java 带有空白默认值的 JSP 下拉列表
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JSP Dropdown List with Blank Default
提问by EdgeCase
I have a JSP Dropdown that is populated from a database query, and it is working just fine.
我有一个从数据库查询填充的 JSP Dropdown，它工作得很好。
But I want to also add a blank default option so that the field is empty when submitted. Right now the default is the first value selected from the database. But I want it to appear empty.
但我还想添加一个空白的默认选项，以便提交时该字段为空。现在默认值是从数据库中选择的第一个值。但我希望它看起来是空的。
The only way I've gotten it to work is to manually add a ""to the list as it is being populated.
我让它工作的唯一方法""是在填充列表时手动将其添加到列表中。
Is there a more elegant way of doing that?
有没有更优雅的方式来做到这一点？
<div class="row">
<label class="span2">Action</label>
<form:select path="Action">
<form:options items="${actionList}" />
<form:errors path="Action" cssClass="error"/>
</form:select>
</div>
Page with default values, which I do not want to appear by default:
带有默认值的页面，我不想默认显示：
回答by Andrea Ligios
Use single option element
使用单个选项元素
<form:select path="Action" >
<form:option value="" />
<form:options items="${actionList}" />
<form:errors path="Action" cssClass="error"/>
</form:select>
回答by Grim
An empty default is no good UI-Design. You should give a hint what to do.
空的默认值不是好的 UI 设计。你应该给一个提示该怎么做。
<div class="row">
<label class="span2">Action</label>
<form:select path="Action">
<option selected="selected"> -- Please choose --</option>
<form:options items="${actionList}" />
<form:errors path="Action" cssClass="error"/>
</form:select>
</div>
Or better html is
或者更好的 html 是
<div class="row">
<label class="span2">Action
<form:select path="Action">
<option selected="selected"> -- Please choose --</option>
<form:options items="${actionList}" />
<form:errors path="Action" cssClass="error"/>
</form:select>
</label>
</div>
If you like to style it like a table, you should remove the div, style the label as display:table-cell and ...
如果您喜欢将其样式设置为表格，则应删除 div，将标签样式设置为 display:table-cell 和 ...
回答by munkiepus
As the first answer is not particularly UX friendly and the second answer is not very spring-y :/
由于第一个答案对用户体验不是特别友好，而第二个答案不是很有弹性：/
Combining both the previous answers would give best of both worlds:
结合前面的两个答案将两全其美：
<form:select path="Action" >
<form:option value="">--Select one--</form:option>
<form:options items="${actionList}" />
<form:errors path="Action" cssClass="error"/>
</form:select>
and this will store a null value in the database.
这将在数据库中存储一个空值。
