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CompositeConfiguration in log4j2 using springboot

I am working in spring boot project and I stuck in an issue. Following is the problem.
I have two log4j2 configuration file. Log4j2-1.yml and Log4j2-2.yml. Log4j2-1.yml consist the common configuration to avoid repetition duplicate configuration while Log4j2-2.yml consists application specific log config. I need to use these two log4j2 configuration in my application at same time. Please help me to configure these files in my application.\
I tried log4j2.configurationFile also but could not succeed.

Spring Boot has a custom logging configuration process that occurs just after the Log4j2 automatic configuration (its exact logic is in Log4j2LoggingSystem and is documented in Core Features). You can analyze the process by setting -Dlog4j2.debug=true.
To create a composite configuration you need to use two Spring Boot properties (cf. core properties):
logging.config=classpath:Log4j2-1.yml
logging.log4j2.config.override=classpath:Log4j2-2.yml

Spring boot application startup stuck loading hibernate files

I am using spring boot application with hibernate to connect to postgressql, but when I am running my application with run as spring boot app the starting of server is stuck with loading hibernate files
without any error, I am stuck on this and it's not also showing any error.
Does anyone have any idea?

Add the following to your app properties
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults=false
or in your code the below
properties.setProperty("hibernate.temp.use_jdbc_metadata_defaults", "false");
Hope it helps!

There was another instance of Postgresql server was running and i was also not able to kiss the process that's why the application was stuck, i restarted my system and its working fine

If you are using JPA, check your repository configuration. Spring can spend a very long time scanning for JPA repositories if you don't have basePackages or basePackageClasses set in your #EnableJpaRepositories annotation (this can be added by JpaRepositoriesAutoConfiguration if your setup meets that class's #ConditionalOn requirements).

How do I debug RestTemplate using Logback in Spring Boot?

I've been trying to figure out what I'm missing with my RestTemplate setup (particularly OAuth2RestTemplate) so I want to see the logs for debugging. I found one possible solution for it, but nothing about the operation of the RestTemplate gets shown.
What I've done so far is to replace the default Logback logging mechanism in my Spring Boot app by following the configuration shown here. When I run my Spring Boot application after changing the logging dependencies, all I see on the console is the Spring logo (in ASCII) and nothing else. I've already defined a log4j-spring.properties in src/main/resources with the property defined in the previous link.
What else am I missing here? Do I need to run my Spring Boot app in debug mode? If so, how do I do that? Also, how do I set this up using the default Logback mechanism?

Spring-Boot multiple db target dependencies

Is there a 'community/Spring' approved method with Boot to have different datasource target for the same project?
Should I include both connector (H2 and Mysql) in the project dependencies and just change the jdbc url in my application.yml?
We are switching our tomcat instance to a Boot project, old habits of having jdbc jar as provided. I was wondering if this was still supported or desired in a boot fat jar/war exec.

If I understood Your question correctly, there are two scenarios, that You could be intrested in.
First is where You use both datasources at once in your project (ex. getting data from both H2 and MySQL in the same time, or one after another).
Second scenario is when You use two datasources but not at once, for example: H2 for test/debug project build, MySQL for production. Another sub-scenario is like You want something like primary/secondary datasources.
Solution for first scenario is to add two dependencies, disable Boot autoconfiguration (autoconfiguration won't work for multiple datasources) for databases and manually configure tho separate EntityManagers etc. (more info here: https://docs.spring.io/spring-boot/docs/current/reference/html/howto-data-access.html#howto-use-two-entity-managers)
Sorry that I can't provide any code sample but I can't access my work repo from home.
Moving to the second scenario what You can do is, use profiles.
You have to create separate profile and application-something.yml file for that profile. Inside you configure your second datasource, and then in dependencies you can make your second database dependency to add only with specific profile as well - but here im not 100% sure, I don't remember how we did it in work ;d.
And again, I cant paste any example but here is some help:
Profiles,
Profile-specific configuration files
An then there is a sub-scenario that I mentioned earlier. Marking datasource as #Primary But here I've never used it, I just know it exists: Link
Edit2: After some rethinking, I think this is the way to go with Boot and active profiles: Spring Boot Maven Plugin
Sorry for a lot of spam, and reconsiderations. That was quite confusing for sure.
Hope that helps,

Separate properties file for multiple environments

I am trying to have separate property files for prod and dev environment.
I have two property files application-prod.properties, application-dev.properties placed in classpath:/config
I added VM option -Dspring.profiles.active=dev
According to what I understand from the documentation and many other references on the web, on accessing Spring Environment as environment.getProperty("") the property in "application-dev.properties" should be loaded. However, I am getting null and as it seems the property files are not read by Spring.
I also tried defining both the files in #PropertySource. Doing this, the file defined second is picked up and the corresponding property is returned. Spring is not choosing the file based on the active profile.
Am I missing something?
I also came across a issue raised through some SO questions, but I am not sure if it refers to the same problem.

Right, so documentation you are pointing to is from Spring Boot project. That is not the same as Spring Framework. If you are not using Spring Boot, -Dspring.profiles.active=dev wouldn't work.
You have two options:
Introduce Spring Boot to your project ans turn on auto-configuration (#SpringBootApplication or #EnableAutoConfiguration).
Use plain Spring Framework features like PropertyPlaceholderConfigurer, but it doesn't give you same flexibility as Spring Boot features and you will need to create some boilerplate code to handle various envs.