Error

[2018-05-02 18:28:01,562] ERROR - APIAuthenticationHandler API authentication failure due to Unclassified Authentication Failure
org.wso2.carbon.apimgt.gateway.handlers.security.APISecurityException: Error while accessing backend services for API key validation
	at org.wso2.carbon.apimgt.gateway.handlers.security.keys.WSAPIKeyDataStore.getAllURITemplates(WSAPIKeyDataStore.java:77)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIKeyValidator.getAllURITemplates(APIKeyValidator.java:772)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIKeyValidator.doGetAPIInfo(APIKeyValidator.java:626)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIKeyValidator.findMatchingVerb(APIKeyValidator.java:566)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIKeyValidator.getResourceAuthenticationScheme(APIKeyValidator.java:359)
	at org.wso2.carbon.apimgt.gateway.handlers.security.oauth.OAuthAuthenticator.authenticate(OAuthAuthenticator.java:119)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIAuthenticationHandler.isAuthenticate(APIAuthenticationHandler.java:188)
	at org.wso2.carbon.apimgt.gateway.handlers.security.APIAuthenticationHandler.handleRequest(APIAuthenticationHandler.java:126)
	at org.apache.synapse.rest.API.process(API.java:325)
	at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:90)
	at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:69)
	at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:304)
	at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:78)
	at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
	at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:330)
	at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:159)
	at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: org.wso2.carbon.apimgt.gateway.handlers.security.APISecurityException: Error while accessing backend services for API key validation
	at org.wso2.carbon.apimgt.gateway.handlers.security.keys.APIKeyValidatorClient.getAllURITemplates(APIKeyValidatorClient.java:163)
	at org.wso2.carbon.apimgt.gateway.handlers.security.keys.WSAPIKeyDataStore.getAllURITemplates(WSAPIKeyDataStore.java:75)
	... 19 more
Caused by: java.lang.NullPointerException
	at org.wso2.carbon.apimgt.gateway.handlers.security.keys.APIKeyValidatorClient.getAllURITemplates(APIKeyValidatorClient.java:157)
	... 20 more