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/OpenJDK 21

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.

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

@MetadataDefinition
@Label("Transaction Id")
@Relational
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.FIELD })
public @interface TransactionId {
}

@Severity(80)
@Label("Transaction Blocked")
class TransactionBlocked extends Event {
    @TransactionId
    @Label("Transaction")
    long transactionId1;

    @TransactionId
    @Label("Transaction Blocker")
    long transactionId2;
}
Adding @MetadataDefinition to the declaration of @Severity and @TransactionId ensures the information is saved by Flight Recorder.
Since:
9

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Documentation extracted from Debian's OpenJDK Development Kit package.
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.jfr/jdk/jfr/MetadataDefinition.html