From 3324545626f8f93c43e3b54cf56004d19af17da2 Mon Sep 17 00:00:00 2001 From: Kai Moritz Date: Sun, 27 Nov 2011 00:03:33 +0100 Subject: [PATCH] AcceleratorFilter implementiert MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Der Filter belauscht das Setzen der Header und konfiguriert CacheControl entsprechend. Auf diesem Weg lassen sich Java-Webanwendungen mit verbessertem Caching-Verhalten ausstatten, ohne dass dafür an der Anwendung selbst etwas geändert werden müsste. --- .../juplo/cachecontrol/AcceleratorFilter.java | 267 ++++++++++++++++++ .../juplo/cachecontrol/CacheControl.java | 165 +++++------ .../cachecontrol/CacheControlFilter.java | 209 -------------- .../juplo/cachecontrol/HeaderNames.java | 21 ++ 4 files changed, 372 insertions(+), 290 deletions(-) create mode 100644 cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/AcceleratorFilter.java delete mode 100644 cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControlFilter.java create mode 100644 cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/HeaderNames.java diff --git a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/AcceleratorFilter.java b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/AcceleratorFilter.java new file mode 100644 index 00000000..82c40822 --- /dev/null +++ b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/AcceleratorFilter.java @@ -0,0 +1,267 @@ +package de.halbekunst.juplo.cachecontrol; + +import de.halbekunst.juplo.cachecontrol.CacheControl.CacheMethodHandle; +import java.io.IOException; +import java.io.OutputStream; +import java.io.PrintWriter; +import java.util.Enumeration; +import java.util.Map; +import java.util.zip.GZIPOutputStream; +import javax.servlet.Filter; +import javax.servlet.FilterChain; +import javax.servlet.FilterConfig; +import javax.servlet.ServletException; +import javax.servlet.ServletOutputStream; +import javax.servlet.ServletRequest; +import javax.servlet.ServletResponse; +import javax.servlet.http.HttpServletRequest; +import javax.servlet.http.HttpServletResponse; +import javax.servlet.http.HttpServletResponseWrapper; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import org.springframework.beans.factory.annotation.Autowired; +import org.springframework.beans.factory.annotation.Configurable; + + + +/** + * + * @author kai + */ +@Configurable +public class AcceleratorFilter implements Filter { + private final static Logger log = LoggerFactory.getLogger(AcceleratorFilter.class); + + public final static String REQUEST_URI_ATTRIBUTE = "javax.servlet.include.request_uri"; + + + @Autowired CacheControl cacheControl; + @Autowired(required=true) Integer buffer; + @Autowired(required=true) String eTag; + @Autowired(required=true) Boolean weak; + @Autowired(required=true) Long lastModified; + @Autowired(required=true) Integer cacheSeconds; + + + @Override + public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { + if (!(request instanceof HttpServletRequest)) { + log.error("AcceleratorFilter can only handle HTTP-requests"); + chain.doFilter(request, response); + return; + } + + /** Prüfen, ob es sich um eine Anfrage für einen JSP-Include handelt */ + if (request.getAttribute(REQUEST_URI_ATTRIBUTE) != null) { + log.debug("Includes cannot be accelerated"); + chain.doFilter(request, response); + return; + } + + AccelerationWrapper wrapper = new AccelerationWrapper((HttpServletRequest)request, (HttpServletResponse)response); + cacheControl.init(wrapper); + chain.doFilter(request, wrapper); + wrapper.finish(); + } + + @Override + public void init(FilterConfig filterConfig) throws ServletException { + } + + @Override + public void destroy() { + } + + + class AccelerationWrapper extends HttpServletResponseWrapper implements CacheMethodHandle { + + private final HttpServletRequest request; + private final HttpServletResponse response; + + private boolean zipped; + private GZIPServletOutputStream out; + + private long now; + private int buffer; + private int status; + private String type; + + + AccelerationWrapper(HttpServletRequest request, HttpServletResponse response) throws IOException { + super(response); + + this.request = request; + this.response = response; + + now = System.currentTimeMillis(); + buffer = AcceleratorFilter.this.buffer; + status = HttpServletResponse.SC_OK; + + zipped = false; + Enumeration values = request.getHeaders(HeaderNames.HEADER_ACCEPT_ENCODING); + while (values.hasMoreElements()) { + String value = (String) values.nextElement(); + if (value.indexOf("gzip") != -1) { + zipped = true; + response.addHeader(HeaderNames.HEADER_CONTENT_ENCODING, "gzip"); + break; + } + } + } + + + public void finish() throws IOException { + if (zipped && out != null) + out.zout.finish(); + } + + + @Override + public void setStatus(int sc) { + response.setStatus(sc); + status = sc; + try { + cacheControl.decorate(request, response, this); + } + catch (Exception e) { + log.error("Error while decorating response", e); + } + } + + @Override + public void setStatus(int sc, String sm) { + response.setStatus(sc,sm); + status = sc; + try { + cacheControl.decorate(request, response, this); + } + catch (Exception e) { + log.error("Error while decorating response", e); + } + } + + @Override + public ServletOutputStream getOutputStream() throws IOException { + if (out == null) + out = new GZIPServletOutputStream(response.getOutputStream(), zipped); + return out; + } + + @Override + public PrintWriter getWriter() throws IOException { + return new PrintWriter(getOutputStream()); + } + + @Override + public void setContentType(String type) { + this.type = type; + response.setContentType(type); + } + + @Override + public void setBufferSize(int size) { + this.buffer = size; + response.setBufferSize(size); + } + + @Override + public int getBufferSize() { + return buffer; + } + + @Override + public void flushBuffer() throws IOException { + cacheControl.decorate(request, response, this); + if (zipped && out != null) { + out.zout.finish(); + } + response.flushBuffer(); + } + + @Override + public void resetBuffer() { + response.resetBuffer(); + } + + @Override + public boolean isCommitted() { + return response.isCommitted(); + } + + @Override + public void reset() { + response.reset(); + } + + + + @Override + public long getTimestamp() { + return now; + } + + @Override + public int accepts(HttpServletRequest request) { + return status; + } + + @Override + public int getCacheSeconds(HttpServletRequest request) { + return cacheSeconds; + } + + @Override + public long getLastModified(HttpServletRequest request) { + return lastModified; + } + + @Override + public String getETag(HttpServletRequest request) { + return eTag; + } + + @Override + public boolean isETagWeak() { + return weak; + } + + @Override + public void cacheControl(HttpServletRequest request, Map cacheControlMap) { + } + + + class GZIPServletOutputStream extends ServletOutputStream { + + private final OutputStream out; + private final GZIPOutputStream zout; + private boolean untouched = true; + + public GZIPServletOutputStream(ServletOutputStream out, boolean zipped) throws IOException { + if (zipped) { + this.zout = new GZIPOutputStream(out, buffer); + this.out = this.zout; + } + else { + this.out = out; + this.zout = null; + } + } + + + @Override + public void write(int i) throws IOException { + if (untouched) { + untouched = false; + try { + AcceleratorFilter.this.cacheControl.decorate(AccelerationWrapper.this.request, response, buffer); + } + catch (Exception e) { + log.error("Error while guessing Cache-Header's", e); + response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR); + } + } + out.write(i); + } + } + } +} diff --git a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControl.java b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControl.java index 77e2004c..19a60b51 100644 --- a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControl.java +++ b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControl.java @@ -5,7 +5,6 @@ import de.halbekunst.juplo.cachecontrol.annotations.Accepts; import de.halbekunst.juplo.cachecontrol.annotations.LastModified; import de.halbekunst.juplo.cachecontrol.annotations.ETag; import java.lang.annotation.Annotation; -import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.Date; import java.util.Map; @@ -23,32 +22,25 @@ import org.slf4j.LoggerFactory; public class CacheControl { private final static Logger log = LoggerFactory.getLogger(CacheControl.class); - public static final String HEADER_DATE = "Date"; - public static final String HEADER_CACHE_CONTROL = "Cache-Control"; - public static final String HEADER_LAST_MODIFIED = "Last-Modified"; - public static final String HEADER_ETAG = "ETag"; - public static final String HEADER_EXPIRES = "Expires"; - public static final String HEADER_PRAGMA = "Pragma"; - public static final String HEADER_IF_MODIFIED_SINCE = "If-Modified-Since"; - public static final String HEADER_IF_NONE_MATCH = "If-None-Match"; - public static final String HEADER_RANGE = "Range"; - private static final ThreadLocal tl = new ThreadLocal(); private Integer defaultCacheSeconds; private Long defaultLastModified; - public void init(Object handler) throws Exception { - if (CacheControl.tl.get() == null) - CacheControl.tl.set(new ReflectionCacheMethodHandle(handler)); + public void init(CacheMethodHandle handle) { + CacheControl.tl.set(handle); + } + + public void init(Object handler) throws NoSuchMethodException { + CacheControl.tl.set(new ReflectionCacheMethodHandle(handler)); } public boolean decorate( HttpServletRequest request, HttpServletResponse response, Object handler - ) throws Exception + ) { try { CacheMethodHandle controller = CacheControl.tl.get(); @@ -64,7 +56,7 @@ public class CacheControl { * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.18 RFC 2616, * Abschnitt 14.18} einen Date-Header enthalten */ - response.setDateHeader(HEADER_DATE, controller.getTimestamp()); + response.setDateHeader(HeaderNames.HEADER_DATE, controller.getTimestamp()); /** Besondere Maßnahmen für besondere HTTP-Status-Codes ?!? */ int status = controller.accepts(request); @@ -95,11 +87,6 @@ public class CacheControl { case HttpServletResponse.SC_NOT_IMPLEMENTED: // 501 case HttpServletResponse.SC_SERVICE_UNAVAILABLE: // 503 case HttpServletResponse.SC_HTTP_VERSION_NOT_SUPPORTED: // 505 - /** - * Ein Fehlercode kann stellvertretend für den Handler gesendet werden, - * da im Fehlerfall eh keine weiteren Daten ausgegeben werden! - */ - response.sendError(status); return true; default: /** @@ -126,20 +113,20 @@ public class CacheControl { int cacheSeconds = controller.getCacheSeconds(request); if (cacheSeconds < 1) { log.debug("{}: caching disabled!", url); - response.setDateHeader(HEADER_DATE, controller.getTimestamp()); - response.setDateHeader(HEADER_EXPIRES, 0); - response.addHeader(HEADER_PRAGMA, "no-cache"); - response.addHeader(HEADER_CACHE_CONTROL, "private"); - response.addHeader(HEADER_CACHE_CONTROL, "no-cache"); - response.addHeader(HEADER_CACHE_CONTROL, "no-store"); - response.addHeader(HEADER_CACHE_CONTROL, "max-age=0"); - response.addHeader(HEADER_CACHE_CONTROL, "s-max-age=0"); + response.setDateHeader(HeaderNames.HEADER_DATE, controller.getTimestamp()); + response.setDateHeader(HeaderNames.HEADER_EXPIRES, 0); + response.addHeader(HeaderNames.HEADER_PRAGMA, "no-cache"); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, "private"); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, "no-cache"); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, "no-store"); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, "max-age=0"); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, "s-max-age=0"); return true; } long ifModifiedSince = -1; try { - ifModifiedSince = request.getDateHeader(HEADER_IF_MODIFIED_SINCE); + ifModifiedSince = request.getDateHeader(HeaderNames.HEADER_IF_MODIFIED_SINCE); } catch (Exception e) { log.error("Exception while fetching If-Modified-Since: {}", e); @@ -154,7 +141,7 @@ public class CacheControl { */ lastModified = lastModified - (lastModified % 1000); - String ifNoneMatch = request.getHeader(HEADER_IF_NONE_MATCH); + String ifNoneMatch = request.getHeader(HeaderNames.HEADER_IF_NONE_MATCH); String eTag = controller.getETag(request); /** @@ -170,7 +157,7 @@ public class CacheControl { builder.append('"'); builder.append(eTag); builder.append('"'); - response.setHeader(HEADER_ETAG, builder.toString()); + response.setHeader(HeaderNames.HEADER_ETAG, builder.toString()); } @@ -204,7 +191,7 @@ public class CacheControl { ifNoneMatch = ifNoneMatch.substring(1, ifNoneMatch.length() - 1); } - if (!weak || (request.getMethod().equals("GET") && request.getHeader(HEADER_RANGE) == null)) { + if (!weak || (request.getMethod().equals("GET") && request.getHeader(HeaderNames.HEADER_RANGE) == null)) { /** * Die Gleichheit gilt nur, wenn die ETag's der Anfrage _und_ der * Antwort stark sind (starke Gleichheit!), oder wenn die Antwort nur @@ -225,7 +212,7 @@ public class CacheControl { log.debug("{}: first up!", url); /** HTTP/1.1-Caching-Header richtig setzen!! */ - response.setDateHeader(HEADER_LAST_MODIFIED, lastModified); + response.setDateHeader(HeaderNames.HEADER_LAST_MODIFIED, lastModified); /** Cache-Control für HTTP/1.1-Clients generieren */ Map cacheControl = new TreeMap(); @@ -248,7 +235,7 @@ public class CacheControl { * Expires-Header für HTTP/1.0-Clients setzen. */ cacheControl.put("max-age", Integer.toString(cacheSeconds)); - response.setDateHeader(HEADER_EXPIRES, (controller.getTimestamp() + (long) cacheSeconds * 1000)); + response.setDateHeader(HeaderNames.HEADER_EXPIRES, (controller.getTimestamp() + (long) cacheSeconds * 1000)); } /** Dem Handler die Gelegenheit geben, den Cache-Controll-Header anzupassen */ @@ -264,8 +251,8 @@ public class CacheControl { * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.32 * Abschnitt 14.32}) */ - response.setDateHeader(HEADER_EXPIRES, 0l); - response.addHeader(HEADER_PRAGMA, "no-cache"); + response.setDateHeader(HeaderNames.HEADER_EXPIRES, 0l); + response.addHeader(HeaderNames.HEADER_PRAGMA, "no-cache"); } StringBuilder builder = new StringBuilder(); @@ -276,7 +263,7 @@ public class CacheControl { builder.append('='); builder.append(entry.getValue()); } - response.addHeader(HEADER_CACHE_CONTROL, builder.toString()); + response.addHeader(HeaderNames.HEADER_CACHE_CONTROL, builder.toString()); } return true; @@ -296,14 +283,14 @@ public class CacheControl { } - interface CacheMethodHandle { + public interface CacheMethodHandle { long getTimestamp(); - int accepts(HttpServletRequest request) throws Exception; - int getCacheSeconds(HttpServletRequest request) throws Exception; - long getLastModified(HttpServletRequest request) throws Exception; - String getETag(HttpServletRequest request) throws Exception; + int accepts(HttpServletRequest request); + int getCacheSeconds(HttpServletRequest request); + long getLastModified(HttpServletRequest request); + String getETag(HttpServletRequest request); boolean isETagWeak(); - void cacheControl(HttpServletRequest request, Map cacheControlMap) throws Exception; + void cacheControl(HttpServletRequest request, Map cacheControlMap); } @@ -414,51 +401,63 @@ public class CacheControl { } @Override - public int accepts(HttpServletRequest request) - throws IllegalAccessException, - IllegalArgumentException, - InvocationTargetException - { - if (acceptsMethod == null) + public int accepts(HttpServletRequest request) throws IllegalArgumentException { + if (acceptsMethod == null) { return HttpServletResponse.SC_OK; - else - return (Integer)acceptsMethod.invoke(handler, request); + } + else { + try { + return (Integer)acceptsMethod.invoke(handler, request); + } + catch (Exception e) { + throw new IllegalArgumentException(e); + } + } } @Override - public int getCacheSeconds(HttpServletRequest request) - throws IllegalAccessException, - IllegalArgumentException, - InvocationTargetException - { - if (cacheSecondsMethod == null) + public int getCacheSeconds(HttpServletRequest request) throws IllegalArgumentException { + if (cacheSecondsMethod == null) { return cacheSeconds; - else - return (Integer)cacheSecondsMethod.invoke(handler, request); + } + else { + try { + return (Integer)cacheSecondsMethod.invoke(handler, request); + } + catch (Exception e) { + throw new IllegalArgumentException(e); + } + } } @Override - public long getLastModified(HttpServletRequest request) - throws IllegalAccessException, - IllegalArgumentException, - InvocationTargetException - { - if (lastModifiedMethod == null) + public long getLastModified(HttpServletRequest request) throws IllegalArgumentException { + if (lastModifiedMethod == null) { return lastModified; - else - return (Long)lastModifiedMethod.invoke(handler, request); + } + else { + try { + return (Long)lastModifiedMethod.invoke(handler, request); + } + catch (Exception e) { + throw new IllegalArgumentException(e); + } + } } @Override - public String getETag(HttpServletRequest request) - throws IllegalAccessException, - IllegalArgumentException, - InvocationTargetException - { - if (eTagMethod == null) + public String getETag(HttpServletRequest request) throws IllegalArgumentException { + if (eTagMethod == null) { return eTag; - else - return (String)eTagMethod.invoke(handler, request); + } + else { + try { + return (String)eTagMethod.invoke(handler, request); + } + catch (Exception e) { + throw new IllegalArgumentException(e); + } + } } @Override @@ -471,12 +470,16 @@ public class CacheControl { HttpServletRequest request, Map cacheControlMap ) - throws IllegalAccessException, - IllegalArgumentException, - InvocationTargetException + throws IllegalArgumentException { - if (cacheControlMethod != null) - cacheControlMethod.invoke(handler, request, cacheControlMap); + if (cacheControlMethod != null) { + try { + cacheControlMethod.invoke(handler, request, cacheControlMap); + } + catch (Exception e) { + throw new IllegalArgumentException(e); + } + } } } diff --git a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControlFilter.java b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControlFilter.java deleted file mode 100644 index 549f35ce..00000000 --- a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/CacheControlFilter.java +++ /dev/null @@ -1,209 +0,0 @@ -package de.halbekunst.juplo.cachecontrol; - -import java.io.IOException; -import java.io.PrintWriter; -import java.util.Locale; -import javax.servlet.Filter; -import javax.servlet.FilterChain; -import javax.servlet.FilterConfig; -import javax.servlet.ServletException; -import javax.servlet.ServletOutputStream; -import javax.servlet.ServletRequest; -import javax.servlet.ServletResponse; -import javax.servlet.http.Cookie; -import javax.servlet.http.HttpServletResponse; - -/** - * - * @author kai - */ -public class CacheControlFilter implements Filter { - - - @Override - public void init(FilterConfig filterConfig) throws ServletException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void destroy() { - throw new UnsupportedOperationException("Not supported yet."); - } - - - class HttpServletResponseWrapper implements HttpServletResponse { - - private final HttpServletResponse response; - - - HttpServletResponseWrapper(HttpServletResponse response) { - this.response = response; - } - - - @Override - public void addCookie(Cookie cookie) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public boolean containsHeader(String name) { - return response.containsHeader(name); - } - - @Override - public String encodeURL(String url) { - return response.encodeURL(url); - } - - @Override - public String encodeRedirectURL(String url) { - return response.encodeRedirectURL(url); - } - - @Override - public String encodeUrl(String url) { - return response.encodeUrl(url); - } - - @Override - public String encodeRedirectUrl(String url) { - return response.encodeRedirectUrl(url); - } - - @Override - public void sendError(int sc, String msg) throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void sendError(int sc) throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void sendRedirect(String location) throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setDateHeader(String name, long date) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void addDateHeader(String name, long date) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setHeader(String name, String value) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void addHeader(String name, String value) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setIntHeader(String name, int value) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void addIntHeader(String name, int value) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setStatus(int sc) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setStatus(int sc, String sm) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public String getCharacterEncoding() { - return response.getCharacterEncoding(); - } - - @Override - public String getContentType() { - return response.getContentType(); - } - - @Override - public ServletOutputStream getOutputStream() throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public PrintWriter getWriter() throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setCharacterEncoding(String charset) { - response.setCharacterEncoding(charset); - } - - @Override - public void setContentLength(int len) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setContentType(String type) { - response.setContentType(type); - } - - @Override - public void setBufferSize(int size) { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public int getBufferSize() { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void flushBuffer() throws IOException { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void resetBuffer() { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public boolean isCommitted() { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void reset() { - throw new UnsupportedOperationException("Not supported yet."); - } - - @Override - public void setLocale(Locale loc) { - response.setLocale(loc); - } - - @Override - public Locale getLocale() { - return response.getLocale(); - } - } -} diff --git a/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/HeaderNames.java b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/HeaderNames.java new file mode 100644 index 00000000..76736d28 --- /dev/null +++ b/cachecontrol/src/main/java/de/halbekunst/juplo/cachecontrol/HeaderNames.java @@ -0,0 +1,21 @@ +package de.halbekunst.juplo.cachecontrol; + +/** + * + * @author kai + */ +public abstract class HeaderNames { + + public static final String HEADER_ACCEPT_ENCODING = "Accept-Encoding"; + public static final String HEADER_CACHE_CONTROL = "Cache-Control"; + public static final String HEADER_CONTENT_ENCODING = "Content-Encoding"; + public static final String HEADER_DATE = "Date"; + public static final String HEADER_ETAG = "ETag"; + public static final String HEADER_EXPIRES = "Expires"; + public static final String HEADER_IF_MODIFIED_SINCE = "If-Modified-Since"; + public static final String HEADER_IF_NONE_MATCH = "If-None-Match"; + public static final String HEADER_LAST_MODIFIED = "Last-Modified"; + public static final String HEADER_PRAGMA = "Pragma"; + public static final String HEADER_RANGE = "Range"; + +} -- 2.20.1