spring-kafka HeaderEnricher 源码
spring-kafka HeaderEnricher 代码
文件路径：/spring-kafka/src/main/java/org/springframework/kafka/streams/HeaderEnricher.java
/*
* Copyright 2019 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.kafka.streams;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;
import org.apache.kafka.common.header.Headers;
import org.apache.kafka.common.header.internals.RecordHeader;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.kstream.Transformer;
import org.apache.kafka.streams.processor.ProcessorContext;
import org.springframework.expression.Expression;
/**
* Manipulate the headers.
*
* @param <K> the key type.
* @param <V> the value type.
*
* @author Gary Russell
* @since 2.3
*
*/
public class HeaderEnricher<K, V> implements Transformer<K, V, KeyValue<K, V>> {
private final Map<String, Expression> headerExpressions = new HashMap<>();
private ProcessorContext processorContext;
public HeaderEnricher(Map<String, Expression> headerExpressions) {
this.headerExpressions.putAll(headerExpressions);
}
@Override
public void init(ProcessorContext context) {
this.processorContext = context;
}
@Override
public KeyValue<K, V> transform(K key, V value) {
Headers headers = this.processorContext.headers();
Container<K, V> container = new Container<>(this.processorContext, key, value);
this.headerExpressions.forEach((name, expression) -> {
Object headerValue = expression.getValue(container);
if (headerValue instanceof String) {
headerValue = ((String) headerValue).getBytes(StandardCharsets.UTF_8);
}
else if (!(headerValue instanceof byte[])) {
throw new IllegalStateException("Invalid header value type: " + headerValue.getClass());
}
headers.add(new RecordHeader(name, (byte[]) headerValue));
});
return new KeyValue<>(key, value);
}
@Override
public void close() {
// NO-OP
}
/**
* Container object for SpEL evaluation.
*
* @param <K> the key type.
* @param <V> the value type.
*
*/
public static final class Container<K, V> {
private final ProcessorContext context;
private final K key;
private final V value;
private Container(ProcessorContext context, K key, V value) {
this.context = context;
this.key = key;
this.value = value;
}
public ProcessorContext getContext() {
return this.context;
}
public K getKey() {
return this.key;
}
public V getValue() {
return this.value;
}
}
}
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