/*
 * 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.http;

import java.util.AbstractMap;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import org.springframework.lang.Nullable;
import org.springframework.util.MultiValueMap;

HttpHeaders object that can only be read, not written to.
Author:Brian Clozel
Since:5.1.1
/** * {@code HttpHeaders} object that can only be read, not written to. * * @author Brian Clozel * @since 5.1.1 */
class ReadOnlyHttpHeaders extends HttpHeaders { private static final long serialVersionUID = -8578554704772377436L; @Nullable private MediaType cachedContentType; ReadOnlyHttpHeaders(HttpHeaders headers) { super(headers.headers); } @Override public MediaType getContentType() { if (this.cachedContentType != null) { return this.cachedContentType; } else { MediaType contentType = super.getContentType(); this.cachedContentType = contentType; return contentType; } } @Override public List<String> get(Object key) { List<String> values = this.headers.get(key); return (values != null ? Collections.unmodifiableList(values) : null); } @Override public void add(String headerName, @Nullable String headerValue) { throw new UnsupportedOperationException(); } @Override public void addAll(String key, List<? extends String> values) { throw new UnsupportedOperationException(); } @Override public void addAll(MultiValueMap<String, String> values) { throw new UnsupportedOperationException(); } @Override public void set(String headerName, @Nullable String headerValue) { throw new UnsupportedOperationException(); } @Override public void setAll(Map<String, String> values) { throw new UnsupportedOperationException(); } @Override public Map<String, String> toSingleValueMap() { return Collections.unmodifiableMap(this.headers.toSingleValueMap()); } @Override public Set<String> keySet() { return Collections.unmodifiableSet(this.headers.keySet()); } @Override public List<String> put(String key, List<String> value) { throw new UnsupportedOperationException(); } @Override public List<String> remove(Object key) { throw new UnsupportedOperationException(); } @Override public void putAll(Map<? extends String, ? extends List<String>> map) { throw new UnsupportedOperationException(); } @Override public void clear() { throw new UnsupportedOperationException(); } @Override public Collection<List<String>> values() { return Collections.unmodifiableCollection(this.headers.values()); } @Override public Set<Entry<String, List<String>>> entrySet() { return Collections.unmodifiableSet(this.headers.entrySet().stream() .map(AbstractMap.SimpleImmutableEntry::new) .collect(Collectors.toSet())); } }