com.datastax.util.concurrency.GuardedBy Maven / Gradle / Ivy

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package com.datastax.util.concurrency;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * The presence of this annotation indicates that the field or method must only be accessed when holding the specified
 * lock.
 */
@Documented
@Target(value = {FIELD, METHOD})
@Retention(RUNTIME)
public @interface GuardedBy {
    /**
     * The specified lock that guards the annotated field or method. Valid values are:
     * 
     * {@code this} indicates the intrinsic lock of the instance containing the field or method.
     * class-name.this which allows for disambiguation of which {@code this} when dealing
     * with inner classes
     * {@code itself} which is valid for reference fields only, and indicates that the referenced instance's
     * own intrinsic lock should be used as the guard
     * field-name indicates the named instance or static field is to be used as the guard. If
     * the field type is not a sub-type of {@link java.util.concurrent.locks.Lock} then the intrinsic lock of
     * the referenced instance is to be used
     * class-name.field-name indicates the named static field is to be used as the
     * guard. If the field type is not a sub-type of {@link java.util.concurrent.locks.Lock} then the intrinsic lock of
     * the referenced instance is to be used
     * method-name() indicates that the zero-argument method should be called to obtain the
     * lock object. If the return type is not a sub-type of {@link java.util.concurrent.locks.Lock} then the intrinsic
     * lock of the returned instance is to be used
     * class-name.class indicates that the intrinsic lock of the specified class should be used
     * as the guard
     * 
     *
     * @return The specified lock that guards the annotated field or method
     */
    String value();
}