java Spring Boot SpEL ConditionalOnExpression 检查多个属性
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Spring Boot SpEL ConditionalOnExpression check multiple properties
提问by anataliocs
Question:
问题：
How can I use Spring Expression Language to check that 2 Boolean properties are true?
如何使用 Spring 表达式语言检查 2 个布尔属性是否为真？
For example, checking that a single property is true would use the syntax:
例如，检查单个属性是否为真将使用以下语法：
Example
例子
@ConditionalOnExpression("${property.from.properties.file}")
What would be the syntax for checking property1 == true && property2 == false? Where the properties can potentially have different values.
检查的语法是property1 == true && property2 == false什么？属性可能具有不同值的地方。
The answer from a similar question: How to check two condition while using @ConditionalOnProperty or @ConditionalOnExpressionconcatenates two strings together and performs a check like so:
来自类似问题的答案：如何在使用 @ConditionalOnProperty 或 @ConditionalOnExpression 时检查两个条件将两个字符串连接在一起并执行如下检查：
Concatenation Solution
串联方案
@ConditionalOnExpression("'${com.property1}${com.property2}'=='value1value2'")
That syntax seems confusing to someone reading that code and it seems like a hacky solution. There are some edge cases where the solution fails as well. I want to find the proper way to check two separate properties without concatenating the values.
对于阅读该代码的人来说，这种语法似乎令人困惑，而且它似乎是一个笨拙的解决方案。在某些边缘情况下，解决方案也会失败。我想找到在不连接值的情况下检查两个单独属性的正确方法。
Note:Also just to be clear, the answer isn't something you can easily search for from what I've seen. It seems like it would be a really simple answer but it's proving to be fairly elusive.
注意：同样要明确的是，答案不是您可以根据我所看到的轻松搜索的内容。这似乎是一个非常简单的答案，但事实证明它相当难以捉摸。
回答by anataliocs
The annotations @ConditionalOnPropertyand @ConditionalOnExpressionboth do NOT have the java.lang.annotation.Repeatableannotation so you would not be able to just add multiple annotations for checking multiple properties.
注释@ConditionalOnProperty和@ConditionalOnExpression两者都没有java.lang.annotation.Repeatable注释，因此您无法仅添加多个注释来检查多个属性。
The following syntax has been tested and works:
以下语法已经过测试并且有效：
Solution for Two Properties
两个属性的解决方案
@ConditionalOnExpression("${properties.first.property.enable:true} && ${properties.second.property.startServer:false}")
Note the following:
请注意以下事项：
- You need to using colon notation to indicate the default value of the property in the expression language statement
- Each property is in a separate expression language block ${}
- The && operator is used outside of the SpEL blocks
- 表达式语言语句中需要使用冒号表示属性的默认值
- 每个属性都在一个单独的表达式语言块 ${}
- && 运算符在 SpEL 块之外使用
It allows for multiple properties that have differing values and can extend to multiple properties.
它允许具有不同值的多个属性并且可以扩展到多个属性。
If you want to check more then 2 values and still maintain readability, you can use the concatenation operator between different conditions you are evaluating:
如果要检查多于 2 个值并仍保持可读性，可以在要评估的不同条件之间使用连接运算符：
Solution for more then 2 properties
超过 2 个属性的解决方案
@ConditionalOnExpression("${properties.first.property.enable:true} " +
"&& ${properties.second.property.enable:true} " +
"&& ${properties.third.property.enable:true}")
The drawback is that you cannot use a matchIfMissing argument as you would be able to when using the @ConditionalOnPropertyannotation so you will have to ensure that the properties are present in the .propertiesor YAMLfiles for all your profiles/environments or just rely on the default value
缺点是您不能像使用注释一样使用 matchIfMissing 参数，@ConditionalOnProperty因此您必须确保所有配置文件/环境的.properties或YAML文件中都存在这些属性，或者仅依赖默认值价值
回答by Tahir Hussain Mir
As far as i remember, You could use this kind of expression:
据我所知，您可以使用这种表达方式：
@ConditionalOnExpression("'${com.property1}'.equals('${com.property2}')")
for further reading here is the link
进一步阅读这里是链接
if it was helpful, please do comment so that my confusion may also get cleared.
如果有帮助，请发表评论，以便我的困惑也能得到澄清。
