org.glowroot.agent.plugin.api.weaving.Mixin Maven / Gradle / Ivy
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/*
* Copyright 2012-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.glowroot.agent.plugin.api.weaving;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Annotation to designate a class as a mixin class. The fields and methods from the mixin class
* will be added to the target types. The target types can include interfaces, in which case the
* annotated class will be mixed in to all classes which implement any of those interfaces.
*
* If the mixin class implements any interfaces, those interfaces will be added to the target types.
* This is the recommended way to access methods that are mixed in to the target types.
*
* Constructors are not mixed in to the target types, but a single method in the mixin class can be
* annotated with {@literal @}{@code MixinInit} and this will be called exactly once at some point
* during the construction of each target type (to be precise, it is called at the end of each
* target type constructor that doesn't cascade to another constructor in the same type).
*
* It's important to note that inline field initializers in the mixin class will not get added to
* the target types (since at the bytecode level they are be part of the mixin constructor), so
* field initializers must be placed in the {@literal @}{@code MixinInit}.
*/
@Target(TYPE)
@Retention(RUNTIME)
public @interface Mixin {
String[] value();
}