001 package de.deepamehta.plugins.caching;
002
003 import de.deepamehta.plugins.time.service.TimeService;
004
005 import de.deepamehta.core.DeepaMehtaObject;
006 import de.deepamehta.core.osgi.PluginActivator;
007 import de.deepamehta.core.service.PluginService;
008 import de.deepamehta.core.service.annotation.ConsumesService;
009 import de.deepamehta.core.service.event.ServiceRequestFilterListener;
010 import de.deepamehta.core.service.event.ServiceResponseFilterListener;
011
012 // ### TODO: hide Jersey internals. Move to JAX-RS 2.0.
013 import com.sun.jersey.spi.container.ContainerRequest;
014 import com.sun.jersey.spi.container.ContainerResponse;
015
016 import javax.ws.rs.WebApplicationException;
017 import javax.ws.rs.core.MultivaluedMap;
018 import javax.ws.rs.core.Response;
019
020 import java.util.Date;
021 import java.util.logging.Logger;
022 import java.util.regex.Matcher;
023 import java.util.regex.Pattern;
024
025
026
027 public class CachingPlugin extends PluginActivator implements ServiceRequestFilterListener,
028 ServiceResponseFilterListener {
029
030 // ------------------------------------------------------------------------------------------------------- Constants
031
032 private static String CACHABLE_PATH = "core/(topic|association)/(\\d+)";
033
034 private static String HEADER_CACHE_CONTROL = "Cache-Control";
035
036 // ---------------------------------------------------------------------------------------------- Instance Variables
037
038 private TimeService timeService;
039 private Pattern cachablePath = Pattern.compile(CACHABLE_PATH);
040
041 private Logger logger = Logger.getLogger(getClass().getName());
042
043 // -------------------------------------------------------------------------------------------------- Public Methods
044
045
046
047 // ****************************
048 // *** Hook Implementations ***
049 // ****************************
050
051
052
053 @Override
054 @ConsumesService("de.deepamehta.plugins.time.service.TimeService")
055 public void serviceArrived(PluginService service) {
056 timeService = (TimeService) service;
057 }
058
059 @Override
060 public void serviceGone(PluginService service) {
061 timeService = null;
062 }
063
064
065
066 // ********************************
067 // *** Listener Implementations ***
068 // ********************************
069
070
071
072 @Override
073 public void serviceRequestFilter(ContainerRequest request) {
074 // ### TODO: optimization. Retrieving and instantiating an entire DeepaMehtaObject just to query its timestamp
075 // might be inefficient. Knowing the sole object ID should be sufficient. However, this would require extending
076 // the Time API and in turn the Core Service API by ID-based property getter methods.
077 DeepaMehtaObject object = requestObject(request);
078 if (object != null) {
079 long time = timeService.getModificationTime(object);
080 Response.ResponseBuilder response = request.evaluatePreconditions(new Date(time));
081 if (response != null) {
082 logger.info("### Precondition of " + request.getMethod() + " request failed (object " +
083 object.getId() + ")");
084 throw new WebApplicationException(response.build());
085 }
086 }
087 }
088
089 @Override
090 public void serviceResponseFilter(ContainerResponse response) {
091 DeepaMehtaObject object = responseObject(response);
092 if (object != null) {
093 setCacheControlHeader(response, "max-age=0");
094 }
095 }
096
097
098
099 // ------------------------------------------------------------------------------------------------- Private Methods
100
101 private DeepaMehtaObject requestObject(ContainerRequest request) {
102 // Example URL: "http://localhost:8080/core/topic/2695?fetch_composite=false"
103 // request.getBaseUri()="http://localhost:8080/"
104 // request.getPath()="core/topic/2695"
105 // request.getAbsolutePath()="http://localhost:8080/core/topic/2695"
106 // request.getRequestUri()="http://localhost:8080/core/topic/2695?fetch_composite=false"
107 Matcher m = cachablePath.matcher(request.getPath());
108 if (m.matches()) {
109 String objectType = m.group(1); // group 1 is "topic" or "association"
110 long objectId = Long.parseLong(m.group(2));
111 if (objectType.equals("topic")) {
112 return dms.getTopic(objectId, false);
113 } else if (objectType.equals("association")) {
114 return dms.getAssociation(objectId, false);
115 } else {
116 throw new RuntimeException("Unexpected object type: \"" + objectType + "\"");
117 }
118 } else {
119 return null;
120 }
121 }
122
123 // ---
124
125 // ### FIXME: copy in TimePlugin
126 private DeepaMehtaObject responseObject(ContainerResponse response) {
127 Object entity = response.getEntity();
128 return entity instanceof DeepaMehtaObject ? (DeepaMehtaObject) entity : null;
129 }
130
131 private void setCacheControlHeader(ContainerResponse response, String directives) {
132 setHeader(response, HEADER_CACHE_CONTROL, directives);
133 }
134
135 // ### FIXME: copy in TimePlugin
136 private void setHeader(ContainerResponse response, String header, String value) {
137 MultivaluedMap headers = response.getHttpHeaders();
138 //
139 if (headers.containsKey(header)) {
140 throw new RuntimeException("Response already has a \"" + header + "\" header");
141 }
142 //
143 headers.putSingle(header, value);
144 }
145 }