Html:options是Struts中比较复杂的一个tage lib,用法灵活,但是Sturts提供的源码exercise taglib中没有提出常用jsp+ActionForm这样形式的最直接的总结,现从中总结如下,分两种情况:数组和Collection。
需求,要达到:
<select name="beanCollectionSelect" multiple="multiple" size="10"><option value="Value 0">Label 0</option><option value="Value 1" selected="selected">Label 1</option><option value="Value 2">Label 2</option><option value="Value 3" selected="selected">Label 3</option><option value="Value 4">Label 4</option><option value="Value 5" selected="selected">Label 5</option><option value="Value 6">Label 6</option><option value="Value 7">Label 7</option><option value="Value 8">Label 8</option><option value="Value 9">Label 9</option></select>
要实现上述效果,需要两步:
第一:设置ActionForm,
也分两小步:第一小步必须在ActionForm中,有一句
private Collection beanCollection;
public Collection getBeanCollection();
Collection beanCollection要确保是一个实现,如ArrayList,假如不是则会报No collection found的错误,Struts的最大不方便就是一旦出问题,定位很难,不知道什么地方使用错误,或忘记设置什么了。
因为前面需求中option的value值和label值不一样,那么在beanCollection中保存的就是一个value和label组成的对象,名为LabelValueBean,在LabelValueBean中有两个属性value和label,
在程序某个地方要为beanCollection赋值,如:
Vector entries = new Vector(10); entries.add(new LabelValueBean("Label 0", "Value 0")); entries.add(new LabelValueBean("Label 1", "Value 1")); entries.add(new LabelValueBean("Label 2", "Value 2")); entries.add(new LabelValueBean("Label 3", "Value 3")); entries.add(new LabelValueBean("Label 4", "Value 4")); entries.add(new LabelValueBean("Label 5", "Value 5")); entries.add(new LabelValueBean("Label 6", "Value 6")); entries.add(new LabelValueBean("Label 7", "Value 7")); entries.add(new LabelValueBean("Label 8", "Value 8")); entries.add(new LabelValueBean("Label 9", "Value 9"));
然后执行setBeanCollection(entries);
这样ActionForm中的beanCollection算有值了。
第二小步,需要设置Selected,selected有两种,单选和多选:
在ActionForm中必须有:
private String singleSelect = "Single 5"; public String getSingleSelect() { return (this.singleSelect); } public void setSingleSelect(String singleSelect) { this.singleSelect = singleSelect; }
或多选,多选必须是数组:
private String[] beanCollectionSelect = { "Value 1", "Value 3", "Value 5" }; public String[] getBeanCollectionSelect() { return (this.beanCollectionSelect); } public void setBeanCollectionSelect(String beanCollectionSelect[]) { this.beanCollectionSelect = beanCollectionSelect; }
第二:在Jsp中写入tang lib语句如下:
<html:select property="beanCollectionSelect" size="10" multiple="true"> <html:optionsCollection name="testbean" property="beanCollection"/> </html:select>
其中testbean是ActionForm的名称。
以上是html:options的Collection解决方案,假如option值很少,简单地可以实现为数组,两步:
第一:在ActionForm中,
private String values[] = { "Magazine", "Journal", "News Paper","Other" }; private String labels[] = { "L-Magazine", "L-Journal", "L-News Paper","L-Other"}; private String selected = "Magazine"; public String getSelected(){ return selected; } public void setSelected(String selected){ this.selected = selected; } public String[] getValues(){ return values; } public void setValues(String[] values){ this.values = values; } public String[] getLabels(){ return values; } public void setLabels(String[] labels){ this.labels = labels; }
第二步在jsp中:
<html:select property="selected" > <html:options name="testbean" property="values" labelProperty="label"/> </html:select>