如何在不同的类中使用相同的对象及其值

Question

Here i have a method getAWSCredential which returns cred with some value in it.

@Override
    public AWSCredentialDTO getAWSCredential(String user_name) {
        AWSCredentialDTO cred= (AWSCredentialDTO) entityManager.createNativeQuery("select * from aws_user_credentials a where a.user_name=:userName",AWSCredentialDTO.class)
        .setParameter("userName", user_name).getSingleResult();
        return cred;

    }

Here I have one more service ec2 where I need to make use of values returned in cred in previous method.

private AmazonEC2 ec2;

    public AmazonEC2 ec2() {
        BasicAWSCredentials awsCreds = new BasicAWSCredentials(aws_access_key_id,
                aws_secret_access_key);
        return AmazonEC2ClientBuilder.standard().withCredentials(new AWSStaticCredentialsProvider(awsCreds))
                .withRegion(Regions.AP_SOUTH_1).build();
    }

Both the above methods are separate classes. First I will run the getAWSCredential and then I will invoke ec2 where I need to make use of the values of cred . Can anyone suggest me how can I achieve this? This is a spring boot application.

Answer 1

Maybe you'd like to use DependencyInjection for it if the credentials are global or on a context, you can create a bean that either stores the credentials or the EC2 instance as a proxy to access it within the context of the session of the user.

Please specify if you have a single username/password or you've got multiple and the different requests need to be served using a username or another.

If you've got a single, you can create an API Key and set it in application.properties . You can use cloud.aws.credentials.accessKey and cloud.aws.credentials.secretKey .

Answer 2

You would have to create a spring bean of the class containing getAWSCredential and autowire it in the class which needs it. Check the sample code below.

@Component
public class AmazonUtil {
    ...

    @Override
    public AWSCredentialDTO getAWSCredential(String user_name) {
        AWSCredentialDTO cred= (AWSCredentialDTO) entityManager.createNativeQuery("select * from aws_user_credentials a where a.user_name=:userName",AWSCredentialDTO.class)
        .setParameter("userName", user_name).getSingleResult();
        return cred;
    }
}

@Component
public class Test {
    @Autowired
    private AmazonUtil amazonUtil;

    public AmazonEC2 ec2(String userName) {
        AWSCredentialDTO credsDto = amazonUtil.getAWSCredential(userName);

        BasicAWSCredentials awsCreds = ...construct using credsDto

        return AmazonEC2ClientBuilder.standard().withCredentials(new AWSStaticCredentialsProvider(awsCreds))
                .withRegion(Regions.AP_SOUTH_1).build();
    }
}

Answer 3

Create a separate class say ClassCred and create an object for ClassCred within the same class ClassCred credObj = new ClassCred() . Get the credObj from getAWSCredential(String user_name) method and set the cred returned by getAWSCredential method to credObj . Now the object credObj hass the value cred returned by getAWSCredential method. Now from your ec2() method you can invoke the credObj and get the values stored in it.