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/*
* Copyright 2002-2023 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
*
* https://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.springframework.context;
import java.util.function.Consumer;
import org.springframework.core.ResolvableType;
import org.springframework.core.ResolvableTypeProvider;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* An {@link ApplicationEvent} that carries an arbitrary payload.
*
* @author Stephane Nicoll
* @author Juergen Hoeller
* @author Qimiao Chen
* @since 4.2
* @param the payload type of the event
* @see ApplicationEventPublisher#publishEvent(Object)
* @see ApplicationListener#forPayload(Consumer)
*/
@SuppressWarnings("serial")
public class PayloadApplicationEvent extends ApplicationEvent implements ResolvableTypeProvider {
private final T payload;
private final ResolvableType payloadType;
/**
* Create a new PayloadApplicationEvent, using the instance to infer its type.
* @param source the object on which the event initially occurred (never {@code null})
* @param payload the payload object (never {@code null})
*/
public PayloadApplicationEvent(Object source, T payload) {
this(source, payload, null);
}
/**
* Create a new PayloadApplicationEvent based on the provided payload type.
* @param source the object on which the event initially occurred (never {@code null})
* @param payload the payload object (never {@code null})
* @param payloadType the type object of payload object (can be {@code null}).
* Note that this is meant to indicate the payload type (for example, {@code String}),
* not the full event type (such as {@code PayloadApplicationEvent<<String>}).
* @since 6.0
*/
public PayloadApplicationEvent(Object source, T payload, @Nullable ResolvableType payloadType) {
super(source);
Assert.notNull(payload, "Payload must not be null");
this.payload = payload;
this.payloadType = (payloadType != null ? payloadType : ResolvableType.forInstance(payload));
}
@Override
public ResolvableType getResolvableType() {
return ResolvableType.forClassWithGenerics(getClass(), this.payloadType);
}
/**
* Return the payload of the event.
*/
public T getPayload() {
return this.payload;
}
}
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