英文:
Handling Integers as Strings in Thymeleaf Arrays and Lists
问题
为什么以下 Thymeleaf 的 th:if 测试对字符串 "0"、"1" 和 "9" 失败？
我有一个 Java 数组如下：
String[] arrayData = {"x", "-1", "0", "1", "9", "10", "11"};
其中包括 "x" 是为了说明该数组既可以包含字母值，也可以包含数字值。
我有一个包含以下内容的 Thymeleaf 模板：
<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Test</title>
<meta charset="UTF-8">
</head>
<body>
<div th:if="${#arrays.contains(arrayData, '-1')}"
th:text="'found array string ''-1'''"></div>
<div th:if="${#arrays.contains(arrayData, '0')}"
th:text="'found array string ''0'''"></div>
<div th:if="${#arrays.contains(arrayData, '1')}"
th:text="'found array string ''1'''"></div>
<div th:if="${#arrays.contains(arrayData, '9')}"
th:text="'found array string ''9'''"></div>
<div th:if="${#arrays.contains(arrayData, '10')}"
th:text="'found array string ''10'''"></div>
<div th:if="${#arrays.contains(arrayData, '11')}"
th:text="'found array string ''11'''"></div>
</body>
</html>
我期望这会在浏览器中生成以下输出：
found array string '-1'
found array string '0'
found array string '1'
found array string '9'
found array string '10'
found array string '11'
但实际上我得到了以下结果：
found array string '-1'
found array string '10'
found array string '11'
问题：为什么对于字符串 "0"、"1" 和 "9" 的测试会失败？我做错了什么？
所有针对字符串值 "0" 到 "9" 的测试都失败。在该范围之外的任何值都按预期工作。
如果我使用 ArrayList<String> 并使用 Thymeleaf 的 #lists.contains() 操作符，情况也是一样的。
Thymeleaf 版本是：
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf</artifactId>
<version>3.0.11.RELEASE</version>
</dependency>
据我所知，实现 #arrays.contains() 函数的 Thymeleaf 代码在这里 - 它看起来很简单。
我的 Java 版本是 AdoptOpenJDK 14。
在这个特定场景中，我没有使用 Spring。
回答后更新
如果我测试任何单个字符（例如 x），与 "0" 到 "9" 一样会出现相同的问题。所以标题在这方面有些误导。
英文:
Why do the following Thymeleaf th:if tests fail for the strings "0", "1", and "9"?
I have a Java array as follows:
String[] arrayData = {"x", "-1", "0", "1", "9", "10", "11"};
The "x" is included to clarify that this array can contain alphabetic values as well as numeric values.
I have a Thymeleaf template containing the following:
<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Test</title>
<meta charset="UTF-8">
</head>
<body>
<div th:if="${#arrays.contains(arrayData, '-1')}"
th:text="'found array string \'-1\''"></div>
<div th:if="${#arrays.contains(arrayData, '0')}"
th:text="'found array string \'0\''"></div>
<div th:if="${#arrays.contains(arrayData, '1')}"
th:text="'found array string \'1\''"></div>
<div th:if="${#arrays.contains(arrayData, '9')}"
th:text="'found array string \'9\''"></div>
<div th:if="${#arrays.contains(arrayData, '10')}"
th:text="'found array string \'10\''"></div>
<div th:if="${#arrays.contains(arrayData, '11')}"
th:text="'found array string \'11\''"></div>
</body>
</html>
I expect this to generate the following output in a browser:
found array string '-1'
found array string '0'
found array string '1'
found array string '9'
found array string '10'
found array string '11'
But I actually get the following:
found array string '-1'
found array string '10'
found array string '11'
Question: Why do the tests fail for the strings "0", "1", and "9"? What am I doing wrong?
All such tests for the ten string values "0" through "9" fail. Anything outside that range works as expected.
The same thing happens if I use an ArrayList<String>, with the Thymeleaf #lists.contains() operator.
The Thymeleaf version is:
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf</artifactId>
<version>3.0.11.RELEASE</version>
</dependency>
As far as I can tell, I think the Thymeleaf code which implements the #arrays.contains() function is here - and it looks straightforward.
My Java version is AdoptOpenJDK 14.
I am not using Spring in this specific scenario.
Update, After Answer was Provided
If I test with any single character (e.g. x) the same problem happens as with 0 through 9. So the title is somewhat misleading in that regard.
答案1
得分: 2
我怀疑如果你没有使用Spring，Thymeleaf表达式将会使用OGNL来解释，而不是SPeL —— 这似乎将单个字符常量视为char类型而不是String类型，因此#arrays.contains表达式无法匹配。
我没有设置来测试OGNL，但根据这篇帖子，这应该可以工作：
<div th:text="${#arrays.contains(arrayData, "0")}" />
（或者也许#arrays.contains(arrayData, '' + '0')会起作用？）
英文:
I suspect that if you aren't using Spring, Thymeleaf expressions are being interpreted using OGNL insteald of SPeL -- which appears to treat single character constants as type char instead of type String and so the #arrays.contains expressions fail to match.
I don't have a setup to test OGNL, but according to this post, this should work:
<div th:text="${#arrays.contains(arrayData, &quot;0&quot;)}" />
(Or maybe #arrays.contains(arrayData, '' + '0') would work?)
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