Java tutorial
/* * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved. * Copyright 2004 The Apache Software Foundation * * 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 javax.servlet.http; import java.io.IOException; import java.util.Collection; import java.util.Map; import java.util.function.Supplier; import javax.servlet.ServletResponse; /** * * Extends the {@link ServletResponse} interface to provide HTTP-specific * functionality in sending a response. For example, it has methods * to access HTTP headers and cookies. * * <p>The servlet container creates an <code>HttpServletResponse</code> object * and passes it as an argument to the servlet's service methods * (<code>doGet</code>, <code>doPost</code>, etc). * * * @author Various * * @see javax.servlet.ServletResponse * */ public interface HttpServletResponse extends ServletResponse { /** * Adds the specified cookie to the response. This method can be called * multiple times to set more than one cookie. * * @param cookie the Cookie to return to the client * */ public void addCookie(Cookie cookie); /** * Returns a boolean indicating whether the named response header * has already been set. * * @param name the header name * @return <code>true</code> if the named response header * has already been set; * <code>false</code> otherwise */ public boolean containsHeader(String name); /** * Encodes the specified URL by including the session ID, * or, if encoding is not needed, returns the URL unchanged. * The implementation of this method includes the logic to * determine whether the session ID needs to be encoded in the URL. * For example, if the browser supports cookies, or session * tracking is turned off, URL encoding is unnecessary. * * <p>For robust session tracking, all URLs emitted by a servlet * should be run through this * method. Otherwise, URL rewriting cannot be used with browsers * which do not support cookies. * * <p>If the URL is relative, it is always relative to the current * HttpServletRequest. * * @param url the url to be encoded. * @return the encoded URL if encoding is needed; * the unchanged URL otherwise. * @exception IllegalArgumentException if the url is not valid */ public String encodeURL(String url); /** * Encodes the specified URL for use in the * <code>sendRedirect</code> method or, if encoding is not needed, * returns the URL unchanged. The implementation of this method * includes the logic to determine whether the session ID * needs to be encoded in the URL. For example, if the browser supports * cookies, or session tracking is turned off, URL encoding is * unnecessary. Because the rules for making this determination can * differ from those used to decide whether to * encode a normal link, this method is separated from the * <code>encodeURL</code> method. * * <p>All URLs sent to the <code>HttpServletResponse.sendRedirect</code> * method should be run through this method. Otherwise, URL * rewriting cannot be used with browsers which do not support * cookies. * * <p>If the URL is relative, it is always relative to the current * HttpServletRequest. * * @param url the url to be encoded. * @return the encoded URL if encoding is needed; * the unchanged URL otherwise. * @exception IllegalArgumentException if the url is not valid * * @see #sendRedirect * @see #encodeUrl */ public String encodeRedirectURL(String url); /** * @deprecated As of version 2.1, use encodeURL(String url) instead * * @param url the url to be encoded. * @return the encoded URL if encoding is needed; * the unchanged URL otherwise. * @exception IllegalArgumentException if the url is not valid */ @Deprecated public String encodeUrl(String url); /** * @deprecated As of version 2.1, use * encodeRedirectURL(String url) instead * * @param url the url to be encoded. * @return the encoded URL if encoding is needed; * the unchanged URL otherwise. * @exception IllegalArgumentException if the url is not valid */ @Deprecated public String encodeRedirectUrl(String url); /** * <p>Sends an error response to the client using the specified * status and clears the buffer. The server defaults to creating * the response to look like an HTML-formatted server error page * containing the specified message, setting the content type to * "text/html". The caller is <strong>not</strong> responsible for * escaping or re-encoding the message to ensure it is safe with * respect to the current response encoding and content type. This * aspect of safety is the responsibility of the container, as it is * generating the error page containing the message. The server * will preserve cookies and may clear or update any headers needed * to serve the error page as a valid response.</p> * * <p>If an error-page declaration has been made for the web * application corresponding to the status code passed in, it will * be served back in preference to the suggested msg parameter and * the msg parameter will be ignored.</p> * * <p>If the response has already been committed, this method throws * an IllegalStateException. * After using this method, the response should be considered * to be committed and should not be written to. * * @param sc the error status code * @param msg the descriptive message * @exception IOException If an input or output exception occurs * @exception IllegalStateException If the response was committed */ public void sendError(int sc, String msg) throws IOException; /** * Sends an error response to the client using the specified status * code and clears the buffer. * * The server will preserve cookies and may clear or * update any headers needed to serve the error page as a valid response. * * If an error-page declaration has been made for the web application * corresponding to the status code passed in, it will be served back * the error page * * <p>If the response has already been committed, this method throws * an IllegalStateException. * After using this method, the response should be considered * to be committed and should not be written to. * * @param sc the error status code * @exception IOException If an input or output exception occurs * @exception IllegalStateException If the response was committed * before this method call */ public void sendError(int sc) throws IOException; /** * Sends a temporary redirect response to the client using the * specified redirect location URL and clears the buffer. The buffer will * be replaced with the data set by this method. Calling this method sets the * status code to {@link #SC_FOUND} 302 (Found). * This method can accept relative URLs;the servlet container must convert * the relative URL to an absolute URL * before sending the response to the client. If the location is relative * without a leading '/' the container interprets it as relative to * the current request URI. If the location is relative with a leading * '/' the container interprets it as relative to the servlet container root. * If the location is relative with two leading '/' the container interprets * it as a network-path reference (see * <a href="http://www.ietf.org/rfc/rfc3986.txt"> * RFC 3986: Uniform Resource Identifier (URI): Generic Syntax</a>, section 4.2 * "Relative Reference"). * * <p>If the response has already been committed, this method throws * an IllegalStateException. * After using this method, the response should be considered * to be committed and should not be written to. * * @param location the redirect location URL * @exception IOException If an input or output exception occurs * @exception IllegalStateException If the response was committed or * if a partial URL is given and cannot be converted into a valid URL */ public void sendRedirect(String location) throws IOException; /** * * Sets a response header with the given name and * date-value. The date is specified in terms of * milliseconds since the epoch. If the header had already * been set, the new value overwrites the previous one. The * <code>containsHeader</code> method can be used to test for the * presence of a header before setting its value. * * @param name the name of the header to set * @param date the assigned date value * * @see #containsHeader * @see #addDateHeader */ public void setDateHeader(String name, long date); /** * * Adds a response header with the given name and * date-value. The date is specified in terms of * milliseconds since the epoch. This method allows response headers * to have multiple values. * * @param name the name of the header to set * @param date the additional date value * * @see #setDateHeader */ public void addDateHeader(String name, long date); /** * * Sets a response header with the given name and value. * If the header had already been set, the new value overwrites the * previous one. The <code>containsHeader</code> method can be * used to test for the presence of a header before setting its * value. * * @param name the name of the header * @param value the header value If it contains octet string, * it should be encoded according to RFC 2047 * (http://www.ietf.org/rfc/rfc2047.txt) * * @see #containsHeader * @see #addHeader */ public void setHeader(String name, String value); /** * Adds a response header with the given name and value. * This method allows response headers to have multiple values. * * @param name the name of the header * @param value the additional header value If it contains * octet string, it should be encoded * according to RFC 2047 * (http://www.ietf.org/rfc/rfc2047.txt) * * @see #setHeader */ public void addHeader(String name, String value); /** * Sets a response header with the given name and * integer value. If the header had already been set, the new value * overwrites the previous one. The <code>containsHeader</code> * method can be used to test for the presence of a header before * setting its value. * * @param name the name of the header * @param value the assigned integer value * * @see #containsHeader * @see #addIntHeader */ public void setIntHeader(String name, int value); /** * Adds a response header with the given name and * integer value. This method allows response headers to have multiple * values. * * @param name the name of the header * @param value the assigned integer value * * @see #setIntHeader */ public void addIntHeader(String name, int value); /** * Sets the status code for this response. * * <p>This method is used to set the return status code when there is * no error (for example, for the SC_OK or SC_MOVED_TEMPORARILY status * codes). * * <p>If this method is used to set an error code, then the container's * error page mechanism will not be triggered. If there is an error and * the caller wishes to invoke an error page defined in the web * application, then {@link #sendError} must be used instead. * * <p>This method preserves any cookies and other response headers. * * <p>Valid status codes are those in the 2XX, 3XX, 4XX, and 5XX ranges. * Other status codes are treated as container specific. * * @param sc the status code * * @see #sendError */ public void setStatus(int sc); /** * @deprecated As of version 2.1, due to ambiguous meaning of the * message parameter. To set a status code * use <code>setStatus(int)</code>, to send an error with a description * use <code>sendError(int, String)</code>. * * Sets the status code and message for this response. * * @param sc the status code * @param sm the status message */ @Deprecated public void setStatus(int sc, String sm); /** * Gets the current status code of this response. * * @return the current status code of this response * * @since Servlet 3.0 */ public int getStatus(); /** * Gets the value of the response header with the given name. * * <p>If a response header with the given name exists and contains * multiple values, the value that was added first will be returned. * * <p>This method considers only response headers set or added via * {@link #setHeader}, {@link #addHeader}, {@link #setDateHeader}, * {@link #addDateHeader}, {@link #setIntHeader}, or * {@link #addIntHeader}, respectively. * * @param name the name of the response header whose value to return * * @return the value of the response header with the given name, * or <tt>null</tt> if no header with the given name has been set * on this response * * @since Servlet 3.0 */ public String getHeader(String name); /** * Gets the values of the response header with the given name. * * <p>This method considers only response headers set or added via * {@link #setHeader}, {@link #addHeader}, {@link #setDateHeader}, * {@link #addDateHeader}, {@link #setIntHeader}, or * {@link #addIntHeader}, respectively. * * <p>Any changes to the returned <code>Collection</code> must not * affect this <code>HttpServletResponse</code>. * * @param name the name of the response header whose values to return * * @return a (possibly empty) <code>Collection</code> of the values * of the response header with the given name * * @since Servlet 3.0 */ public Collection<String> getHeaders(String name); /** * Gets the names of the headers of this response. * * <p>This method considers only response headers set or added via * {@link #setHeader}, {@link #addHeader}, {@link #setDateHeader}, * {@link #addDateHeader}, {@link #setIntHeader}, or * {@link #addIntHeader}, respectively. * * <p>Any changes to the returned <code>Collection</code> must not * affect this <code>HttpServletResponse</code>. * * @return a (possibly empty) <code>Collection</code> of the names * of the headers of this response * * @since Servlet 3.0 */ public Collection<String> getHeaderNames(); /** * Sets the supplier of trailer headers. * * <p>The trailer header field value is defined as a comma-separated list * (see Section 3.2.2 and Section 4.1.2 of RFC 7230).</p> * * <p>The supplier will be called within the scope of whatever thread/call * causes the response content to be completed. Typically this will * be any thread calling close() on the output stream or writer.</p> * * <p>The trailers that run afoul of the provisions of section 4.1.2 of * RFC 7230 are ignored.</p> * * <p>The RFC requires the name of every key that is to be in the * supplied Map is included in the comma separated list that is the value * of the "Trailer" response header. The application is responsible for * ensuring this requirement is met. Failure to do so may lead to * interoperability failures.</p> * * @implSpec * The default implementation is a no-op. * * @param supplier the supplier of trailer headers * * @exception IllegalStateException if it is invoked after the response has * has been committed, * or the trailer is not supported in the request, for instance, * the underlying protocol is HTTP 1.0, or the response is not * in chunked encoding in HTTP 1.1. * * @since Servlet 4.0 */ default public void setTrailerFields(Supplier<Map<String, String>> supplier) { } /** * Gets the supplier of trailer headers. * * @implSpec * The default implememtation return null. * * @return <code>Supplier</code> of trailer headers * * @since Servlet 4.0 */ default public Supplier<Map<String, String>> getTrailerFields() { return null; } /* * Server status codes; see RFC 2068. */ /** * Status code (100) indicating the client can continue. */ public static final int SC_CONTINUE = 100; /** * Status code (101) indicating the server is switching protocols * according to Upgrade header. */ public static final int SC_SWITCHING_PROTOCOLS = 101; /** * Status code (200) indicating the request succeeded normally. */ public static final int SC_OK = 200; /** * Status code (201) indicating the request succeeded and created * a new resource on the server. */ public static final int SC_CREATED = 201; /** * Status code (202) indicating that a request was accepted for * processing, but was not completed. */ public static final int SC_ACCEPTED = 202; /** * Status code (203) indicating that the meta information presented * by the client did not originate from the server. */ public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203; /** * Status code (204) indicating that the request succeeded but that * there was no new information to return. */ public static final int SC_NO_CONTENT = 204; /** * Status code (205) indicating that the agent <em>SHOULD</em> reset * the document view which caused the request to be sent. */ public static final int SC_RESET_CONTENT = 205; /** * Status code (206) indicating that the server has fulfilled * the partial GET request for the resource. */ public static final int SC_PARTIAL_CONTENT = 206; /** * Status code (300) indicating that the requested resource * corresponds to any one of a set of representations, each with * its own specific location. */ public static final int SC_MULTIPLE_CHOICES = 300; /** * Status code (301) indicating that the resource has permanently * moved to a new location, and that future references should use a * new URI with their requests. */ public static final int SC_MOVED_PERMANENTLY = 301; /** * Status code (302) indicating that the resource has temporarily * moved to another location, but that future references should * still use the original URI to access the resource. * * This definition is being retained for backwards compatibility. * SC_FOUND is now the preferred definition. */ public static final int SC_MOVED_TEMPORARILY = 302; /** * Status code (302) indicating that the resource reside * temporarily under a different URI. Since the redirection might * be altered on occasion, the client should continue to use the * Request-URI for future requests.(HTTP/1.1) To represent the * status code (302), it is recommended to use this variable. */ public static final int SC_FOUND = 302; /** * Status code (303) indicating that the response to the request * can be found under a different URI. */ public static final int SC_SEE_OTHER = 303; /** * Status code (304) indicating that a conditional GET operation * found that the resource was available and not modified. */ public static final int SC_NOT_MODIFIED = 304; /** * Status code (305) indicating that the requested resource * <em>MUST</em> be accessed through the proxy given by the * <code><em>Location</em></code> field. */ public static final int SC_USE_PROXY = 305; /** * Status code (307) indicating that the requested resource * resides temporarily under a different URI. The temporary URI * <em>SHOULD</em> be given by the <code><em>Location</em></code> * field in the response. */ public static final int SC_TEMPORARY_REDIRECT = 307; /** * Status code (400) indicating the request sent by the client was * syntactically incorrect. */ public static final int SC_BAD_REQUEST = 400; /** * Status code (401) indicating that the request requires HTTP * authentication. */ public static final int SC_UNAUTHORIZED = 401; /** * Status code (402) reserved for future use. */ public static final int SC_PAYMENT_REQUIRED = 402; /** * Status code (403) indicating the server understood the request * but refused to fulfill it. */ public static final int SC_FORBIDDEN = 403; /** * Status code (404) indicating that the requested resource is not * available. */ public static final int SC_NOT_FOUND = 404; /** * Status code (405) indicating that the method specified in the * <code><em>Request-Line</em></code> is not allowed for the resource * identified by the <code><em>Request-URI</em></code>. */ public static final int SC_METHOD_NOT_ALLOWED = 405; /** * Status code (406) indicating that the resource identified by the * request is only capable of generating response entities which have * content characteristics not acceptable according to the accept * headers sent in the request. */ public static final int SC_NOT_ACCEPTABLE = 406; /** * Status code (407) indicating that the client <em>MUST</em> first * authenticate itself with the proxy. */ public static final int SC_PROXY_AUTHENTICATION_REQUIRED = 407; /** * Status code (408) indicating that the client did not produce a * request within the time that the server was prepared to wait. */ public static final int SC_REQUEST_TIMEOUT = 408; /** * Status code (409) indicating that the request could not be * completed due to a conflict with the current state of the * resource. */ public static final int SC_CONFLICT = 409; /** * Status code (410) indicating that the resource is no longer * available at the server and no forwarding address is known. * This condition <em>SHOULD</em> be considered permanent. */ public static final int SC_GONE = 410; /** * Status code (411) indicating that the request cannot be handled * without a defined <code><em>Content-Length</em></code>. */ public static final int SC_LENGTH_REQUIRED = 411; /** * Status code (412) indicating that the precondition given in one * or more of the request-header fields evaluated to false when it * was tested on the server. */ public static final int SC_PRECONDITION_FAILED = 412; /** * Status code (413) indicating that the server is refusing to process * the request because the request entity is larger than the server is * willing or able to process. */ public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413; /** * Status code (414) indicating that the server is refusing to service * the request because the <code><em>Request-URI</em></code> is longer * than the server is willing to interpret. */ public static final int SC_REQUEST_URI_TOO_LONG = 414; /** * Status code (415) indicating that the server is refusing to service * the request because the entity of the request is in a format not * supported by the requested resource for the requested method. */ public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415; /** * Status code (416) indicating that the server cannot serve the * requested byte range. */ public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416; /** * Status code (417) indicating that the server could not meet the * expectation given in the Expect request header. */ public static final int SC_EXPECTATION_FAILED = 417; /** * Status code (500) indicating an error inside the HTTP server * which prevented it from fulfilling the request. */ public static final int SC_INTERNAL_SERVER_ERROR = 500; /** * Status code (501) indicating the HTTP server does not support * the functionality needed to fulfill the request. */ public static final int SC_NOT_IMPLEMENTED = 501; /** * Status code (502) indicating that the HTTP server received an * invalid response from a server it consulted when acting as a * proxy or gateway. */ public static final int SC_BAD_GATEWAY = 502; /** * Status code (503) indicating that the HTTP server is * temporarily overloaded, and unable to handle the request. */ public static final int SC_SERVICE_UNAVAILABLE = 503; /** * Status code (504) indicating that the server did not receive * a timely response from the upstream server while acting as * a gateway or proxy. */ public static final int SC_GATEWAY_TIMEOUT = 504; /** * Status code (505) indicating that the server does not support * or refuses to support the HTTP protocol version that was used * in the request message. */ public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505; }