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doubleselect的用法示例

在Struts2的官方网站上，有doubleselect的用法示例，但是那个例子比较简单。<s:doubleselect label="doubleselect test2" name="menu" list="#{'fruit':'Nice Fruits', 'other':'Other Dishes'}" doubleName="dishes" doubleList="top == 'fruit' ? {'apple', 'orange'} : {'monkey', 'chicken'}" />

 

设置样式,使之不换行:

<style>

    .nobr br{display:none}   </style>

<div class="nobr">

     <s:doubleselect label="doubleselecttest2" name="menu" list="#{'fruit':'Nice Fruits', 'other':'Other Dishes'}" doubleName="dishes" doubleList="#top=='fruit'?{'apple', 'orange'}:{'monkey', 'chicken'}" theme="simple"/> </div>

上面的例子演示了doubleselect的基本用法，但是其list和doubleList都是固定的。尤其是doublelist的切换使用了3目运算符 ? :，并没有太大的实际使用价值。在实际应用中，list往往是action返回的一个List<DataObject>，listKey和listValue来显示第一级下拉框，doubleList往往是一个Map<Integer, List<DataObject>>，其中Map中的Key值是第一级下拉框的listKey。举个例子：Data Object:public class Book {         private int id;        private String name;        private int categoryId;

        // getter and setter..

}

public class Category {

        private int id;        private String name;

        // getter and setter..

}

JSP:

<s:doubleselect list="categoryList" listKey="id" listValue="name"    doubleName="bookId" doubleList="bookMap.get(top.id)" doubleListKey="id" doubleListValue="name" theme="simple"/>

此处要注意的是top的用法，开始我以为top就是指代list的值，所以使用的是bookMap.get(top)，但是二级下拉框一直是空白，后来我突然想到说不定top是一个Category实例呢，尝试了一下top.id，果然成功了。

Action:

public class DemoAction {

        private Map<Integer, List<Book>> bookMap;        private List<Category> categoryList;

        public String execute() throws Exception {

                categoryList = new ArrayList<Cateogry>();

                Category category;

                category = new Category();                category.setId(1);                category.setName("Fiction");                categoryList.add(category);                category = new Category();                category.setId(2);                category.setName("Java");                categoryList.add(category);

 

                bookMap = new HashMap<Integer, List<Book>>();

                List<Book> bookList = new ArrayList<Book>();

                Book book;                book = new Book();                book.setId(1);                book.setName("Harry Porter");                book.setCategoryId(1);                bookList.add(book);

                book = new Book();

                book.setId(2);                book.setName("Nightmare");                book.setCategoryId(1);                bookList.add(book);

                bookMap.put(1, bookList);

 

                bookList = new ArrayList<Book>();

                book = new Book();                book.setId(3);                book.setName("Thinking in Java");                book.setCategoryId(2);                bookList.add(book);                book = new Book();                book.setId(4);                book.setName("Head First Design Patterns");                book.setCategoryId(2);                bookList.add(book);

                bookMap.put(2, bookList);

                return SUCCESS;        }

        // getter and setter..

}

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