条件 Thymeleaf 片段

Question

我想使用模板片段创建最多包含三个项目的列表。无论是否有项目，都会显示三个项目空格，所以看起来像这样。

<div>
  <div th:if="${#lists.size(block.children) > 0}"
    th:insert="code-block :: block(${block.children[0]})" 
    th:remove="tag">
  </div>
</div>;
<div>
  <div th:if="${#lists.size(block.children) > 1}"
    th:insert="code-block :: block(${block.children[1]})" 
    th:remove="tag">
  </div>
</div>;
<div>
  <div th:if="${#lists.size(block.children) > 2}"
    th:insert="code-block :: block(${block.children[2]})" 
    th:remove="tag">
  </div>
</div>

但是，即使该th:if语句在空列表中评估为 false，它仍然尝试执行 `th:include 语句，给出以下错误：

Caused by: org.springframework.expression.spel.SpelEvaluationException:
EL1025E:(pos 14): The collection has '0' elements, index '0' is invalid

如何使 if 语句优先于片段执行？

Answer 1

是的，不幸的是，由于include优先级高于if，因此您将不得不向上移动if。最简单的方法是将其放入 a 中th:block，如下所示：

<div>
  <th:block th:if="${#lists.size(block.children) > 0}">
    <div th:insert="code-block :: block(${block.children[0]})" th:remove="tag" />
  </th:block>
</div>;
<div>
  <th:block th:if="${#lists.size(block.children) > 1}">
    <div th:insert="code-block :: block(${block.children[1]})" th:remove="tag" />
  </th:block>
</div>;
<div>
  <th:block th:if="${#lists.size(block.children) > 2}">
    <div th:insert="code-block :: block(${block.children[2]})" th:remove="tag" />
  </th:block>
</div>

您还可以简化您的代码，使其看起来更像这样：

<th:block th:each="i: ${#numbers.sequence(0, 2)}">
  <th:block th:if="${#lists.size(block.children) > i}">
    <div th:insert="code-block :: block(${block.children[i]})" th:remove="tag" />
  </th:block>

  <th:block th:unless="${i == 2}">;</th:block>
</th:block>