// ***************************************************************************************************************************
// * 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  *
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// * specific language governing permissions and limitations under the License.                                              *
// ***************************************************************************************************************************
package org.apache.juneau.rest;

import static org.apache.juneau.internal.StringUtils.*;
import static org.apache.juneau.httppart.HttpPartType.*;

import java.io.*;
import java.nio.charset.*;
import java.util.*;

import javax.servlet.*;
import javax.servlet.http.*;

import org.apache.http.*;
import org.apache.juneau.*;
import org.apache.juneau.collections.*;
import org.apache.juneau.encoders.*;
import org.apache.juneau.html.annotation.*;
import org.apache.juneau.http.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.httppart.bean.*;
import org.apache.juneau.rest.annotation.*;
import org.apache.juneau.http.exception.*;
import org.apache.juneau.http.header.*;
import org.apache.juneau.rest.util.*;
import org.apache.juneau.serializer.*;

/**
 * Represents an HTTP response for a REST resource.
 *
 * <p>
 * Essentially an extended {@link HttpServletResponse} with some special convenience methods that allow you to easily
 * output POJOs as responses.
 *
 * <p>
 * Since this class extends {@link HttpServletResponse}, developers are free to use these convenience methods, or
 * revert to using lower level methods like any other servlet response.
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bcode w800'>
 *    <ja>@RestMethod</ja>(name=<jsf>GET</jsf>)
 *    <jk>public void</jk> doGet(RestRequest req, RestResponse res) {
 *       res.setOutput(<js>"Simple string response"</js>);
 *    }
 * </p>
 *
 * <ul class='seealso'>
 *    <li class='link'>{@doc RestmRestResponse}
 * </ul>
 */
public final class RestResponse extends HttpServletResponseWrapper {

   private HttpServletResponse inner;
   private final RestRequest request;
   private RestMethodContext restJavaMethod;
   private Object output;                       // The POJO being sent to the output.
   private boolean isNullOutput;                // The output is null (as opposed to not being set at all)
   @SuppressWarnings("deprecation")
   private RequestProperties properties;                // Response properties
   private ServletOutputStream sos;
   private FinishableServletOutputStream os;
   private FinishablePrintWriter w;
   @SuppressWarnings("deprecation")
   private HtmlDocBuilder htmlDocBuilder;

   private ResponseBeanMeta responseMeta;

   /**
    * Constructor.
    */
   RestResponse(RestCall call) throws BadRequest {
      super(call.getResponse());
      this.inner = call.getResponse();
      this.request = call.getRestRequest();
      call.restResponse(this);
      RestContext context = call.getContext();

      for (Map.Entry<String,Object> e : context.getResHeaders().entrySet())
         setHeaderSafe(e.getKey(), stringify(e.getValue()));

      try {
         String passThroughHeaders = request.getHeader("x-response-headers");
         if (passThroughHeaders != null) {
            HttpPartParser p = context.getPartParser();
            OMap m = p.createPartSession(request.getParserSessionArgs()).parse(HEADER, null, passThroughHeaders, context.getClassMeta(OMap.class));
            for (Map.Entry<String,Object> e : m.entrySet())
               setHeaderSafe(e.getKey(), e.getValue().toString());
         }
      } catch (Exception e1) {
         throw new BadRequest(e1, "Invalid format for header 'x-response-headers'.  Must be in URL-encoded format.");
      }
   }

   /*
    * Called from RestServlet after a match has been made but before the guard or method invocation.
    */
   final void init(RestMethodContext rjm, @SuppressWarnings("deprecation") RequestProperties properties) throws NotAcceptable, IOException {
      this.restJavaMethod = rjm;
      this.properties = properties;

      if (request.isDebug())
         setDebug();

      // Find acceptable charset
      String h = request.getHeader("accept-charset");
      String charset = null;
      if (h == null)
         charset = rjm.defaultCharset;
      else for (StringRange r : StringRanges.of(h).getRanges()) {
         if (r.getQValue() > 0) {
            if (r.getName().equals("*"))
               charset = rjm.defaultCharset;
            else if (Charset.isSupported(r.getName()))
               charset = r.getName();
            if (charset != null)
               break;
         }
      }

      if (charset == null)
         throw new NotAcceptable("No supported charsets in header ''Accept-Charset'': ''{0}''", request.getHeader("Accept-Charset"));
      super.setCharacterEncoding(charset);

      this.responseMeta = rjm.responseMeta;
   }

   /**
    * Gets the serializer group for the response.
    *
    * <ul class='seealso'>
    *    <li class='link'>{@doc RestSerializers}
    * </ul>
    *
    * @return The serializer group for the response.
    */
   public SerializerGroup getSerializers() {
      return restJavaMethod == null ? SerializerGroup.EMPTY : restJavaMethod.serializers;
   }

   /**
    * Returns the media types that are valid for <c>Accept</c> headers on the request.
    *
    * @return The set of media types registered in the parser group of this request.
    */
   public List<MediaType> getSupportedMediaTypes() {
      return restJavaMethod == null ? Collections.<MediaType>emptyList() : restJavaMethod.supportedAcceptTypes;
   }

   /**
    * Returns the codings that are valid for <c>Accept-Encoding</c> and <c>Content-Encoding</c> headers on
    * the request.
    *
    * @return The set of media types registered in the parser group of this request.
    */
   public List<String> getSupportedEncodings() {
      return restJavaMethod == null ? Collections.<String>emptyList() : restJavaMethod.encoders.getSupportedEncodings();
   }

   /**
    * Sets the HTTP output on the response.
    *
    * <p>
    * The object type can be anything allowed by the registered response handlers.
    *
    * <p>
    * Calling this method is functionally equivalent to returning the object in the REST Java method.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bcode w800'>
    *    <ja>@RestMethod</ja>(..., path=<js>"/example2/{personId}"</js>)
    *    <jk>public void</jk> doGet2(RestResponse res, <ja>@Path</ja> UUID personId) {
    *       Person p = getPersonById(personId);
    *       res.setOutput(p);
    *    }
    * </p>
    *
    * <ul class='notes'>
    *    <li>
    *       Calling this method with a <jk>null</jk> value is NOT the same as not calling this method at all.
    *       <br>A <jk>null</jk> output value means we want to serialize <jk>null</jk> as a response (e.g. as a JSON <c>null</c>).
    *       <br>Not calling this method or returning a value means you're handing the response yourself via the underlying stream or writer.
    *       <br>This distinction affects the {@link #hasOutput()} method behavior.
    * </ul>
    *
    * <ul class='seealso'>
    *    <li class='jf'>{@link RestContext#REST_responseHandlers}
    *    <li class='link'>{@doc RestmReturnTypes}
    * </ul>
    *
    * @param output The output to serialize to the connection.
    * @return This object (for method chaining).
    */
   public RestResponse setOutput(Object output) {
      this.output = output;
      this.isNullOutput = output == null;
      return this;
   }

   /**
    * Returns a programmatic interface for setting properties for the HTML doc view.
    *
    * <div class='warn'>
    *    <b>Deprecated</b> - Use {@link HtmlDocConfig}
    * </div>
    *
    * <p>
    * This is the programmatic equivalent to the {@link RestMethod#htmldoc() @RestMethod(htmldoc)} annotation.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bcode w800'>
    *    <jc>// Declarative approach.</jc>
    *  <ja>@HtmlDocConfig</ja>(
    *       header={
    *          <js>"&lt;p&gt;This is my REST interface&lt;/p&gt;"</js>
    *       },
    *       aside={
    *          <js>"&lt;p&gt;Custom aside content&lt;/p&gt;"</js>
    *       }
    *    )
    *    <jk>public</jk> Object doGet(RestResponse res) {
    *
    *       <jc>// Equivalent programmatic approach.</jc>
    *       res.getHtmlDocBuilder()
    *          .header(<js>"&lt;p&gt;This is my REST interface&lt;/p&gt;"</js>)
    *          .aside(<js>"&lt;p&gt;Custom aside content&lt;/p&gt;"</js>);
    *    }
    * </p>
    *
    * <ul class='seealso'>
    *    <li class='ja'>{@link RestMethod#htmldoc()}
    *    <li class='link'>{@doc RestHtmlDocAnnotation}
    * </ul>
    *
    * @return A new programmatic interface for setting properties for the HTML doc view.
    */
   @Deprecated
   public HtmlDocBuilder getHtmlDocBuilder() {
      if (htmlDocBuilder == null)
         htmlDocBuilder = new HtmlDocBuilder(PropertyStore.create());
      return htmlDocBuilder;
   }

   /**
    * Retrieve the properties active for this request.
    *
    * <div class='warn'>
    *    <b>Deprecated</b> - Use {@link RestResponse#getAttributes()}
    * </div>
    *
    * <p>
    * This contains all resource and method level properties from the following:
    * <ul class='javatree'>
    *    <li class='ja'>{@link Rest#properties()}
    *    <li class='ja'>{@link RestMethod#properties()}
    *    <li class='jm'>{@link RestContextBuilder#set(String, Object)}
    * </ul>
    *
    * <p>
    * The returned object is modifiable and allows you to override session-level properties before
    * they get passed to the serializers.
    * <br>However, properties are open-ended, and can be used for any purpose.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bcode w800'>
    *    <ja>@RestMethod</ja>(
    *       properties={
    *          <ja>@Property</ja>(name=<jsf>SERIALIZER_sortMaps</jsf>, value=<js>"false"</js>)
    *       }
    *    )
    *    <jk>public</jk> Map doGet(RestResponse res, <ja>@Query</ja>(<js>"sortMaps"</js>) Boolean sortMaps) {
    *
    *       <jc>// Override value if specified through query parameter.</jc>
    *       <jk>if</jk> (sortMaps != <jk>null</jk>)
    *          res.getProperties().put(<jsf>SERIALIZER_sortMaps</jsf>, sortMaps);
    *
    *       <jk>return</jk> <jsm>getMyMap</jsm>();
    *    }
    * </p>
    *
    * <ul class='seealso'>
    *    <li class='jm'>{@link #prop(String, Object)}
    *    <li class='link'>{@doc RestConfigurableProperties}
    * </ul>
    *
    * @return The properties active for this request.
    */
   @Deprecated
   public RequestProperties getProperties() {
      return properties;
   }

   /**
    * Shortcut for calling <c>getProperties().append(name, value);</c> fluently.
    *
    * <div class='warn'>
    *    <b>Deprecated</b> - Use {@link #attr(String,Object)}
    * </div>
    *
    * @param name The property name.
    * @param value The property value.
    * @return This object (for method chaining).
    */
   @Deprecated
   public RestResponse prop(String name, Object value) {
      this.properties.append(name, value);
      return this;
   }

   /**
    * Shortcut for calling <c>getRequest().getAttributes()</c>.
    *
    * @return The request attributes object.
    */
   public RequestAttributes getAttributes() {
      return request.getAttributes();
   }

   /**
    * Shortcut for calling <c>getRequest().setAttribute(String,Object)</c>.
    *
    * @param name The property name.
    * @param value The property value.
    * @return This object (for method chaining).
    */
   public RestResponse attr(String name, Object value) {
      request.setAttribute(name, value);
      return this;
   }

   /**
    * Shortcut method that allows you to use var-args to simplify setting array output.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bcode w800'>
    *    <jc>// Instead of...</jc>
    *    response.setOutput(<jk>new</jk> Object[]{x,y,z});
    *
    *    <jc>// ...call this...</jc>
    *    response.setOutput(x,y,z);
    * </p>
    *
    * @param output The output to serialize to the connection.
    * @return This object (for method chaining).
    */
   public RestResponse setOutputs(Object...output) {
      this.output = output;
      return this;
   }

   /**
    * Returns the output that was set by calling {@link #setOutput(Object)}.
    *
    * @return The output object.
    */
   public Object getOutput() {
      return output;
   }

   /**
    * Returns <jk>true</jk> if this response has any output associated with it.
    *
    * @return <jk>true</jk> if {@link #setOutput(Object)} has been called, even if the value passed was <jk>null</jk>.
    */
   public boolean hasOutput() {
      return output != null || isNullOutput;
   }

   /**
    * Sets the output to a plain-text message regardless of the content type.
    *
    * @param text The output text to send.
    * @return This object (for method chaining).
    * @throws IOException If a problem occurred trying to write to the writer.
    */
   public RestResponse sendPlainText(String text) throws IOException {
      setContentType("text/plain");
      getNegotiatedWriter().write(text);
      return this;
   }

   /**
    * Equivalent to {@link HttpServletResponse#getOutputStream()}, except wraps the output stream if an {@link Encoder}
    * was found that matched the <c>Accept-Encoding</c> header.
    *
    * @return A negotiated output stream.
    * @throws NotAcceptable If unsupported Accept-Encoding value specified.
    * @throws IOException Thrown by underlying stream.
    */
   public FinishableServletOutputStream getNegotiatedOutputStream() throws NotAcceptable, IOException {
      if (os == null) {
         Encoder encoder = null;
         EncoderGroup encoders = restJavaMethod == null ? EncoderGroup.DEFAULT : restJavaMethod.encoders;

         String ae = request.getHeader("Accept-Encoding");
         if (! (ae == null || ae.isEmpty())) {
            EncoderMatch match = encoders.getEncoderMatch(ae);
            if (match == null) {
               // Identity should always match unless "identity;q=0" or "*;q=0" is specified.
               if (ae.matches(".*(identity|\\*)\\s*;\\s*q\\s*=\\s*(0(?!\\.)|0\\.0).*")) {
                  throw new NotAcceptable(
                     "Unsupported encoding in request header ''Accept-Encoding'': ''{0}''\n\tSupported codings: {1}",
                     ae, encoders.getSupportedEncodings()
                  );
               }
            } else {
               encoder = match.getEncoder();
               String encoding = match.getEncoding().toString();

               // Some clients don't recognize identity as an encoding, so don't set it.
               if (! encoding.equals("identity"))
                  setHeader("content-encoding", encoding);
            }
         }
         @SuppressWarnings("resource")
         ServletOutputStream sos = getOutputStream();
         os = new FinishableServletOutputStream(encoder == null ? sos : encoder.getOutputStream(sos));
      }
      return os;
   }

   @Override /* ServletResponse */
   public ServletOutputStream getOutputStream() throws IOException {
      if (sos == null)
         sos = inner.getOutputStream();
      return sos;
   }

   /**
    * Returns <jk>true</jk> if {@link #getOutputStream()} has been called.
    *
    * @return <jk>true</jk> if {@link #getOutputStream()} has been called.
    */
   public boolean getOutputStreamCalled() {
      return sos != null;
   }

   /**
    * Returns the writer to the response body.
    *
    * <p>
    * This methods bypasses any specified encoders and returns a regular unbuffered writer.
    * Use the {@link #getNegotiatedWriter()} method if you want to use the matched encoder (if any).
    */
   @Override /* ServletResponse */
   public PrintWriter getWriter() throws IOException {
      return getWriter(true, false);
   }

   /**
    * Convenience method meant to be used when rendering directly to a browser with no buffering.
    *
    * <p>
    * Sets the header <js>"x-content-type-options=nosniff"</js> so that output is rendered immediately on IE and Chrome
    * without any buffering for content-type sniffing.
    *
    * <p>
    * This can be useful if you want to render a streaming 'console' on a web page.
    *
    * @param contentType The value to set as the <c>Content-Type</c> on the response.
    * @return The raw writer.
    * @throws IOException Thrown by underlying stream.
    */
   public PrintWriter getDirectWriter(String contentType) throws IOException {
      setContentType(contentType);
      setHeader("X-Content-Type-Options", "nosniff");
      setHeader("Content-Encoding", "identity");
      return getWriter(true, true);
   }

   /**
    * Equivalent to {@link HttpServletResponse#getWriter()}, except wraps the output stream if an {@link Encoder} was
    * found that matched the <c>Accept-Encoding</c> header and sets the <c>Content-Encoding</c>
    * header to the appropriate value.
    *
    * @return The negotiated writer.
    * @throws NotAcceptable If unsupported charset in request header Accept-Charset.
    * @throws IOException Thrown by underlying stream.
    */
   public FinishablePrintWriter getNegotiatedWriter() throws NotAcceptable, IOException {
      return getWriter(false, false);
   }

   @SuppressWarnings("resource")
   private FinishablePrintWriter getWriter(boolean raw, boolean autoflush) throws NotAcceptable, IOException {
      if (w != null)
         return w;

      // If plain text requested, override it now.
      if (request.isPlainText())
         setHeader("Content-Type", "text/plain");

      try {
         OutputStream out = (raw ? getOutputStream() : getNegotiatedOutputStream());
         w = new FinishablePrintWriter(out, getCharacterEncoding(), autoflush);
         return w;
      } catch (UnsupportedEncodingException e) {
         String ce = getCharacterEncoding();
         setCharacterEncoding("UTF-8");
         throw new NotAcceptable("Unsupported charset in request header ''Accept-Charset'': ''{0}''", ce);
      }
   }

   /**
    * Returns the <c>Content-Type</c> header stripped of the charset attribute if present.
    *
    * @return The <c>media-type</c> portion of the <c>Content-Type</c> header.
    */
   public MediaType getMediaType() {
      return MediaType.of(getContentType());
   }

   /**
    * Wrapper around {@link #getCharacterEncoding()} that converts the value to a {@link Charset}.
    *
    * @return The request character encoding converted to a {@link Charset}.
    */
   public Charset getCharset() {
      String s = getCharacterEncoding();
      return s == null ? null : Charset.forName(s);
   }

   /**
    * Redirects to the specified URI.
    *
    * <p>
    * Relative URIs are always interpreted as relative to the context root.
    * This is similar to how WAS handles redirect requests, and is different from how Tomcat handles redirect requests.
    */
   @Override /* ServletResponse */
   public void sendRedirect(String uri) throws IOException {
      char c = (uri.length() > 0 ? uri.charAt(0) : 0);
      if (c != '/' && uri.indexOf("://") == -1)
         uri = request.getContextPath() + '/' + uri;
      super.sendRedirect(uri);
   }

   @Override /* ServletResponse */
   public void setHeader(String name, String value) {

      // Jetty doesn't set the content type correctly if set through this method.
      // Tomcat/WAS does.
      if (name.equalsIgnoreCase("Content-Type")) {
         super.setContentType(value);
         ContentType ct = ContentType.of(value);
         if (ct != null && ct.getParameter("charset") != null)
            super.setCharacterEncoding(ct.getParameter("charset"));
      } else {
         super.setHeader(name, value);
      }
   }

   /**
    * Same as {@link #setHeader(String, String)} but strips invalid characters from the value if present.
    *
    * These include CTRL characters, newlines, and non-ISO8859-1 characters.
    * Also limits the string length to 1024 characters.
    *
    * @param name Header name.
    * @param value Header value.
    */
   public void setHeaderSafe(String name, String value) {
      setHeaderSafe(name, value, 1024);
   }

   /**
    * Same as {@link #setHeader(String, String)} but strips invalid characters from the value if present.
    *
    * These include CTRL characters, newlines, and non-ISO8859-1 characters.
    *
    * @param name Header name.
    * @param value Header value.
    * @param maxLength
    *    The maximum length of the header value.
    *    Will be truncated with <js>"..."</js> added if the value exceeds the length.
    */
   public void setHeaderSafe(String name, String value, int maxLength) {

      // Jetty doesn't set the content type correctly if set through this method.
      // Tomcat/WAS does.
      if (name.equalsIgnoreCase("Content-Type"))
         super.setContentType(value);
      else
         super.setHeader(name, abbreviate(stripInvalidHttpHeaderChars(value), maxLength));
   }

   /**
    * Sets a header on the request.
    *
    * @param name The header name.
    * @param value The header value.
    *    <ul>
    *       <li>Can be any POJO.
    *       <li>Converted to a string using the specified part serializer.
    *    </ul>
    * @return This object (for method chaining).
    * @throws SchemaValidationException Header failed schema validation.
    * @throws SerializeException Header could not be serialized.
    */
   public RestResponse header(String name, Object value) throws SchemaValidationException, SerializeException {
      return header(null, null, name, value);
   }

   /**
    * Sets a header from a {@link NameValuePair}.
    *
    * <p>
    * Note that this bypasses the part serializer and set the header value directly.
    *
    * @param pair The header to set.  Nulls are ignored.
    * @return This object (for method chaining).
    */
   public RestResponse header(NameValuePair pair) {
      if (pair != null)
         setHeader(pair.getName(), pair.getValue());
      return this;
   }

   /**
    * Sets a header on the request.
    *
    * @param schema
    *    The schema to use to serialize the header, or <jk>null</jk> to use the default schema.
    * @param name The header name.
    * @param value The header value.
    *    <ul>
    *       <li>Can be any POJO.
    *       <li>Converted to a string using the specified part serializer.
    *    </ul>
    * @return This object (for method chaining).
    * @throws SchemaValidationException Header failed schema validation.
    * @throws SerializeException Header could not be serialized.
    */
   public RestResponse header(HttpPartSchema schema, String name, Object value) throws SchemaValidationException, SerializeException {
      return header(null, schema, name, value);
   }

   /**
    * Sets a header on the request.
    * @param serializer
    *    The serializer to use to serialize the header, or <jk>null</jk> to use the part serializer on the request.
    * @param schema
    *    The schema to use to serialize the header, or <jk>null</jk> to use the default schema.
    * @param name The header name.
    * @param value The header value.
    *    <ul>
    *       <li>Can be any POJO.
    *       <li>Converted to a string using the specified part serializer.
    *    </ul>
    * @return This object (for method chaining).
    * @throws SchemaValidationException Header failed schema validation.
    * @throws SerializeException Header could not be serialized.
    */
   public RestResponse header(HttpPartSerializerSession serializer, HttpPartSchema schema, String name, Object value) throws SchemaValidationException, SerializeException {
      if (serializer == null)
         serializer = request.getPartSerializer();
      setHeader(name, serializer.serialize(HEADER, schema, value));
      return this;
   }

   /**
    * Same as {@link #setHeader(String, String)} but header is defined as a response part
    *
    * @param h Header to set.
    * @throws SchemaValidationException Header part did not pass validation.
    * @throws SerializeException Header part could not be serialized.
    */
   public void setHeader(HttpPart h) throws SchemaValidationException, SerializeException {
      setHeaderSafe(h.getName(), h.getValue());
   }

   /**
    * Sets the <js>"Exception"</js> attribute to the specified throwable.
    *
    * <p>
    * This exception is used by {@link BasicRestCallLogger} for logging purposes.
    *
    * @param t The attribute value.
    * @return This object (for method chaining).
    */
   public RestResponse setException(Throwable t) {
      request.setException(t);
      return this;
   }

   /**
    * Sets the <js>"NoTrace"</js> attribute to the specified boolean.
    *
    * <p>
    * This flag is used by {@link BasicRestCallLogger} and tells it not to log the current request.
    *
    * @param b The attribute value.
    * @return This object (for method chaining).
    */
   public RestResponse setNoTrace(Boolean b) {
      request.setNoTrace(b);
      return this;
   }

   /**
    * Shortcut for calling <c>setNoTrace(<jk>true</jk>)</c>.
    *
    * @return This object (for method chaining).
    */
   public RestResponse setNoTrace() {
      return setNoTrace(true);
   }

   /**
    * Sets the <js>"Debug"</js> attribute to the specified boolean.
    *
    * <p>
    * This flag is used by {@link BasicRestCallLogger} to help determine how a request should be logged.
    *
    * @param b The attribute value.
    * @return This object (for method chaining).
    * @throws IOException If bodies could not be cached.
    */
   public RestResponse setDebug(Boolean b) throws IOException {
      request.setDebug(b);
      if (b)
         inner = CachingHttpServletResponse.wrap(inner);
      return this;
   }

   /**
    * Shortcut for calling <c>setDebug(<jk>true</jk>)</c>.
    *
    * @return This object (for method chaining).
    * @throws IOException If bodies could not be cached.
    */
   public RestResponse setDebug() throws IOException {
      return setDebug(true);
   }

   /**
    * Returns the metadata about this response.
    *
    * @return
    *    The metadata about this response.
    *    <jk>Never <jk>null</jk>.
    */
   public ResponseBeanMeta getResponseMeta() {
      return responseMeta;
   }

   /**
    * Sets metadata about this response.
    *
    * @param rbm The metadata about this response.
    * @return This object (for method chaining).
    */
   public RestResponse setResponseMeta(ResponseBeanMeta rbm) {
      this.responseMeta = rbm;
      return this;
   }

   /**
    * Returns <jk>true</jk> if this response object is of the specified type.
    *
    * @param c The type to check against.
    * @return <jk>true</jk> if this response object is of the specified type.
    */
   public boolean isOutputType(Class<?> c) {
      return c.isInstance(output);
   }

   /**
    * Returns this value cast to the specified class.
    *
    * @param c The class to cast to.
    * @return This value cast to the specified class.
    */
   @SuppressWarnings("unchecked")
   public <T> T getOutput(Class<T> c) {
      return (T)output;
   }

   /**
    * Returns the wrapped servlet request.
    *
    * @return The wrapped servlet request.
    */
   protected HttpServletResponse getInner() {
      return inner;
   }

   @Override /* ServletResponse */
   public void flushBuffer() throws IOException {
      if (w != null)
         w.flush();
      if (os != null)
         os.flush();
      super.flushBuffer();
   }
}