英文:
How does the ${} in spring worked ,why it could take the environment value into spring context?
问题
简而言之，我在我的环境中定义了一个变量：
export host=localhost
并且在Spring中，我的JDBC URL是：
spring.datasource.url=jdbc://${host}://root...
配置完成后，Spring中的URL将变为：
spring.datasource.url=jdbc://localhost://root...
所以，有人能解释一下Spring所做的工作是什么吗？或者我应该查看哪篇Spring文章？
英文:
In a NutShell , i define a variables at my environment
export host=localhost
and my jdbc url in spring is spring.datasource.url=jdbc://${host}://root....
after the config work done , the url in spring would be spring.datasource.url=jdbc://localhost://root... ,so could someone explain what the effort that spring had done ? or which article should i take a look in spring ?
答案1
得分: -1
在这种情况下，让我们分解一下步骤以及Spring在这个过程中的作用：
-
环境变量：你定义了一个名为“host”的环境变量，其值为“localhost”。通常这样做是为了使你的应用程序可配置，并允许根据环境使用不同的值。
-
Spring配置：在你的Spring配置文件中，你有一个名为
spring.datasource.url的属性，它保存了数据库连接的JDBC URL。URL中的${host}占位符表示应该用“host”环境变量的值替换它。 -
Spring属性解析：当Spring初始化应用程序上下文时，它会扫描配置文件并解析属性。在这种情况下，它识别出
spring.datasource.url中的${host}占位符。 -
占位符替换：Spring将
${host}占位符替换为“host”环境变量的实际值，即“localhost”。因此，最终的JDBC URL变成了jdbc://localhost://root...。
这种方法的主要好处是允许你动态配置JDBC URL，而无需修改代码并每次部署新的JAR文件。
英文:
In the scenario lets break down the steps and the role of Spring in this process:
-
Environment Variable: You defined an environment variable named "host" with the value "localhost". This is typically done to make your application configurable and allow different values based on the environment
-
Spring Configuration: In your Spring configuration file, you have a property named
spring.datasource.urlwhich holds the JDBC URL for your database connection. The${host}placeholder within the URL indicates that it should be replaced with the value of the "host" environment variable. -
Spring Property Resolution: When Spring initializes the application context, it scans the config files and resolves the properties. In this case, it identifies the "${host}" placeholder within the
spring.datasource.url. -
Placeholder Replacement: Spring replaces the "${host}" placeholder with the actual value of the "host" environment variable, which is "localhost". As a result, the final JDBC URL becomes
jdbc://localhost://root...
The main benefit of this approach is that it allows you to dynamically configure the JDBC URL without modifying the code and delpoy new jar file each time
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