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.Inject;
008 import de.deepamehta.core.service.event.ServiceRequestFilterListener;
009 import de.deepamehta.core.service.event.ServiceResponseFilterListener;
010
011 // ### TODO: hide Jersey internals. Move to JAX-RS 2.0.
012 import com.sun.jersey.spi.container.ContainerRequest;
013 import com.sun.jersey.spi.container.ContainerResponse;
014
015 import javax.ws.rs.WebApplicationException;
016 import javax.ws.rs.core.MultivaluedMap;
017 import javax.ws.rs.core.Response;
018
019 import java.util.Date;
020 import java.util.logging.Logger;
021 import java.util.regex.Matcher;
022 import java.util.regex.Pattern;
023
024
025
026 public class CachingPlugin extends PluginActivator implements ServiceRequestFilterListener,
027 ServiceResponseFilterListener {
028
029 // ------------------------------------------------------------------------------------------------------- Constants
030
031 private static String CACHABLE_PATH = "core/(topic|association)/(\\d+)";
032
033 private static String HEADER_CACHE_CONTROL = "Cache-Control";
034
035 // ---------------------------------------------------------------------------------------------- Instance Variables
036
037 @Inject
038 private TimeService timeService;
039
040 private Pattern cachablePath = Pattern.compile(CACHABLE_PATH);
041
042 private Logger logger = Logger.getLogger(getClass().getName());
043
044 // -------------------------------------------------------------------------------------------------- Public Methods
045
046
047
048 // ********************************
049 // *** Listener Implementations ***
050 // ********************************
051
052
053
054 @Override
055 public void serviceRequestFilter(ContainerRequest request) {
056 // ### TODO: optimization. Retrieving and instantiating an entire DeepaMehtaObject just to query its timestamp
057 // might be inefficient. Knowing the sole object ID should be sufficient. However, this would require extending
058 // the Time API and in turn the Core Service API by ID-based property getter methods.
059 DeepaMehtaObject object = requestObject(request);
060 if (object != null) {
061 if (timeService == null) {
062 throw new RuntimeException("Time service is not available");
063 }
064 //
065 long time = timeService.getModificationTime(object);
066 Response.ResponseBuilder response = request.evaluatePreconditions(new Date(time));
067 if (response != null) {
068 logger.info("### Precondition of " + request.getMethod() + " request failed (object " +
069 object.getId() + ")");
070 throw new WebApplicationException(response.build());
071 }
072 }
073 }
074
075 @Override
076 public void serviceResponseFilter(ContainerResponse response) {
077 DeepaMehtaObject object = responseObject(response);
078 if (object != null) {
079 setCacheControlHeader(response, "max-age=0");
080 }
081 }
082
083
084
085 // ------------------------------------------------------------------------------------------------- Private Methods
086
087 private DeepaMehtaObject requestObject(ContainerRequest request) {
088 // Example URL: "http://localhost:8080/core/topic/2695?include_childs=true"
089 // request.getBaseUri()="http://localhost:8080/"
090 // request.getPath()="core/topic/2695"
091 // request.getAbsolutePath()="http://localhost:8080/core/topic/2695"
092 // request.getRequestUri()="http://localhost:8080/core/topic/2695?include_childs=true"
093 Matcher m = cachablePath.matcher(request.getPath());
094 if (m.matches()) {
095 String objectType = m.group(1); // group 1 is "topic" or "association"
096 long objectId = Long.parseLong(m.group(2));
097 if (objectType.equals("topic")) {
098 return dms.getTopic(objectId);
099 } else if (objectType.equals("association")) {
100 return dms.getAssociation(objectId);
101 } else {
102 throw new RuntimeException("Unexpected object type: \"" + objectType + "\"");
103 }
104 } else {
105 return null;
106 }
107 }
108
109 // ---
110
111 // ### FIXME: copy in TimePlugin
112 private DeepaMehtaObject responseObject(ContainerResponse response) {
113 Object entity = response.getEntity();
114 return entity instanceof DeepaMehtaObject ? (DeepaMehtaObject) entity : null;
115 }
116
117 private void setCacheControlHeader(ContainerResponse response, String value) {
118 setHeader(response, HEADER_CACHE_CONTROL, value);
119 }
120
121 // ### FIXME: copy in TimePlugin
122 private void setHeader(ContainerResponse response, String header, String value) {
123 MultivaluedMap headers = response.getHttpHeaders();
124 //
125 if (headers.containsKey(header)) {
126 throw new RuntimeException("Response already has a \"" + header + "\" header");
127 }
128 //
129 headers.putSingle(header, value);
130 }
131 }