Java tutorial
/* * 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 com.squareup.okhttp; import com.squareup.okhttp.internal.http.HttpDate; import java.util.ArrayList; import java.util.Collections; import java.util.Date; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import java.util.Set; import java.util.TreeSet; /** * The header fields of a single HTTP message. Values are uninterpreted strings; * use {@code Request} and {@code Response} for interpreted headers. This class * maintains the order of the header fields within the HTTP message. * * <p>This class tracks header values line-by-line. A field with multiple comma- * separated values on the same line will be treated as a field with a single * value by this class. It is the caller's responsibility to detect and split * on commas if their field permits multiple values. This simplifies use of * single-valued fields whose values routinely contain commas, such as cookies * or dates. * * <p>This class trims whitespace from values. It never returns values with * leading or trailing whitespace. * * <p>Instances of this class are immutable. Use {@link Builder} to create * instances. */ public final class Headers { private final String[] namesAndValues; private Headers(Builder builder) { this.namesAndValues = builder.namesAndValues.toArray(new String[builder.namesAndValues.size()]); } private Headers(String[] namesAndValues) { this.namesAndValues = namesAndValues; } /** Returns the last value corresponding to the specified field, or null. */ public String get(String name) { return get(namesAndValues, name); } /** * Returns the last value corresponding to the specified field parsed as an * HTTP date, or null if either the field is absent or cannot be parsed as a * date. */ public Date getDate(String name) { String value = get(name); return value != null ? HttpDate.parse(value) : null; } /** Returns the number of field values. */ public int size() { return namesAndValues.length / 2; } /** Returns the field at {@code position} or null if that is out of range. */ public String name(int index) { int nameIndex = index * 2; if (nameIndex < 0 || nameIndex >= namesAndValues.length) { return null; } return namesAndValues[nameIndex]; } /** Returns the value at {@code index} or null if that is out of range. */ public String value(int index) { int valueIndex = index * 2 + 1; if (valueIndex < 0 || valueIndex >= namesAndValues.length) { return null; } return namesAndValues[valueIndex]; } /** Returns an immutable case-insensitive set of header names. */ public Set<String> names() { TreeSet<String> result = new TreeSet<>(String.CASE_INSENSITIVE_ORDER); for (int i = 0, size = size(); i < size; i++) { result.add(name(i)); } return Collections.unmodifiableSet(result); } /** Returns an immutable list of the header values for {@code name}. */ public List<String> values(String name) { List<String> result = null; for (int i = 0, size = size(); i < size; i++) { if (name.equalsIgnoreCase(name(i))) { if (result == null) result = new ArrayList<>(2); result.add(value(i)); } } return result != null ? Collections.unmodifiableList(result) : Collections.<String>emptyList(); } public Builder newBuilder() { Builder result = new Builder(); Collections.addAll(result.namesAndValues, namesAndValues); return result; } @Override public String toString() { StringBuilder result = new StringBuilder(); for (int i = 0, size = size(); i < size; i++) { result.append(name(i)).append(": ").append(value(i)).append("\n"); } return result.toString(); } public Map<String, List<String>> toMultimap() { Map<String, List<String>> result = new LinkedHashMap<String, List<String>>(); for (int i = 0, size = size(); i < size; i++) { String name = name(i); List<String> values = result.get(name); if (values == null) { values = new ArrayList<>(2); result.put(name, values); } values.add(value(i)); } return result; } private static String get(String[] namesAndValues, String name) { for (int i = namesAndValues.length - 2; i >= 0; i -= 2) { if (name.equalsIgnoreCase(namesAndValues[i])) { return namesAndValues[i + 1]; } } return null; } /** * Returns headers for the alternating header names and values. There must be * an even number of arguments, and they must alternate between header names * and values. */ public static Headers of(String... namesAndValues) { if (namesAndValues == null || namesAndValues.length % 2 != 0) { throw new IllegalArgumentException("Expected alternating header names and values"); } // Make a defensive copy and clean it up. namesAndValues = namesAndValues.clone(); for (int i = 0; i < namesAndValues.length; i++) { if (namesAndValues[i] == null) throw new IllegalArgumentException("Headers cannot be null"); namesAndValues[i] = namesAndValues[i].trim(); } // Check for malformed headers. for (int i = 0; i < namesAndValues.length; i += 2) { String name = namesAndValues[i]; String value = namesAndValues[i + 1]; if (name.length() == 0 || name.indexOf('\0') != -1 || value.indexOf('\0') != -1) { throw new IllegalArgumentException("Unexpected header: " + name + ": " + value); } } return new Headers(namesAndValues); } /** * Returns headers for the header names and values in the {@link Map}. */ public static Headers of(Map<String, String> headers) { if (headers == null) { throw new IllegalArgumentException("Expected map with header names and values"); } // Make a defensive copy and clean it up. String[] namesAndValues = new String[headers.size() * 2]; int i = 0; for (Map.Entry<String, String> header : headers.entrySet()) { if (header.getKey() == null || header.getValue() == null) { throw new IllegalArgumentException("Headers cannot be null"); } String name = header.getKey().trim(); String value = header.getValue().trim(); if (name.length() == 0 || name.indexOf('\0') != -1 || value.indexOf('\0') != -1) { throw new IllegalArgumentException("Unexpected header: " + name + ": " + value); } namesAndValues[i] = name; namesAndValues[i + 1] = value; i += 2; } return new Headers(namesAndValues); } public static final class Builder { private final List<String> namesAndValues = new ArrayList<>(20); /** * Add a header line without any validation. Only appropriate for headers from the remote peer * or cache. */ Builder addLenient(String line) { int index = line.indexOf(":", 1); if (index != -1) { return addLenient(line.substring(0, index), line.substring(index + 1)); } else if (line.startsWith(":")) { // Work around empty header names and header names that start with a // colon (created by old broken SPDY versions of the response cache). return addLenient("", line.substring(1)); // Empty header name. } else { return addLenient("", line); // No header name. } } /** Add an header line containing a field name, a literal colon, and a value. */ public Builder add(String line) { int index = line.indexOf(":"); if (index == -1) { throw new IllegalArgumentException("Unexpected header: " + line); } return add(line.substring(0, index).trim(), line.substring(index + 1)); } /** Add a field with the specified value. */ public Builder add(String name, String value) { checkNameAndValue(name, value); return addLenient(name, value); } /** * Add a field with the specified value without any validation. Only * appropriate for headers from the remote peer or cache. */ Builder addLenient(String name, String value) { namesAndValues.add(name); namesAndValues.add(value.trim()); return this; } public Builder removeAll(String name) { for (int i = 0; i < namesAndValues.size(); i += 2) { if (name.equalsIgnoreCase(namesAndValues.get(i))) { namesAndValues.remove(i); // name namesAndValues.remove(i); // value i -= 2; } } return this; } /** * Set a field with the specified value. If the field is not found, it is * added. If the field is found, the existing values are replaced. */ public Builder set(String name, String value) { checkNameAndValue(name, value); removeAll(name); addLenient(name, value); return this; } private void checkNameAndValue(String name, String value) { if (name == null) throw new IllegalArgumentException("name == null"); if (name.isEmpty()) throw new IllegalArgumentException("name is empty"); for (int i = 0, length = name.length(); i < length; i++) { char c = name.charAt(i); if (c <= '\u001f' || c >= '\u007f') { throw new IllegalArgumentException( String.format("Unexpected char %#04x at %d in header name: %s", (int) c, i, name)); } } if (value == null) throw new IllegalArgumentException("value == null"); for (int i = 0, length = value.length(); i < length; i++) { char c = value.charAt(i); if (c <= '\u001f' || c >= '\u007f') { throw new IllegalArgumentException( String.format("Unexpected char %#04x at %d in header value: %s", (int) c, i, value)); } } } /** Equivalent to {@code build().get(name)}, but potentially faster. */ public String get(String name) { for (int i = namesAndValues.size() - 2; i >= 0; i -= 2) { if (name.equalsIgnoreCase(namesAndValues.get(i))) { return namesAndValues.get(i + 1); } } return null; } public Headers build() { return new Headers(this); } } }