OpenJDK 27 · jdk.jfr.consumer · APIdia, the JavaDoc alternative

This package contains classes for consuming Flight Recorder data.

In the following example, the program prints a histogram of all method samples in a recording.

public static void main(String[] args) throws IOException {
    if (args.length != 1) {
        System.err.println("Must specify a recording file.");
        return;
    }

    RecordingFile.readAllEvents(Path.of(args[0])).stream()
        .filter(e -> e.getEventType().getName().equals("jdk.ExecutionSample"))
        .map(e -> e.getStackTrace())
        .filter(s -> s != null)
        .map(s -> s.getFrames().getFirst())
        .filter(f -> f.isJavaFrame())
        .map(f -> f.getMethod())
        .collect(
            Collectors.groupingBy(m -> m.getType().getName() + "." + m.getName() + " " + m.getDescriptor(),
            Collectors.counting()))
        .entrySet()
        .stream()
        .sorted((a, b) -> b.getValue().compareTo(a.getValue()))
        .forEach(e -> System.out.printf("%8d %s\n", e.getValue(), e.getKey()));
}

Null-handling

All methods define whether they accept or return null in the Javadoc. Typically this is expressed as "not null". If a null parameter is used where it is not allowed, a java.lang.NullPointerException is thrown. If a null parameter is passed to a method that throws other exceptions, such as java.io.IOException, the java.lang.NullPointerException takes precedence, unless the Javadoc for the method explicitly states how null is handled, i.e. by throwing java.lang.IllegalArgumentException.

Modifier and Type	Interface and Description
public interface	EventStream Represents a stream of events.

Class Summary

Modifier and Type	Class and Description
public class	MetadataEvent Event that contains information about event types and configurations.
public class	RecordedClass A recorded Java type, such as a class or an interface.
public class	RecordedClassLoader A recorded Java class loader.
public class	RecordedEvent A recorded event.
public class	RecordedFrame A recorded frame in a stack trace.
public class	RecordedMethod A recorded method.
public class	RecordedObject A complex data type that consists of one or more fields.
public class	RecordedStackTrace A recorded stack trace.
public class	RecordedThread A recorded thread.
public class	RecordedThreadGroup A recorded Java thread group.
public class	RecordingFile A recording file.
public class	RecordingStream A recording stream produces events from the current JVM (Java Virtual Machine).

Package jdk.jfr.consumer

Interface Summary

Class Summary