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Can you reference Azure Key Vault secrets inside application.properties?

I have a record:
#ConfigurationProperties("service.api")
#ConstructorBinding
public record ServiceApiConfig(String clientId, String clientSecret) {}
and an application.properties file:
service.api.client_id=client_id
service.api.client_secret=client_secret
and the binding works when I'm doing local development.
What I want to do is to use Azure services (Azure Spring Apps, Key Vault, etc.) and my question is whether I can, inside application.properties file, reference secrets stored in the Key Vault. Something like this:
service.api.client_id=<name-of-the-id-kept-in-the-vault>
service.api.client_secret=<name-of-the-secret-kept-in-the-vault>
Tutorials I've seen make me think that the only way to do the binding is by using #Value("${nameOfTheSecret}") annotation on fields in java classes. Is it possible to do it in a way that I want?

You can reference Azure Key Vault secrets inside the application.properties file by adding the below properties of azure key vault which you want to connect from the spring boot application:
spring.cloud.azure.keyvault.secret.property-sources[0].credential.client-id=<your client ID>
spring.cloud.azure.keyvault.secret.property-sources[0].credential.client-secret=<your client key>
spring.cloud.azure.keyvault.secret.property-sources[0].endpoint=https://contosokv.vault.azure.net/
spring.cloud.azure.keyvault.secret.property-sources[0].profile.tenant-id=<your tenant ID>

Read value from AWS Secrets Manager and replace a placeholder in the Springboot property values

Our application needs to connect to confluent kafka and thus we have the following setups inside application.yaml file
kafka:
properties:
sasl:
mechanism: PLAIN
jaas:
config: org.apache.kafka.common.security.plain.PlainLoginModule required username={userName} password={passWord};
The {userName} and {passWord} need to be replaced by value fetching from AWS secret manager. These are what I have done so far.
Step 1: Use the following maven dependency
<dependency>
<groupId>com.amazonaws</groupId>
<artifactId>aws-java-sdk-secretsmanager</artifactId>
</dependency>
Step 2: Create a configuration class and create a method annotated with #Bean to init a AWSSecretsManager client object.And we can get some key value pairs by using AWSSecretsManager object.
// Create a Secrets Manager client
AWSSecretsManager client = AWSSecretsManagerClientBuilder.standard()
.withRegion(region)
.withCredentials(new AWSStaticCredentialsProvider(new BasicAWSCredentials(accessKey, secretKey)))
.build();
I have the following questions to ask:
How can we inject the value we get from secret manager and replace the placeholder in the application.yml file?
To access AWSSecretsManager we need to pass AWS accessKey and seretKey. What is a good practice to provide those two values?
Some more info:
our application will be running on AWS ECS

I wouldn't recommend doing this via Java code at all. I would totally remove the aws-java-sdk-secretsmanager dependency, and use the ECS support for injecting SecretsManager values as environment variables.

My answer here will focus on the Secrets Manager API part of your question
I recommend that you move from AWS SDK for Java V1 to AWS SDK for Java V2. You can find V2 Java Secret Manager examples here.
https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/javav2/example_code/secretsmanager
Here is the Service Client for V2.
SecretsManagerClient secretsClient = SecretsManagerClient.builder()
.region(region)
.credentialsProvider(ProfileCredentialsProvider.create())
.build();
In this example, I am using a ProfileCredentialsProvider that reads creds from .aws/Credentials. You can learn more about how V2 handles creds in the AWS Java V2 DEV Guide.
Using credentials
You cannot use ProfileCredentialsProvider in an app deployed to a container as this file structure not part of the container. So you can use Amazon ECS container credentials:
The SDK uses the ContainerCredentialsProvider class to load credentials from the AWS_CONTAINER_CREDENTIALS_RELATIVE_URI system environment variable.
See point 5 in the above Doc.

Alternate way of providing Credentials to Spring Cloud GCP

I am trying to use the Spring Cloud GCP. I want to know how to programmatically load GCP credentials rather than loading the GCP credentials from a json file using spring.cloud.gcp.credentials.location .
Does creating a bean of type com.google.auth.Credentials let Spring-Boot auto-configure Spring-Cloud-GCP correctly to use within the application?
If not, what is the way to inject Credentials so that Spring Cloud GCP is configured correctly?

Not Credentials, but a bean of type CredentialsProvider will take precedence over any properties/autoconfiguration.
It's a functional interface, so you can return a lambda:
#Bean
public CredentialsProvider credentialsProvider() {
return () -> NoCredentialsProvider.create().getCredentials();
}

FixedCredentialsProvider gives unauthorized exception when calling Google Cloud service

I am trying to call Google Cloud DocumentAI through a google service account. I have the json key that was generated for it and I load it into my application via the FixedCredentialsProvider and a GoogleCredentials object since it's not possible to load it via environment variables for my use case. This method used to work but now it throws an UNAUTHORIZED exception and something related to not having valid OAuth2 tokens. When I test the scenario using the GOOGLE_APPLICATION_CREDENTIALS env variable it works fine. Has there been a change that doesn't allow the FixedCredentials method anymore? I have not updated the sdk, it just stopped on its own. Is there a new way to load the credentials JSON key programmatically?

Ended up inspecting the SDK source to find the answer. The difference between loading via environment variables and using the GoogleCredentials is that in the latter case it does not provide OAuth2 scopes which is something that since last testing has become mandatory from Google's side for DocumentAI service. Loading the key using the environment variables goes from a different code path that provides some default scopes. We can provide the same scopes manually when loading via GoogleCredentials like so:
GoogleCredentials googleCredentials = GoogleCredentials
.fromStream(new FileInputStream(jsonKeyFile))
.createScoped(DocumentUnderstandingServiceSettings.getDefaultServiceScopes());
DocumentUnderstandingServiceClient client = DocumentUnderstandingServiceClient.create(
DocumentUnderstandingServiceSettings.newBuilder()
.setCredentialsProvider(FixedCredentialsProvider.create(googleCredentials))
.build()
);
The DocumentUnderstandingServiceSettings.getDefaultServiceScopes() returns a static variable that contains the same scopes that are used by the environment variable loading method which in turn enables usage of DocumentAI with the manually created GoogleCredentials.

Get keyvault secrets using Spring api with Managed Service Identities

Due to some new security requirments the api I'm developing now is required to store several urls, azure account names etc. in the azure key vault, rather than in the application.yml config file.
The issue is that I'm having trouble authenticating / accessing the key vault client in a Local environment. I have very limited access to the azure functions / key vault itself so testing the new code I'm writing is near impossible at current:
public String getSecretFromKeyVault(String key) {
/**
* Breaks in the constructor call, as the system.env variables for MSI_ENDPOINT and MSI_SECRET are null.
**/
AppServiceMSICredentials credentials = new AppServiceMSICredentials(AzureEnvironment.AZURE);
KeyVaultClient client = new KeyVaultClient(credentials);
SecretBundle secret = client.getSecret("url-for-key-vault", key);
return secret.value();
}
I'm aware that the variables will be set in the cloud server, but my question is how can I best verify that the vault calls have been implemented properly(unit, integration, e2e local tests), and how would I manage to use key vault calls during local development / runtime?
The alternative to MSI would be to enter the client id and key manually, following authentication against the active directory. This could be a solution for local development, but Would still require the declaration of confidential information in the source code.
Ive also tried logging in to azure using az login before running the server but that didn't work either.
Does anyone have any suggestions on how I might resolve this issue, or what my best options are going forward?
Notes on application:
Java version: 8
Spring boot
Azure / vsts development and deployment environment

Since you're using spring-boot you may be better off using Microsoft's property source implementation that maps the keyvault properties into Spring properties and for local development and testing you set equivalent properties in property files.
Use Spring profiles. let's say you have azure and local profiles. In your application-azure.yml file configure your app to use keyvault:
# endpoint on the azure internal network for getting the identity access token
MSI_ENDPOINT: http://169.254.169.254/metadata/identity/oauth2/token
MSI_SECRET: unused
# this property triggers the use of keyvault for properties
azure.keyvault:
uri: https://<your-keyvault-name>.vault.azure.net/
Now you can inject secret properties from the spring context into your variables and they will be read from keyvault:
#Value("${superSecretValue}")
String secretValue;
To make this work locally for testing, in your application-local.yml file you can set the secret property to something appropriate:
superSecretValue: dummy-for-testing-locally
The Azure dependency you need to add to build.gradle is:
implementation "com.microsoft.azure:azure-keyvault-secrets-spring-boot-starter:2.1.6"
Run your spring-boot jar with azure as the active profile when deployed, and local when testing and developing away from azure. This is tested and working with azure java containers.