SpringBoot can not get the merged configuration for List type from multiple yml properties file

I have multiple datasource , so the type is list , the original configuration is OK , as follows:

the application.yml ：

test:
  db:
    datasources:
      - url: jdbc:mysql://localhost:3306/writedb
        username: root
        password: root
      - url: jdbc: mysql://localhost:3306/readdb
        username: root
        password: root

Now ,we must extract username/password to special documents, as follows , I can not get the merged Information

change the the application.yml ：

test:
  db:
    datasources:
      - url: jdbc:mysql://localhost:3306/writedb
      - url: jdbc:mysql://localhost:3306/readdb

the application-secrets.yml :

test:
  db:
    datasources:
      - username: root
        password: root
      - username: root
        password: root

@ConfigurationProperties(prefix = "test.db")
@Configuration
public class AutoLoadDataSourceProperties {

    private List<DataSourceCommonProperties> datasources;   

    // get
        // set
}

when start the application , the url is null (but through the Environment.getProperty("test.db.datasources[0].url") ,can get the value ) , How to solve this problem ,Thanks

Comment From: wilkinsona

@crazylulululu I have updated your comment to improve the formatting. You can learn how to do so yourself in GitHub's Markdown guide.

Comment From: wilkinsona

The lack of merging is intentional. I would recommend that you use property placeholders instead:

test:
  db:
    datasources:
      - url: jdbc:mysql://localhost:3306/writedb
        username: ${test.db.datasources.write.username}
        password: ${test.db.datasources.write.password}
      - url: jdbc: mysql://localhost:3306/readdb
        username: ${test.db.datasources.read.username}
        password: ${test.db.datasources.read.password}

test:
  db:
    datasources:
      write:
        username: root
        password: root
      read:
        username: root
        password: root

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