/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
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package org.apache.logging.log4j.spi;

import java.util.Map;

import org.apache.logging.log4j.ThreadContext;
import org.apache.logging.log4j.util.StringMap;

Read-only view of the data structure that implements MDC behavior for ThreadContext. 
 ThreadContextMap implementations that also implement this interface can be accessed by applications via the ThreadContext.getThreadContextMap() method. 
See Also:
ThreadContext.getThreadContextMap()
Since:
2.8/**
 * Read-only view of the data structure that implements MDC behavior for {@link org.apache.logging.log4j.ThreadContext}.
 * <p>
 * {@code ThreadContextMap} implementations that also implement this interface can be accessed
 * by applications via the {@link ThreadContext#getThreadContextMap()} method.
 * </p>
 *
 * @see ThreadContext#getThreadContextMap()
 * @since 2.8
 */
public interface ReadOnlyThreadContextMap {

    
Clears the context.
/**
     * Clears the context.
     */
    void clear();

    
Determines if the key is in the context.
Params:
key – The key to locate.
Returns:
True if the key is in the context, false otherwise./**
     * Determines if the key is in the context.
     * @param key The key to locate.
     * @return True if the key is in the context, false otherwise.
     */
    boolean containsKey(final String key);

    
Gets the context identified by the key parameter.
This method has no side effects.
Params:
key – The key to locate.
Returns:
The value associated with the key or null./**
     * Gets the context identified by the <code>key</code> parameter.
     *
     * <p>This method has no side effects.</p>
     * @param key The key to locate.
     * @return The value associated with the key or null.
     */
    String get(final String key);

    
Gets a non-null mutable copy of current thread's context Map. 
Returns:
a mutable copy of the context./**
     * Gets a non-{@code null} mutable copy of current thread's context Map.
     * @return a mutable copy of the context.
     */
    Map<String, String> getCopy();

    
Returns an immutable view on the context Map or null if the context map is empty. 
Returns:
an immutable context Map or null./**
     * Returns an immutable view on the context Map or {@code null} if the context map is empty.
     * @return an immutable context Map or {@code null}.
     */
    Map<String, String> getImmutableMapOrNull();

    
Returns the context data for reading. Note that regardless of whether the returned context data has been frozen (made read-only) or not, callers should not attempt to modify the returned data structure. 

Thread safety note:

 If this ReadOnlyThreadContextMap implements CopyOnWrite, then the returned StringMap can safely be passed to another thread: future changes in the underlying context data will not be reflected in the returned StringMap. 
 Otherwise, if this ReadOnlyThreadContextMap does not implement CopyOnWrite, then it is not safe to pass the returned StringMap to another thread because changes in the underlying context may be reflected in the returned object. It is the responsibility of the caller to make a copy to pass to another thread. 
Returns:
a StringMap containing context data key-value pairs/**
     * Returns the context data for reading. Note that regardless of whether the returned context data has been
     * {@linkplain StringMap#freeze() frozen} (made read-only) or not, callers should not attempt to modify
     * the returned data structure.
     * <p>
     * <b>Thread safety note:</b>
     * </p>
     * <p>
     * If this {@code ReadOnlyThreadContextMap} implements {@link CopyOnWrite}, then the returned {@code StringMap} can
     * safely be passed to another thread: future changes in the underlying context data will not be reflected in the
     * returned {@code StringMap}.
     * </p><p>
     * Otherwise, if this {@code ReadOnlyThreadContextMap} does <em>not</em> implement {@link CopyOnWrite}, then it is
     * not safe to pass the returned {@code StringMap} to another thread because changes in the underlying context may
     * be reflected in the returned object. It is the responsibility of the caller to make a copy to pass to another
     * thread.
     * </p>
     *
     * @return a {@code StringMap} containing context data key-value pairs
     */
    StringMap getReadOnlyContextData();

    
Returns true if the Map is empty.
Returns:
true if the Map is empty, false otherwise./**
     * Returns true if the Map is empty.
     * @return true if the Map is empty, false otherwise.
     */
    boolean isEmpty();
}