// ***************************************************************************************************************************
// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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// * 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  *
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// * specific language governing permissions and limitations under the License.                                              *
// ***************************************************************************************************************************
package org.apache.juneau.rest;

import static org.apache.juneau.internal.ArrayUtils.*;
import static org.apache.juneau.internal.StringUtils.*;

import java.lang.reflect.*;
import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.http.*;
import org.apache.juneau.http.Date;
import org.apache.juneau.httppart.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.json.*;
import org.apache.juneau.oapi.*;
import org.apache.juneau.parser.*;
import org.apache.juneau.http.exception.*;

/**
 * Represents the headers in an HTTP request.
 *
 * <p>
 * Entries are stored in a case-insensitive map.
 *
 * <ul class='seealso'>
 *    <li class='link'>{@doc juneau-rest-server.RestMethod.RequestHeaders}
 * </ul>
 */
public class RequestHeaders extends TreeMap<String,String[]> {
   private static final long serialVersionUID = 1L;

   private final RestRequest req;
   private HttpPartParser parser;
   private RequestQuery queryParams;
   private Set<String> allowedQueryParams;

   RequestHeaders(RestRequest req) {
      super(String.CASE_INSENSITIVE_ORDER);
      this.req = req;
   }

   RequestHeaders parser(HttpPartParser parser) {
      this.parser = parser;
      return this;
   }

   RequestHeaders queryParams(RequestQuery queryParams, Set<String> allowedQueryParams) {
      this.queryParams = queryParams;
      this.allowedQueryParams = allowedQueryParams;
      return this;
   }

   /**
    * Adds default entries to these headers.
    *
    * <p>
    * Similar to {@link #put(String, Object)} but doesn't override existing values.
    *
    * @param defaultEntries
    *    The default entries.
    *    <br>Can be <jk>null</jk>.
    * @return This object (for method chaining).
    */
   public RequestHeaders addDefault(Map<String,Object> defaultEntries) {
      if (defaultEntries != null) {
         for (Map.Entry<String,Object> e : defaultEntries.entrySet()) {
            String key = e.getKey();
            Object value = e.getValue();
            String[] v = get(key);
            if (v == null || v.length == 0 || StringUtils.isEmpty(v[0]))
               put(key, stringifyAll(value));
         }
      }
      return this;
   }

   /**
    * Adds a default header value on this request.
    *
    * <p>
    * Similar to {@link #put(String, Object)} but doesn't override existing values.
    *
    * @param name
    *    The header name.
    * @param value
    *    The header value.
    *    <br>Converted to a String using <c>toString()</c>.
    *    <br>Ignored if value is <jk>null</jk> or blank.
    * @return This object (for method chaining).
    */
   public RequestHeaders addDefault(String name, Object value) {
      return addDefault(Collections.singletonMap(name, value));
   }

   /**
    * Adds a set of header values to this object.
    *
    * @param name The header name.
    * @param values The header values.
    * @return This object (for method chaining).
    */
   public RequestHeaders put(String name, Enumeration<String> values) {
      // Optimized for enumerations of one entry, the most-common case.
      if (values.hasMoreElements()) {
         String v = values.nextElement();
         String[] s = new String[]{v};
         while (values.hasMoreElements())
            s = append(s, values.nextElement());
         put(name, s);
      }
      return this;
   }

   /**
    * Returns the specified header value as a string.
    *
    * <ul class='notes'>
    *    <li>
    *       If {@code allowHeaderParams} init parameter is <jk>true</jk>, then first looks for {@code &HeaderName=x} in the URL query string.
    * </ul>
    *
    * @param name The header name.
    * @return The header value, or <jk>null</jk> if it doesn't exist.
    */
   public String getString(String name) {
      String[] v = null;
      if (queryParams != null)
         if (allowedQueryParams.contains("*") || allowedQueryParams.contains(name))
            v = queryParams.get(name, true);
      if (v == null || v.length == 0)
         v = get(name);
      if (v == null || v.length == 0)
         return null;
      return v[0];
   }

   /**
    * Returns the specified header value as a string.
    *
    * <ul class='notes'>
    *    <li>
    *       If {@code allowHeaderParams} init parameter is <jk>true</jk>, then first looks for {@code &HeaderName=x} in the URL query string.
    * </ul>
    *
    * @param name The HTTP header name.
    * @param def The default value to return if the header value isn't found.
    * @return The header value, or the default value if the header isn't present.
    */
   public String getString(String name, String def) {
      String s = getString(name);
      return StringUtils.isEmpty(s) ? def : s;
   }

   /**
    * Same as {@link #getString(String)} but converts the value to an integer.
    *
    * @param name The HTTP header name.
    * @return The header value, or the default value if the header isn't present.
    */
   public int getInt(String name) {
      return getInt(name, 0);
   }

   /**
    * Same as {@link #getString(String,String)} but converts the value to an integer.
    *
    * @param name The HTTP header name.
    * @param def The default value to return if the header value isn't found.
    * @return The header value, or the default value if the header isn't present.
    */
   public int getInt(String name, int def) {
      String s = getString(name);
      return StringUtils.isEmpty(s) ? def : Integer.parseInt(s);
   }

   /**
    * Same as {@link #getString(String)} but converts the value to a boolean.
    *
    * @param name The HTTP header name.
    * @return The header value, or the default value if the header isn't present.
    */
   public boolean getBoolean(String name) {
      return getBoolean(name, false);
   }

   /**
    * Same as {@link #getString(String,String)} but converts the value to a boolean.
    *
    * @param name The HTTP header name.
    * @param def The default value to return if the header value isn't found.
    * @return The header value, or the default value if the header isn't present.
    */
   public boolean getBoolean(String name, boolean def) {
      String s = getString(name);
      return StringUtils.isEmpty(s) ? def : Boolean.parseBoolean(s);
   }

   /**
    * Sets a request header value.
    *
    * <p>
    * This overwrites any previous value.
    *
    * @param name The header name.
    * @param value The header value.
    */
   public void put(String name, Object value) {
      super.put(name, stringifyAll(value));
   }

   /**
    * Returns the specified header value converted to a POJO using the {@link HttpPartParser} registered with the resource.
    *
    * <h5 class='section'>Examples:</h5>
    * <p class='bcode w800'>
    *    <jc>// Parse into an integer.</jc>
    *    <jk>int</jk> myheader = req.getHeader(<js>"My-Header"</js>, <jk>int</jk>.<jk>class</jk>);
    *
    *    <jc>// Parse a UUID.</jc>
    *    UUID myheader = req.getHeader(<js>"My-Header"</js>, UUID.<jk>class</jk>);
    * </p>
    *
    * <ul class='notes'>
    *    <li>
    *       If {@code allowHeaderParams} init parameter is <jk>true</jk>, then first looks for {@code &HeaderName=x} in the URL query string.
    * </ul>
    *
    * <ul class='seealso'>
    *    <li class='jf'>{@link RestContext#REST_partParser}
    * </ul>
    *
    * @param name The HTTP header name.
    * @param type The class type to convert the header value to.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(String name, Class<T> type) throws BadRequest, InternalServerError {
      return getInner(null, null, name, null, getClassMeta(type));
   }

   /**
    * Same as {@link #get(String, Class)} but allows you to override the part parser used.
    *
    * @param parser
    *    The parser to use for parsing the string header.
    *    <br>If <jk>null</jk>, uses the part parser defined on the resource/method.
    * @param schema
    *    The schema object that defines the format of the input.
    *    <br>If <jk>null</jk>, defaults to the schema defined on the parser.
    *    <br>If that's also <jk>null</jk>, defaults to {@link HttpPartSchema#DEFAULT}.
    *    <br>Only used if parser is schema-aware (e.g. {@link OpenApiParser}).
    * @param name The HTTP header name.
    * @param type The class type to convert the header value to.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed or fails schema validation.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(HttpPartParser parser, HttpPartSchema schema, String name, Class<T> type) throws BadRequest, InternalServerError {
      return getInner(parser, schema, name, null, getClassMeta(type));
   }

   /**
    * Same as {@link #get(String, Class)} but returns a default value if not found.
    *
    * @param name The HTTP header name.
    * @param def The default value if the header was not specified or is <jk>null</jk>.
    * @param type The class type to convert the header value to.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(String name, T def, Class<T> type) throws BadRequest, InternalServerError {
      return getInner(null, null, name, def, getClassMeta(type));
   }

   /**
    * Same as {@link #get(String, Object, Class)} but allows you to override the part parser used.
    *
    * @param parser
    *    The parser to use for parsing the string header.
    *    <br>If <jk>null</jk>, uses the part parser defined on the resource/method.
    * @param schema
    *    The schema object that defines the format of the input.
    *    <br>If <jk>null</jk>, defaults to the schema defined on the parser.
    *    <br>If that's also <jk>null</jk>, defaults to {@link HttpPartSchema#DEFAULT}.
    *    <br>Only used if parser is schema-aware (e.g. {@link OpenApiParser}).
    * @param name The HTTP header name.
    * @param def The default value if the header was not specified or is <jk>null</jk>.
    * @param type The class type to convert the header value to.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed or fails schema validation.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(HttpPartParser parser, HttpPartSchema schema, String name, T def, Class<T> type) throws BadRequest, InternalServerError {
      return getInner(parser, schema, name, def, getClassMeta(type));
   }

   /**
    * Returns the specified header value converted to a POJO using the {@link HttpPartParser} registered with the resource.
    *
    * <p>
    * Similar to {@link #get(String,Class)} but allows for complex collections of POJOs to be created.
    *
    * <h5 class='section'>Examples:</h5>
    * <p class='bcode w800'>
    *    <jc>// Parse into a linked-list of strings.</jc>
    *    List&lt;String&gt; myheader = req.getHeader(<js>"My-Header"</js>, LinkedList.<jk>class</jk>, String.<jk>class</jk>);
    * </p>
    *
    * <ul class='notes'>
    *    <li>
    *       <c>Collections</c> must be followed by zero or one parameter representing the value type.
    *    <li>
    *       <c>Maps</c> must be followed by zero or two parameters representing the key and value types.
    *    <li>
    *       If {@code allowHeaderParams} init parameter is <jk>true</jk>, then first looks for {@code &HeaderName=x} in the URL query string.
    * </ul>
    *
    * <ul class='seealso'>
    *    <li class='jf'>{@link RestContext#REST_partParser}
    * </ul>
    *
    * @param name The HTTP header name.
    * @param type
    *    The type of object to create.
    *    <br>Can be any of the following: {@link ClassMeta}, {@link Class}, {@link ParameterizedType}, {@link GenericArrayType}
    * @param args
    *    The type arguments of the class if it's a collection or map.
    *    <br>Can be any of the following: {@link ClassMeta}, {@link Class}, {@link ParameterizedType}, {@link GenericArrayType}
    *    <br>Ignored if the main type is not a map or collection.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(String name, Type type, Type...args) throws BadRequest, InternalServerError {
      return getInner(null, null, name, null, this.<T>getClassMeta(type, args));
   }

   /**
    * Same as {@link #get(String, Type, Type...)} but allows you to override the part parser used.
    *
    * @param parser
    *    The parser to use for parsing the string header.
    *    <br>If <jk>null</jk>, uses the part parser defined on the resource/method.
    * @param schema
    *    The schema object that defines the format of the input.
    *    <br>If <jk>null</jk>, defaults to the schema defined on the parser.
    *    <br>If that's also <jk>null</jk>, defaults to {@link HttpPartSchema#DEFAULT}.
    *    <br>Only used if parser is schema-aware (e.g. {@link OpenApiParser}).
    * @param name
    *    The HTTP header name.
    * @param type
    *    The type of object to create.
    *    <br>Can be any of the following: {@link ClassMeta}, {@link Class}, {@link ParameterizedType}, {@link GenericArrayType}
    * @param args
    *    The type arguments of the class if it's a collection or map.
    *    <br>Can be any of the following: {@link ClassMeta}, {@link Class}, {@link ParameterizedType}, {@link GenericArrayType}
    *    <br>Ignored if the main type is not a map or collection.
    * @param <T> The class type to convert the header value to.
    * @return The parameter value converted to the specified class type.
    * @throws BadRequest Thrown if input could not be parsed or fails schema validation.
    * @throws InternalServerError Thrown if any other exception occurs.
    */
   public <T> T get(HttpPartParser parser, HttpPartSchema schema, String name, Type type, Type...args) throws BadRequest, InternalServerError {
      return getInner(parser, schema, name, null, this.<T>getClassMeta(type, args));
   }

   /* Workhorse method */
   private <T> T getInner(HttpPartParser parser, HttpPartSchema schema, String name, T def, ClassMeta<T> cm) throws BadRequest, InternalServerError {
      try {
         if (cm.isMapOrBean() && isOneOf(name, "*", "")) {
            ObjectMap m = new ObjectMap();
            for (Map.Entry<String,String[]> e : this.entrySet()) {
               String k = e.getKey();
               HttpPartSchema pschema = schema == null ? null : schema.getProperty(k);
               ClassMeta<?> cm2 = cm.getValueType();
               m.put(k, getInner(parser, pschema, k, null, cm2));
            }
            return req.getBeanSession().convertToType(m, cm);
         }
         T t = parse(parser, schema, getString(name), cm);
         return (t == null ? def : t);
      } catch (SchemaValidationException e) {
         throw new BadRequest(e, "Validation failed on header ''{0}''. ", name);
      } catch (ParseException e) {
         throw new BadRequest(e, "Could not parse header ''{0}''.", name) ;
      } catch (Exception e) {
         throw new InternalServerError(e, "Could not parse header ''{0}''.", name);
      }
   }

   /* Workhorse method */
   private <T> T parse(HttpPartParser parser, HttpPartSchema schema, String val, ClassMeta<T> cm) throws SchemaValidationException, ParseException {
      if (parser == null)
         parser = this.parser;
      return parser.createPartSession(req.getParserSessionArgs()).parse(HttpPartType.HEADER, schema, val, cm);
   }

   /**
    * Returns a copy of this object but only with the specified header names copied.
    *
    * @param headers The headers to include in the copy.
    * @return A new headers object.
    */
   public RequestHeaders subset(String...headers) {
      RequestHeaders rh2 = new RequestHeaders(req).parser(parser).queryParams(queryParams, allowedQueryParams);
      for (String h : headers)
         if (containsKey(h))
            rh2.put(h, get(h));
      return rh2;
   }

   /**
    * Same as {@link #subset(String...)} but allows you to specify header names as a comma-delimited list.
    *
    * @param headers The headers to include in the copy.
    * @return A new headers object.
    */
   public RequestHeaders subset(String headers) {
      return subset(split(headers));
   }

   /**
    * Returns the <c>Accept</c> header on the request.
    *
    * <p>
    * Content-Types that are acceptable for the response.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Accept: text/plain
    * </p>
    *
    * @return The parsed <c>Accept</c> header on the request, or <jk>null</jk> if not found.
    */
   public Accept getAccept() {
      return Accept.forString(getString("Accept"));
   }

   /**
    * Returns the <c>Accept-Charset</c> header on the request.
    *
    * <p>
    * Character sets that are acceptable.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Accept-Charset: utf-8
    * </p>
    *
    * @return The parsed <c>Accept-Charset</c> header on the request, or <jk>null</jk> if not found.
    */
   public AcceptCharset getAcceptCharset() {
      return AcceptCharset.forString(getString("Accept-Charset"));
   }

   /**
    * Returns the <c>Accept-Encoding</c> header on the request.
    *
    * <p>
    * List of acceptable encodings.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Accept-Encoding: gzip, deflate
    * </p>
    *
    * @return The parsed <c>Accept-Encoding</c> header on the request, or <jk>null</jk> if not found.
    */
   public AcceptEncoding getAcceptEncoding() {
      return AcceptEncoding.forString(getString("Accept-Encoding"));
   }

   /**
    * Returns the <c>Accept-Language</c> header on the request.
    *
    * <p>
    * List of acceptable human languages for response.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Accept-Language: en-US
    * </p>
    *
    * @return The parsed <c>Accept-Language</c> header on the request, or <jk>null</jk> if not found.
    */
   public AcceptLanguage getAcceptLanguage() {
      return AcceptLanguage.forString(getString("Accept-Language"));
   }

   /**
    * Returns the <c>Authorization</c> header on the request.
    *
    * <p>
    * Authentication credentials for HTTP authentication.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
    * </p>
    *
    * @return The parsed <c>Authorization</c> header on the request, or <jk>null</jk> if not found.
    */
   public Authorization getAuthorization() {
      return Authorization.forString(getString("Authorization"));
   }

   /**
    * Returns the <c>Cache-Control</c> header on the request.
    *
    * <p>
    * Used to specify directives that must be obeyed by all caching mechanisms along the request-response chain.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Cache-Control: no-cache
    * </p>
    *
    * @return The parsed <c>Cache-Control</c> header on the request, or <jk>null</jk> if not found.
    */
   public CacheControl getCacheControl() {
      return CacheControl.forString(getString("Cache-Control"));
   }

   /**
    * Returns the <c>Connection</c> header on the request.
    *
    * <p>
    * Control options for the current connection and list of hop-by-hop request fields.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Connection: keep-alive
    *    Connection: Upgrade
    * </p>
    *
    * @return The parsed <code></code> header on the request, or <jk>null</jk> if not found.
    */
   public Connection getConnection() {
      return Connection.forString(getString("Connection"));
   }

   /**
    * Returns the <c>Content-Length</c> header on the request.
    *
    * <p>
    * The length of the request body in octets (8-bit bytes).
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Content-Length: 348
    * </p>
    *
    * @return The parsed <c>Content-Length</c> header on the request, or <jk>null</jk> if not found.
    */
   public ContentLength getContentLength() {
      return ContentLength.forString(getString("Content-Length"));
   }

   /**
    * Returns the <c>Content-Type</c> header on the request.
    *
    * <p>
    * The MIME type of the body of the request (used with POST and PUT requests).
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Content-Type: application/x-www-form-urlencoded
    * </p>
    *
    * @return The parsed <c>Content-Type</c> header on the request, or <jk>null</jk> if not found.
    */
   public ContentType getContentType() {
      return ContentType.forString(getString("Content-Type"));
   }

   /**
    * Returns the <c>Date</c> header on the request.
    *
    * <p>
    * The date and time that the message was originated (in "HTTP-date" format as defined by RFC 7231 Date/Time Formats).
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Date: Tue, 15 Nov 1994 08:12:31 GMT
    * </p>
    *
    * @return The parsed <c>Date</c> header on the request, or <jk>null</jk> if not found.
    */
   public Date getDate() {
      return Date.forString(getString("Date"));
   }

   /**
    * Returns the <c>Expect</c> header on the request.
    *
    * <p>
    * Indicates that particular server behaviors are required by the client.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Expect: 100-continue
    * </p>
    *
    * @return The parsed <c>Expect</c> header on the request, or <jk>null</jk> if not found.
    */
   public Expect getExpect() {
      return Expect.forString(getString("Expect"));
   }

   /**
    * Returns the <c>From</c> header on the request.
    *
    * <p>
    * The email address of the user making the request.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    From: user@example.com
    * </p>
    *
    * @return The parsed <c>From</c> header on the request, or <jk>null</jk> if not found.
    */
   public From getFrom() {
      return From.forString(getString("From"));
   }

   /**
    * Returns the <c>Host</c> header on the request.
    *
    * <p>
    * The domain name of the server (for virtual hosting), and the TCP port number on which the server is listening.
    * The port number may be omitted if the port is the standard port for the service requested.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Host: en.wikipedia.org:8080
    *    Host: en.wikipedia.org
    * </p>
    *
    * @return The parsed <c>Host</c> header on the request, or <jk>null</jk> if not found.
    */
   public Host getHost() {
      return Host.forString(getString("Host"));
   }

   /**
    * Returns the <c>If-Match</c> header on the request.
    *
    * <p>
    * Only perform the action if the client supplied entity matches the same entity on the server.
    * This is mainly for methods like PUT to only update a resource if it has not been modified since the user last
    * updated it.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    If-Match: "737060cd8c284d8af7ad3082f209582d"
    * </p>
    *
    * @return The parsed <c>If-Match</c> header on the request, or <jk>null</jk> if not found.
    */
   public IfMatch getIfMatch() {
      return IfMatch.forString(getString("If-Match"));
   }

   /**
    * Returns the <c>If-Modified-Since</c> header on the request.
    *
    * <p>
    * Allows a 304 Not Modified to be returned if content is unchanged.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
    * </p>
    *
    * @return The parsed <c>If-Modified-Since</c> header on the request, or <jk>null</jk> if not found.
    */
   public IfModifiedSince getIfModifiedSince() {
      return IfModifiedSince.forString(getString("If-Modified-Since"));
   }

   /**
    * Returns the <c>If-None-Match</c> header on the request.
    *
    * <p>
    * Allows a 304 Not Modified to be returned if content is unchanged, see HTTP ETag.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    If-None-Match: "737060cd8c284d8af7ad3082f209582d"
    * </p>
    *
    * @return The parsed <c>If-None-Match</c> header on the request, or <jk>null</jk> if not found.
    */
   public IfNoneMatch getIfNoneMatch() {
      return IfNoneMatch.forString(getString("If-None-Match"));
   }

   /**
    * Returns the <c>If-Range</c> header on the request.
    *
    * <p>
    * If the entity is unchanged, send me the part(s) that I am missing; otherwise, send me the entire new entity.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    If-Range: "737060cd8c284d8af7ad3082f209582d"
    * </p>
    *
    * @return The parsed <c>If-Range</c> header on the request, or <jk>null</jk> if not found.
    */
   public IfRange getIfRange() {
      return IfRange.forString(getString("If-Range"));
   }

   /**
    * Returns the <c>If-Unmodified-Since</c> header on the request.
    *
    * <p>
    * Only send the response if the entity has not been modified since a specific time.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT
    * </p>
    *
    * @return The parsed <c>If-Unmodified-Since</c> header on the request, or <jk>null</jk> if not found.
    */
   public IfUnmodifiedSince getIfUnmodifiedSince() {
      return IfUnmodifiedSince.forString(getString("If-Unmodified-Since"));
   }

   /**
    * Returns the <c>Max-Forwards</c> header on the request.
    *
    * <p>
    * Limit the number of times the message can be forwarded through proxies or gateways.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Max-Forwards: 10
    * </p>
    *
    * @return The parsed <c>Max-Forwards</c> header on the request, or <jk>null</jk> if not found.
    */
   public MaxForwards getMaxForwards() {
      return MaxForwards.forString(getString("Max-Forwards"));
   }

   /**
    * Returns the <c>Pragma</c> header on the request.
    *
    * <p>
    * Implementation-specific fields that may have various effects anywhere along the request-response chain.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Pragma: no-cache
    * </p>
    *
    * @return The parsed <c>Pragma</c> header on the request, or <jk>null</jk> if not found.
    */
   public Pragma getPragma() {
      return Pragma.forString(getString("Pragma"));
   }

   /**
    * Returns the <c>Proxy-Authorization</c> header on the request.
    *
    * <p>
    * Authorization credentials for connecting to a proxy.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Proxy-Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
    * </p>
    *
    * @return The parsed <c>Proxy-Authorization</c> header on the request, or <jk>null</jk> if not found.
    */
   public ProxyAuthorization getProxyAuthorization() {
      return ProxyAuthorization.forString(getString("Proxy-Authorization"));
   }

   /**
    * Returns the <c>Range</c> header on the request.
    *
    * <p>
    * Request only part of an entity. Bytes are numbered from 0.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Range: bytes=500-999
    * </p>
    *
    * @return The parsed <c>Range</c> header on the request, or <jk>null</jk> if not found.
    */
   public Range getRange() {
      return Range.forString(getString("Range"));
   }

   /**
    * Returns the <c>Referer</c> header on the request.
    *
    * <p>
    * This is the address of the previous web page from which a link to the currently requested page was followed.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Referer: http://en.wikipedia.org/wiki/Main_Page
    * </p>
    *
    * @return The parsed <c>Referer</c> header on the request, or <jk>null</jk> if not found.
    */
   public Referer getReferer() {
      return Referer.forString(getString("Referer"));
   }

   /**
    * Returns the <c>TE</c> header on the request.
    *
    * <p>
    * The transfer encodings the user agent is willing to accept: the same values as for the response header field
    * Transfer-Encoding can be used, plus the "trailers" value (related to the "chunked" transfer method) to notify the
    * server it expects to receive additional fields in the trailer after the last, zero-sized, chunk.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    TE: trailers, deflate
    * </p>
    *
    * @return The parsed <c>TE</c> header on the request, or <jk>null</jk> if not found.
    */
   public TE getTE() {
      return TE.forString(getString("TE"));
   }

   /**
    * Returns the <c>Time-Zone</c> header value on the request if there is one.
    *
    * <p>
    * Example: <js>"GMT"</js>.
    *
    * @return The <c>Time-Zone</c> header value on the request, or <jk>null</jk> if not present.
    */
   public TimeZone getTimeZone() {
      String tz = getString("Time-Zone");
      if (tz != null)
         return TimeZone.getTimeZone(tz);
      return null;
   }

   /**
    * Returns the <c>User-Agent</c> header on the request.
    *
    * <p>
    * The user agent string of the user agent.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/21.0
    * </p>
    *
    * @return The parsed <c>User-Agent</c> header on the request, or <jk>null</jk> if not found.
    */
   public UserAgent getUserAgent() {
      return UserAgent.forString(getString("User-Agent"));
   }

   /**
    * Returns the <c>Upgrade</c> header on the request.
    *
    * <p>
    * Ask the server to upgrade to another protocol.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Upgrade: HTTP/2.0, HTTPS/1.3, IRC/6.9, RTA/x11, websocket
    * </p>
    *
    * @return The parsed <c>Upgrade</c> header on the request, or <jk>null</jk> if not found.
    */
   public Upgrade getUpgrade() {
      return Upgrade.forString(getString("Upgrade"));
   }

   /**
    * Returns the <c>Via</c> header on the request.
    *
    * <p>
    * Informs the server of proxies through which the request was sent.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Via: 1.0 fred, 1.1 example.com (Apache/1.1)
    * </p>
    *
    * @return The parsed <c>Via</c> header on the request, or <jk>null</jk> if not found.
    */
   public Via getVia() {
      return Via.forString(getString("Via"));
   }

   /**
    * Returns the <c>Warning</c> header on the request.
    *
    * <p>
    * A general warning about possible problems with the entity body.
    *
    * <h5 class='figure'>Example:</h5>
    * <p class='bcode w800'>
    *    Warning: 199 Miscellaneous warning
    * </p>
    *
    * @return The parsed <c>Warning</c> header on the request, or <jk>null</jk> if not found.
    */
   public Warning getWarning() {
      return Warning.forString(getString("Warning"));
   }

   /**
    * Converts the headers to a readable string.
    *
    * @param sorted Sort the headers by name.
    * @return A JSON string containing the contents of the headers.
    */
   public String toString(boolean sorted) {
      Map<String,Object> m = null;
      if (sorted)
         m = new TreeMap<>();
      else
         m = new LinkedHashMap<>();
      for (Map.Entry<String,String[]> e : this.entrySet()) {
         String[] v = e.getValue();
         m.put(e.getKey(), v.length == 1 ? v[0] : v);
      }
      return SimpleJsonSerializer.DEFAULT.toString(m);
   }

   @Override /* Object */
   public String toString() {
      return toString(false);
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Helper methods
   //-----------------------------------------------------------------------------------------------------------------

   private <T> ClassMeta<T> getClassMeta(Type type, Type...args) {
      return req.getBeanSession().getClassMeta(type, args);
   }

   private <T> ClassMeta<T> getClassMeta(Class<T> type) {
      return req.getBeanSession().getClassMeta(type);
   }
}