java 对 Thymeleaf 中的实体使用“选择”标签
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Using 'select' tag with entities in Thymeleaf
提问by Filip Spiridonov
I am creating a form with the select tag that looks like this:
我正在创建一个带有 select 标签的表单，如下所示：
<form th:object="${version}" method="post" class="form-horizontal">
...
<div class="control-group" th:classappend="${#fields.hasErrors('product')} ? 'error'">
<label class="control-label" for="product" th:text="#{version.product}">Product</label>
<div class="controls">
<select id="product" th:field="*{product}">
<option value="" th:text="#{common.select.prompt}"></option>
<option th:each="p : ${productList}" th:value="${p.id}" th:text="${p.name}"></option>
</select>
<span class="help-inline" th:errors="*{product}"></span>
</div>
</div>
...
</form>
DomainClassConverterclass of Spring Data JPAhelps to auto-convert selected idto the entity Productwhen I submit the form. The productshould also be not null (I am using @NotNullon the productfield in the Versionclass.
DomainClassConverterclass ofSpring Data JPA有助于在我提交表单时将选定的自动转换id为实体Product。该product也应该是不为空（我用@NotNull的product领域Version类。
The problem that I have - when I come back to edit the data, the Productis not selected.
我遇到的问题 - 当我回来编辑数据时，Product没有选择。
If I modify the selectlike this (th:fieldand th:errors): <-- p.s. is not a sad smile
如果我select像这样修改（th:field和th:errors）：<-- p.s. is not a sad smile
<select id="product" th:field="*{product.id}">
<option value="" th:text="#{common.select.prompt}"></option>
<option th:each="p : ${productList}" th:value="${p.id}" th:text="${p.name}"></option>
</select>
<span class="help-inline" th:errors="*{product.id}"></span>
then it becomes selected when I come back to edit it, but the validator doesn't work (productis always instantiated, even if selected id is null).
然后当我回来编辑它时它会被选中，但是验证器不起作用（product总是被实例化，即使选择的 id 是null）。
It looks like a very common scenario (selecting an entity from the list), but I cannot find any good looking example. Please share the secret knowledge.
它看起来像一个非常常见的场景（从列表中选择一个实体），但我找不到任何好看的例子。请分享秘密知识。
采纳答案by Filip Spiridonov
Solved. The problem existed because I had not overridden the equals()and hashCode()methods.
解决了。问题存在是因为我没有覆盖equals()和hashCode()方法。
