Add a filter to chean the cache frequently

Add TimedCacheCleanerFilter class to clean the nesstar api cache every 10 minutes
And the expirationTimeout can also be configured in config.yaml, default value is 600 seconds
Fixes #2640

README.md

@@ -7,7 +7,7 @@ Getting Started
 ---------------
 
 1. Run `mvn package` to build everything
-1. Copy the `config.yaml.example` to `config.yaml` and edit it to add your own server URI and logon credentials.
+1. Copy the `config.yaml.example` to `config.yaml` and edit it to add your own server URI, logon credentials and some configuration options like interval of clean cache.
 1. Run `java -jar target/nesstar_rest_api-0.4.0.jar server config.yaml`
 
 Note: The name of the JAR file may change. See the `target` folder.

config.yaml.example

 serverURI: http://my-example.com
 userId: myUser
 password: s3cret-p4ssw0rd
+expirationTimeout: 600 //the interval of clean cache, default value is 600 second

src/main/java/com/nesstar/rest/NesstarDropConfiguration.java

@@ -10,6 +10,7 @@ public final class NesstarDropConfiguration extends Configuration {
    private String serverURI;
    private String userId;
    private String password;
+   private String expirationTimeout;
 
    public String getServerURI() {
       return serverURI;
@@ -22,4 +23,6 @@ public final class NesstarDropConfiguration extends Configuration {
    public String getPassword() {
       return password;
    }
+
+   public String getExpirationTimeout() {return expirationTimeout;}
 }

src/main/java/com/nesstar/rest/NesstarDropService.java

 package com.nesstar.rest;
 
-import com.nesstar.rest.filters.TabulationEntityTagFilter;
-import com.nesstar.rest.filters.ManualJettyAllowWildcardOriginFilter;
-import com.nesstar.rest.filters.CorrelationEntityTagFilter;
-import com.nesstar.rest.filters.EntityTagFilter;
-import com.nesstar.rest.filters.CubeEntityTagFilter;
-import com.nesstar.rest.filters.RegressionEntityTagFilter;
-import com.nesstar.rest.filters.LanguageFilter;
-import com.nesstar.rest.filters.CommonEntityTagFilter;
+import com.nesstar.rest.filters.*;
 import com.nesstar.rest.resources.SearchResource;
 import org.eclipse.jetty.server.session.SessionHandler;
 import org.eclipse.jetty.servlets.CrossOriginFilter;
@@ -67,6 +60,9 @@ public  class NesstarDropService extends Service<NesstarDropConfiguration> {
 
       environment.addHealthCheck(new NesstarHealthCheck(serverHandler));
 
+      TimedCacheCleanerFilter timedCacheCleanerFilter = new TimedCacheCleanerFilter(configuration.getExpirationTimeout());
+      environment.addFilter(timedCacheCleanerFilter, "/*");
+
       environment.addFilter(CrossOriginFilter.class, "/*")
                  .setInitParam(CrossOriginFilter.ALLOWED_HEADERS_PARAM, "X-Requested-With,Content-Type,Accept,Origin");
 

src/main/java/com/nesstar/rest/filters/TimedCacheCleanerFilter.java

+package com.nesstar.rest.filters;
+
+import com.nesstar.api.NesstarDBFactory;
+import javax.servlet.Filter;
+import javax.servlet.FilterConfig;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.ServletException;
+import java.io.IOException;
+import java.util.Date;
+
+public class TimedCacheCleanerFilter implements Filter {
+    private static long latestTimeStamp = 0;
+    private int EXPIRATION_TIMEOUT = 600 * 1000;
+
+    public TimedCacheCleanerFilter (String expirationTimeout) {
+        if (expirationTimeout != null) {
+            try {
+                this.EXPIRATION_TIMEOUT = Integer.parseInt(expirationTimeout) * 1000;
+            } catch (NumberFormatException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    public synchronized void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
+        //Check timestamp of cache
+        Date currentTime = new Date();
+
+        if (currentTime.getTime() - latestTimeStamp > this.EXPIRATION_TIMEOUT) {
+            this.latestTimeStamp = currentTime.getTime();
+            //If cache is old, clear
+            NesstarDBFactory.getInstance().clear();
+        }
+
+        chain.doFilter(request, response);
+    }
+
+    public void init(FilterConfig arg0) throws ServletException { }
+
+    public void destroy() { }
+}
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