map,List,数组
jsp文件为
<%@page import="java.util.*"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="/simple" prefix="c"%>
<!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>foreach tag</title>
</head>
<body>
<%
List list = new ArrayList();
list.add("aaa");
list.add("bbb");
list.add("ccc");
request.setAttribute("list", list);
%>
<c:foreach var="str" items="${list}">
${str }
</c:foreach>
<br>------------------------------<br>
<%
Map map = new HashMap();
map.put("aa", "111");
map.put("bb", "222");
map.put("aa", "333");
request.setAttribute("map", map);
%>
<c:foreach var="entry" items="${map }">
${entry.key } = ${entry.value }
</c:foreach>
<br>------------------------------<br>
<%
Integer num[] = {1,2,3,4};
request.setAttribute("num", num);
%>
<c:foreach var="i" items="${num }">
${i }
</c:foreach>
<br>------------------------------<br>
<%
int arr[] = {1,2,3,4};
request.setAttribute("arr", arr);
%>
<c:foreach var="i" items="${arr }">
${i }
</c:foreach>
</body>
</html>package cn.itcast.web.tag;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
//开发foreach标签
public class ForeachTag extends SimpleTagSupport {
private Object items;
private String var;
//单列或双列集合存储至此
private Collection collection;
public void setItems(Object items) {
this.items = items;
//将map转为单列集合
if(items instanceof Map){
Map map = (Map) items;
collection = map.entrySet();
}
if(items instanceof Collection){
collection = (List) items;
}
//统一对数组进行处理
if(items.getClass().isArray()){
this.collection = new ArrayList();
int length = Array.getLength(items);
for(int i=0; i<length; i++){
Object value = Array.get(items, i);
collection.add(value);
}
}
/*if(items instanceof Object[]){
Object[] obj = (Object[]) items;
collection = Arrays.asList(obj); //此方法接受一个对象
}*/
}
public void setVar(String var) {
this.var = var;
}
@Override
public void doTag() throws JspException, IOException {
Iterator it = collection.iterator();
while(it.hasNext()){
Object obj = it.next();
//对象存在域中
this.getJspContext().setAttribute(var, obj);
//标签执行
this.getJspBody().invoke(null);
}
}
}
要记得在tld中对标签描述
<tag>
<name>foreach</name>
<tag-class>cn.itcast.web.tag.ForeachTag</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
