org.springframework.messaging.MessageHeaders Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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.springframework.messaging;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.AlternativeJdkIdGenerator;
import org.springframework.util.IdGenerator;
/**
* The headers for a {@link Message}.
*
* IMPORTANT: This class is immutable. Any mutating operation such as
* {@code put(..)}, {@code putAll(..)} and others will throw
* {@link UnsupportedOperationException}.
*
Subclasses do have access to the raw headers, however, via {@link #getRawHeaders()}.
*
*
One way to create message headers is to use the
* {@link org.springframework.messaging.support.MessageBuilder MessageBuilder}:
*
* MessageBuilder.withPayload("foo").setHeader("key1", "value1").setHeader("key2", "value2");
*
*
* A second option is to create {@link org.springframework.messaging.support.GenericMessage}
* passing a payload as {@link Object} and headers as a {@link Map java.util.Map}:
*
* Map headers = new HashMap();
* headers.put("key1", "value1");
* headers.put("key2", "value2");
* new GenericMessage("foo", headers);
*
*
* A third option is to use {@link org.springframework.messaging.support.MessageHeaderAccessor}
* or one of its subclasses to create specific categories of headers.
*
* @author Arjen Poutsma
* @author Mark Fisher
* @author Gary Russell
* @author Juergen Hoeller
* @since 4.0
* @see org.springframework.messaging.support.MessageBuilder
* @see org.springframework.messaging.support.MessageHeaderAccessor
*/
public class MessageHeaders implements Map, Serializable {
/**
* UUID for none.
*/
public static final UUID ID_VALUE_NONE = new UUID(0,0);
/**
* The key for the Message ID. This is an automatically generated UUID and
* should never be explicitly set in the header map except in the
* case of Message deserialization where the serialized Message's generated
* UUID is being restored.
*/
public static final String ID = "id";
/**
* The key for the message timestamp.
*/
public static final String TIMESTAMP = "timestamp";
/**
* The key for the message content type.
*/
public static final String CONTENT_TYPE = "contentType";
/**
* The key for the message reply channel.
*/
public static final String REPLY_CHANNEL = "replyChannel";
/**
* The key for the message error channel.
*/
public static final String ERROR_CHANNEL = "errorChannel";
private static final long serialVersionUID = 7035068984263400920L;
private static final Log logger = LogFactory.getLog(MessageHeaders.class);
private static final IdGenerator defaultIdGenerator = new AlternativeJdkIdGenerator();
@Nullable
private static volatile IdGenerator idGenerator;
private final Map headers;
/**
* Construct a {@link MessageHeaders} with the given headers. An {@link #ID} and
* {@link #TIMESTAMP} headers will also be added, overriding any existing values.
* @param headers a map with headers to add
*/
public MessageHeaders(@Nullable Map headers) {
this(headers, null, null);
}
/**
* Constructor providing control over the ID and TIMESTAMP header values.
* @param headers a map with headers to add
* @param id the {@link #ID} header value
* @param timestamp the {@link #TIMESTAMP} header value
*/
protected MessageHeaders(@Nullable Map headers, @Nullable UUID id, @Nullable Long timestamp) {
this.headers = (headers != null ? new HashMap<>(headers) : new HashMap<>());
if (id == null) {
this.headers.put(ID, getIdGenerator().generateId());
}
else if (id == ID_VALUE_NONE) {
this.headers.remove(ID);
}
else {
this.headers.put(ID, id);
}
if (timestamp == null) {
this.headers.put(TIMESTAMP, System.currentTimeMillis());
}
else if (timestamp < 0) {
this.headers.remove(TIMESTAMP);
}
else {
this.headers.put(TIMESTAMP, timestamp);
}
}
/**
* Copy constructor which allows for ignoring certain entries.
* Used for serialization without non-serializable entries.
* @param original the MessageHeaders to copy
* @param keysToIgnore the keys of the entries to ignore
*/
private MessageHeaders(MessageHeaders original, Set keysToIgnore) {
this.headers = new HashMap<>(original.headers.size());
original.headers.forEach((key, value) -> {
if (!keysToIgnore.contains(key)) {
this.headers.put(key, value);
}
});
}
protected Map getRawHeaders() {
return this.headers;
}
protected static IdGenerator getIdGenerator() {
IdGenerator generator = idGenerator;
return (generator != null ? generator : defaultIdGenerator);
}
@Nullable
public UUID getId() {
return get(ID, UUID.class);
}
@Nullable
public Long getTimestamp() {
return get(TIMESTAMP, Long.class);
}
@Nullable
public Object getReplyChannel() {
return get(REPLY_CHANNEL);
}
@Nullable
public Object getErrorChannel() {
return get(ERROR_CHANNEL);
}
@SuppressWarnings("unchecked")
@Nullable
public T get(Object key, Class type) {
Object value = this.headers.get(key);
if (value == null) {
return null;
}
if (!type.isAssignableFrom(value.getClass())) {
throw new IllegalArgumentException("Incorrect type specified for header '" +
key + "'. Expected [" + type + "] but actual type is [" + value.getClass() + "]");
}
return (T) value;
}
// Delegating Map implementation
public boolean containsKey(Object key) {
return this.headers.containsKey(key);
}
public boolean containsValue(Object value) {
return this.headers.containsValue(value);
}
public Set> entrySet() {
return Collections.unmodifiableMap(this.headers).entrySet();
}
@Nullable
public Object get(Object key) {
return this.headers.get(key);
}
public boolean isEmpty() {
return this.headers.isEmpty();
}
public Set keySet() {
return Collections.unmodifiableSet(this.headers.keySet());
}
public int size() {
return this.headers.size();
}
public Collection