doubleselect用法 展示不换行

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..
}