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java/org/apache/tomcat/util/http/ResponseUtil.java

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+/*
+ * 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
+ * limitations under the License.
+ */
+package org.apache.tomcat.util.http;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.tomcat.util.http.parser.TokenList;
+
+public class ResponseUtil {
+
+    private static final String VARY_HEADER = "vary";
+    private static final String VARY_ALL = "*";
+
+    private ResponseUtil() {
+        // Utility class. Hide default constructor.
+    }
+
+
+    public static void addVaryFieldName(MimeHeaders headers, String name) {
+        addVaryFieldName(new HeaderAdapter(headers), name);
+    }
+
+
+    public static void addVaryFieldName(HttpServletResponse response, String name) {
+        addVaryFieldName(new ResponseAdapter(response), name);
+    }
+
+
+    private static void addVaryFieldName(Adapter adapter, String name) {
+
+        Collection<String> varyHeaders = adapter.getHeaders(VARY_HEADER);
+
+        // Short-cut if only * has been set
+        if (varyHeaders.size() == 1 && varyHeaders.iterator().next().trim().equals(VARY_ALL)) {
+            // No need to add an additional field
+            return;
+        }
+
+        // Short-cut if no headers have been set
+        if (varyHeaders.size() == 0) {
+            adapter.addHeader(VARY_HEADER, name);
+            return;
+        }
+
+        // Short-cut if "*" is added
+        if (VARY_ALL.equals(name.trim())) {
+            adapter.setHeader(VARY_HEADER, VARY_ALL);
+            return;
+        }
+
+        // May be dealing with an application set header, or multiple headers.
+        // Header names overlap so can't use String.contains(). Have to parse
+        // the existing values, check if the new value is already present and
+        // then add it if not. The good news is field names are tokens which
+        // makes parsing simpler.
+        Set<String> fieldNames = new HashSet<>();
+
+        for (String varyHeader : varyHeaders) {
+            StringReader input = new StringReader(varyHeader);
+            try {
+                TokenList.parseTokenList(input, fieldNames);
+            } catch (IOException ioe) {
+                // Should never happen
+            }
+        }
+
+        if (fieldNames.contains(VARY_ALL)) {
+            // '*' has been added without removing other values. Optimise.
+            adapter.setHeader(VARY_HEADER, VARY_ALL);
+            return;
+        }
+
+        // Build single header to replace current multiple headers
+        // Replace existing header(s) to ensure any invalid values are removed
+        fieldNames.add(name);
+        StringBuilder varyHeader = new StringBuilder();
+        varyHeader.append(name);
+        for (String fieldName : fieldNames) {
+            varyHeader.append(',');
+            varyHeader.append(fieldName);
+        }
+        adapter.setHeader(VARY_HEADER, varyHeader.toString());
+    }
+
+
+    private static interface Adapter {
+
+        Collection<String> getHeaders(String name);
+
+        void setHeader(String name, String value);
+
+        void addHeader(String name, String value);
+    }
+
+
+    private static final class HeaderAdapter implements Adapter {
+        private final MimeHeaders headers;
+
+        public HeaderAdapter(MimeHeaders headers) {
+            this.headers = headers;
+        }
+
+        @Override
+        public Collection<String> getHeaders(String name) {
+            Enumeration<String> values = headers.values(name);
+            List<String> result = new ArrayList<>();
+            while (values.hasMoreElements()) {
+                result.add(values.nextElement());
+            }
+            return result;
+        }
+
+        @Override
+        public void setHeader(String name, String value) {
+            headers.setValue(name).setString(value);
+        }
+
+        @Override
+        public void addHeader(String name, String value) {
+            headers.addValue(name).setString(value);
+        }
+    }
+
+
+    private static final class ResponseAdapter implements Adapter {
+        private final HttpServletResponse response;
+
+        public ResponseAdapter(HttpServletResponse response) {
+            this.response = response;
+        }
+
+        @Override
+        public Collection<String> getHeaders(String name) {
+            return response.getHeaders(name);
+        }
+
+        @Override
+        public void setHeader(String name, String value) {
+            response.setHeader(name, value);
+        }
+
+        @Override
+        public void addHeader(String name, String value) {
+            response.addHeader(name, value);
+        }
+    }
+}