Evaluate property-configuration mechanisms

Component uses Properties directly, performing type conversion and error checking as appropriate.

org.springframework.core.env.Environment is not a good approach, but it could be useful when the name of the property you need to access changes dynamically.

@Component
@RequiredArgsConstructor
public class Example {

private Environment env;
....

public void method(String pathPropertyName) {
    .....  
    String path = env.getProperty(pathPropertyName);
    .....
}

Component uses org.springframework.beans.factory.annotation.Value, which reads from properties and performs all type conversion and error checking

    @Value("${security.enable-csrf:true}")
    private boolean csrfEnabled = true;

Other approach using property configuration.

    @Scheduled(
            fixedRateString = "${runtime.participantParameters.heartBeatMs}",
            initialDelayString = "${runtime.participantParameters.heartBeatMs}")
    public void schedule() { 
}

@ConfigurationProperties can be used to map values from .properties( .yml also supported) to a POJO. It performs all type conversion and error checking using validation javax.validation.constraints

@Validated
@Getter
@Setter
@ConfigurationProperties(prefix = "runtime")
public class ClRuntimeParameterGroup {
    @Min(100)
    private long heartBeatMs;

    @Valid
    @Positive
    private long reportingTimeIntervalMs;

    @Valid
    @NotNull
    private ParticipantUpdateParameters updateParameters;

    @NotBlank
    private String description; 
}

Convert org.onap.policy.common.parameters.BeanValidationResult to Spring validator using org.onap.policy.common.parameters.validation.ParameterGroupConstraint

    @NotNull
    @ParameterGroupConstraint
    private TopicParameterGroup topicParameterGroup;