[ Servlet&JSP ] HttpServletResponse 기능

 

HTTP Response Header

 

1. Response Status

response.setStatus(번호);

response.setStatus(HttpServletResponse.SC_OK); 

response.setStatus(200); //성공
response.setStatus(HttpServletResponse.SC_OK); //200 성공
response.setStatus(HttpServletResponse.SC_BAD_REQUEST); //실패 400

 

 

HttpServletResponse 클래스에서 응답상태 코드를 볼 수 있다. 

 

📑 HttpServletResponse

/*
 * 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 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).
 *
 * @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 in it, 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.
     *
     * @param url
     *            the url to be encoded.
     * @return the encoded URL if encoding is needed; the unchanged URL
     *         otherwise.
     */
    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. 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.
     *
     * @param url
     *            the url to be encoded.
     * @return the encoded URL if encoding is needed; the unchanged URL
     *         otherwise.
     * @see #sendRedirect
     * @see #encodeUrl
     */
    public String encodeRedirectURL(String url);

    /**
     * @param url
     *            the url to be encoded.
     * @return the encoded URL if encoding is needed; the unchanged URL
     *         otherwise.
     * @deprecated As of version 2.1, use encodeURL(String url) instead
     */
    @Deprecated
    public String encodeUrl(String url);

    /**
     * @param url
     *            the url to be encoded.
     * @return the encoded URL if encoding is needed; the unchanged URL
     *         otherwise.
     * @deprecated As of version 2.1, use encodeRedirectURL(String url) instead
     */
    @Deprecated
    public String encodeRedirectUrl(String url);

    /**
     * Sends an error response to the client using the specified status code and
     * clears the output 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", leaving cookies and
     * other headers unmodified. 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.
     * <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. This is equivalent to calling {@link #sendError(int,
     * String)} with the same status code and <code>null</code> for the message.
     *
     * @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. 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.
     * <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. This method is used to set the
     * return status code when there is no error (for example, for the status
     * codes SC_OK or SC_MOVED_TEMPORARILY). If there is an error, and the
     * caller wishes to invoke an error-page defined in the web application, the
     * <code>sendError</code> method should be used instead.
     * <p>
     * The container clears the buffer and sets the Location header, preserving
     * cookies and other headers.
     *
     * @param sc
     *            the status code
     * @see #sendError
     */
    public void setStatus(int sc);

    /**
     * Sets the status code and message for this response.
     *
     * @param sc
     *            the status code
     * @param sm
     *            the status message
     * @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>.
     */
    @Deprecated
    public void setStatus(int sc, String sm);

    /**
     * Get the HTTP status code for this Response.
     *
     * @return The HTTP status code for this Response
     *
     * @since Servlet 3.0
     */
    public int getStatus();

    /**
     * Return the value for the specified header, or <code>null</code> if this
     * header has not been set.  If more than one value was added for this
     * name, only the first is returned; use {@link #getHeaders(String)} to
     * retrieve all of them.
     *
     * @param name Header name to look up
     *
     * @return The first value for the specified header. This is the raw value
     *         so if multiple values are specified in the first header then they
     *         will be returned as a single header value .
     *
     * @since Servlet 3.0
     */
    public String getHeader(String name);

    /**
     * Return a Collection of all the header values associated with the
     * specified header name.
     *
     * @param name Header name to look up
     *
     * @return The values for the specified header. These are the raw values so
     *         if multiple values are specified in a single header that will be
     *         returned as a single header value.
     *
     * @since Servlet 3.0
     */
    public Collection<String> getHeaders(String name);

    /**
     * Get the header names set for this HTTP response.
     *
     * @return The header names set for this HTTP response.
     *
     * @since Servlet 3.0
     */
    public Collection<String> getHeaderNames();

    /**
     * Configure the supplier of the trailer headers. The supplier will be
     * called in the scope of the thread that completes the response.
     * <br>
     * Trailers that don't meet the requirements of RFC 7230, section 4.1.2 will
     * be ignored.
     * <br>
     * The default implementation is a NO-OP.
     *
     * @param supplier The supplier for the trailer headers
     *
     * @throws IllegalStateException if this method is called when the
     *         underlying protocol does not support trailer headers or if using
     *         HTTP/1.1 and the response has already been committed
     *
     * @since Servlet 4.0
     */
    public default void setTrailerFields(Supplier<Map<String, String>> supplier) {
        // NO-OP
    }

    /**
     * Obtain the supplier of the trailer headers.
     * <br>
     * The default implementation returns null.
     *
     * @return The supplier for the trailer headers
     *
     * @since Servlet 4.0
     */
    public default Supplier<Map<String, String>> getTrailerFields() {
        return null;
    }

    /*
     * Server status codes; see RFC 7231.
     */

    /**
     * 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;
}

 

 

 

2. Response header

1) response.setHeader("이름","값");

response.setHeader("content-Type","text/plan;charset=utf-8"); //컨텐츠 타입
response.setHeader("Cache-Control","no-cache, no-store, must-revalidate"); //캐쉬 무효화
response.setHeader("Pragma","no-cache"); //과거 캐쉬 무효화
response.setHeader("my-header","hello"); //원하는 임의의 값을 넣을 수 있음.

2) 편의 메서드

response.setContentType("text/plain");
response.setCharacterEncoding("utf-8");
response.setContentLength(2); //(생략시 자동 생성)

 

 

3. Cookie ( Response header )

Set-Cookie: myCookie=good; Max-Age=600;  쿠키 유효 시간 600

 

1) response.setHeader("이름","값");

response.setHeader("Set-Cookie", "myCookie=good; Max-Age=600");

 

2) Cookie 클래스

Cookie cookie = new Cookie("myCookie", "good");
cookie.setMaxAge(600); //600초
response.addCookie(cookie);

 

 

 

4. Redirect ( Response  header )

Status Code 302
Location: /basic/hello-form.html

 

1) response.setHeader("이름","값");

response.setStatus(HttpServletResponse.SC_FOUND); //302
response.setHeader("Location", "/basic/hello-form.html");

 

2) 편의 메서드

response.sendRedirect("이동 경로");

response.sendRedirect("/basic/hello-form.html");

 

 

 

 

4. 응답 데이터

1) 단순 텍스트 응답

PrintWriter writer = response.getWriter();
writer.println("ok");

 

2) HTML 응답

//1. 컨텐츠 타입
response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
//2. html 출력 
PrintWriter writer = response.getWriter();
writer.println("<html>");
writer.println("<body>");
writer.println("<div>html 전달합니다.</div>");
writer.println("</body>");
writer.println("</html>");

 

 

3) HTTP API - JSON 응답

//1. 컨텐츠 타입
response.setContentType("application/json");
response.setCharacterEncoding("utf-8");

//2. 전달할 객체 생성
HelloData helloData = new HelloData();
helloData.setUsername("lee");
helloData.setAge(10);

//3-1. json 형태로 변환하려면 ObjectMapper가  필요하다.
//3-2. json 형태로 변환 {"username":"lee","age":10}
String result = objectMapper.writeValueAsString(helloData);

//4. 클라이언트 전달
response.getWriter().write(result);

//3-1. json 형태로 변환하려면 ObjectMapper가  필요하다.
private ObjectMapper objectMapper = new ObjectMapper();