Module jdk.jfr
Package jdk.jfr

Annotation Interface MetadataDefinition

@Retention(RUNTIME) @Target(TYPE) public @interface MetadataDefinition
Meta annotation for defining new types of event metadata.

In the following example, a transaction event is defined with two user-defined annotations, @Severity and @TransactionId.

@Description("Value between 0 and 100 that indicates severity. 100 is most severe.")
@Target({ ElementType.TYPE })
public @interface Severity {
    int value() default 50;

@Label("Transaction Id")
@Target({ ElementType.FIELD })
public @interface TransactionId {

@Label("Transaction Blocked")
class TransactionBlocked extends Event {
    long transactionId1;

    @Label("Transaction Blocker")
    long transactionId2;
Adding @MetadataDefinition to the declaration of @Severity and @TransactionId ensures the information is saved by Flight Recorder.