Implemented a Proposal for Automatic Content Negation and ETag Support (issues #3 and #5)

californium-core/src/main/java/org/eclipse/californium/core/CoapResource.java

@@ -20,6 +20,7 @@
 package org.eclipse.californium.core;
 
 import java.net.URI;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -33,14 +34,19 @@
 import org.eclipse.californium.core.coap.CoAP.Code;
 import org.eclipse.californium.core.coap.CoAP.ResponseCode;
 import org.eclipse.californium.core.coap.CoAP.Type;
+import org.eclipse.californium.core.coap.OptionSet;
 import org.eclipse.californium.core.coap.Response;
 import org.eclipse.californium.core.network.Endpoint;
 import org.eclipse.californium.core.network.Exchange;
 import org.eclipse.californium.core.observe.ObserveNotificationOrderer;
 import org.eclipse.californium.core.observe.ObserveRelation;
 import org.eclipse.californium.core.observe.ObserveRelationContainer;
 import org.eclipse.californium.core.server.ServerMessageDeliverer;
+import org.eclipse.californium.core.server.resources.AcceptDefaultSupport;
+import org.eclipse.californium.core.server.resources.AcceptSupport;
 import org.eclipse.californium.core.server.resources.CoapExchange;
+import org.eclipse.californium.core.server.resources.ETagDefaultSupport;
+import org.eclipse.californium.core.server.resources.ETagSupport;
 import org.eclipse.californium.core.server.resources.Resource;
 import org.eclipse.californium.core.server.resources.ResourceAttributes;
 import org.eclipse.californium.core.server.resources.ResourceObserver;
@@ -159,6 +165,12 @@ public  class CoapResource implements Resource {
 	/* The notification orderer. */
 	private ObserveNotificationOrderer notificationOrderer;
 
+	/* Support for ETags */
+	private ETagSupport etagSupport;
+
+	/* Support for Accept */
+	private AcceptSupport acceptSupport;
+
 	/**
 	 * Constructs a new resource with the specified name.
 	 *
@@ -184,8 +196,9 @@ public CoapResource(String name, boolean visible) {
 		this.observers = new CopyOnWriteArrayList<ResourceObserver>();
 		this.observeRelations = new ObserveRelationContainer();
 		this.notificationOrderer = new ObserveNotificationOrderer();
+		this.etagSupport = createETagSupport();
+		this.acceptSupport = createAcceptSupport();
 	}
-
 
 	/**
 	 * Handles any request in the given exchange. By default it responds
@@ -201,6 +214,13 @@ public CoapResource(String name, boolean visible) {
 	@Override
 	public void handleRequest(final Exchange exchange) {
 		Code code = exchange.getRequest().getCode();
+
+		if (code == Code.GET && validateETag(exchange))
+			return;
+
+		if (expectsUnacceptableFormat(exchange))
+			return;
+
 		switch (code) {
 			case GET:	handleGET(new CoapExchange(exchange, this)); break;
 			case POST:	handlePOST(new CoapExchange(exchange, this)); break;
@@ -209,6 +229,57 @@ public void handleRequest(final Exchange exchange) {
 		}
 	}
 
+	/**
+	 * Compares the ETags of the request with the current ETag from the
+	 * {@link ETagSupport}. If an ETag matches, the method automatically
+	 * responds with a 2.03 (Valid) and returns true. If there is no ETag or if
+	 * there is not ETagSupport object, the method returns false.
+	 *
+	 * @param exchange the exchange
+	 * @return true, if the request has a valid ETag, false otherwise
+	 */
+	public boolean validateETag(Exchange exchange) {
+		ETagSupport support = getETagSupport();
+		OptionSet options = exchange.getRequest().getOptions();
+		if (options.getETagCount() > 0 && support != null) {
+			byte[] current = support.getCurrentETag();
+			for (byte[] etag:options.getETags())
+				if (Arrays.equals(etag, current)) {
+					Response response = new Response(ResponseCode.VALID);
+					response.getOptions().addETag(current);
+					exchange.sendResponse(response);
+					return true;
+				}
+		}
+		return false;
+	}
+
+	/**
+	 * Compares the accept value of the request with the accept values of the
+	 * AcceptSupport object (ASO). If the request has no accept value, it is
+	 * considered to accept anything. If there is no ASO, the resource is
+	 * considered to accept any request (it still can send a Not-Acceptable
+	 * response). Only if the request has an accept value and the ASO does not
+	 * accept it, this method responds with a 4.06 (Not Acceptable) and returns
+	 * true. The {@link AcceptDefaultSupport} by default accepts everything.
+	 *
+	 * @param exchange the exchange
+	 * @return true, if the request does NOT accept the content format of this
+	 *         resource
+	 */
+	public boolean expectsUnacceptableFormat(Exchange exchange) {
+		AcceptSupport support = getAcceptSupport();
+		OptionSet options = exchange.getRequest().getOptions();
+		if (options.hasAccept() && support != null) {
+			if (! support.isAcceptable(options.getAccept())) {
+				Response response = new Response(ResponseCode.NOT_ACCEPTABLE);
+				exchange.sendResponse(response);
+				return true;
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Handles the GET request in the given CoAPExchange. By default it
 	 * responds with a 4.05 (Method Not Allowed). Override this method to
@@ -677,7 +748,7 @@ public void removeObserveRelation(ObserveRelation relation) {
 	}
 
 	/**
-	 * Returns the number of observe realtions that this resource has to CoAP
+	 * Returns the number of observe relations that this resource has to CoAP
 	 * clients.
 	 * 
 	 * @return the observer count
@@ -718,6 +789,60 @@ protected void notifyObserverRelations() {
 			relation.notifyObservers();
 		}
 	}
+
+	/**
+	 * Creates a new ETagSupport object.
+	 * 
+	 * @return an ETagSupport object
+	 */
+	protected ETagSupport createETagSupport() {
+		return new ETagDefaultSupport();
+	}
+
+	/**
+	 * Creates a new AcceptSupport object.
+	 * 
+	 * @return an AcceptSupport object
+	 */
+	protected AcceptSupport createAcceptSupport() {
+		return new AcceptDefaultSupport();
+	}
+
+	/**
+	 * Gets the ETagSupport object or null if none is present.
+	 *
+	 * @return the ETagSupport object
+	 */
+	public ETagSupport getETagSupport() {
+		return etagSupport;
+	}
+
+	/**
+	 * Sets the ETag support object.
+	 *
+	 * @param support the new ETag support object
+	 */
+	public void setETagSupport(ETagSupport support) {
+		this.etagSupport = support;
+	}
+
+	/**
+	 * Gets the AcceptSupport object or null if none is present.
+	 * 
+	 * @return the AcceptSupport object
+	 */
+	public AcceptSupport getAcceptSupport() {
+		return acceptSupport;
+	}
+
+	/**
+	 * Sets the accept support object.
+	 *
+	 * @param support the new accept support obejct
+	 */
+	public void setAcceptSupport(AcceptSupport support) {
+		this.acceptSupport = support;
+	}
 
 	/* (non-Javadoc)
 	 * @see org.eclipse.californium.core.server.resources.Resource#getChildren()

californium-core/src/main/java/org/eclipse/californium/core/server/resources/AcceptDefaultSupport.java

@@ -0,0 +1,54 @@
+package org.eclipse.californium.core.server.resources;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+/**
+ * The default implementation for supporting accept options in resources. An
+ * instance of AcceptDefaultSupport contains a set with all acceptable content
+ * formats. <b>If it holds no value at all, then ALL content formats are
+ * considered accepted</b>.
+ */
+public class AcceptDefaultSupport implements AcceptSupport {
+
+	/** The acceptable content formats. */
+	private Set<Integer> acceptables;
+
+	/**
+	 * Instantiates a support object for accept options.
+	 */
+	public AcceptDefaultSupport() {
+		acceptables = new CopyOnWriteArraySet<Integer>();
+	}
+
+	/* (non-Javadoc)
+	 * @see org.eclipse.californium.core.server.resources.AcceptSupport#addAcceptable(int)
+	 */
+	public void addAcceptable(int... acceptableValues) {
+		for (int acc:acceptableValues)
+			acceptables.add(acc);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.eclipse.californium.core.server.resources.AcceptSupport#removeAcceptable(int)
+	 */
+	public void removeAcceptable(int... values) {
+		for (int val:values)
+			acceptables.remove(val);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.eclipse.californium.core.server.resources.AcceptSupport#accepts(int)
+	 */
+	public boolean isAcceptable(int acceptable) {
+		return acceptables.isEmpty() || acceptables.contains(acceptable);
+	}
+
+	/* (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
+	@Override
+	public String toString() {
+		return "AcceptDefaultSupport("+acceptables.toString()+")";
+	}
+}

californium-core/src/main/java/org/eclipse/californium/core/server/resources/AcceptSupport.java

@@ -0,0 +1,32 @@
+package org.eclipse.californium.core.server.resources;
+
+/**
+ * An AcceptSupport object supports a resource in checking if the requested
+ * content format (accept option) of a request is consistent with the content
+ * format(s) the resource provides.
+ */
+public interface AcceptSupport {
+
+	/**
+	 * Adds the specified values to the acceptable content format requests.
+	 *
+	 * @param acceptableValues the acceptable values
+	 */
+	public void addAcceptable(int... acceptableValues);
+
+	/**
+	 * Removes the specified values from the acceptable content format requests.
+	 *
+	 * @param values the values
+	 */
+	public void removeAcceptable(int... values);
+
+	/**
+	 * Returns true if the specified content format can be provided.
+	 *
+	 * @param acceptable the requested content format
+	 * @return true, if the accept request can be met
+	 */
+	public boolean isAcceptable(int acceptable);
+
+}