Add Refreshable, easier way to use AutoRefreshingReference

src/main/java/org/cobbzilla/util/cache/AutoRefreshingReference.java

@@ -7,6 +7,10 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import static org.cobbzilla.util.daemon.ZillaRuntime.now;
 
+// Wraps an AtomicReference and presents a similar 'get' method, but will refresh the underlying
+// object via the 'refresh' method if it is null or stale.
+//
+// Consider using Refreshable, a subclass with a more functional approach
 public abstract class AutoRefreshingReference<T> {
 
     @Getter private final AtomicReference<T> object = new AtomicReference<>();

src/main/java/org/cobbzilla/util/cache/BackgroundRefreshable.java

@@ -0,0 +1,28 @@
+package org.cobbzilla.util.cache;
+
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.concurrent.Callable;
+import java.util.function.Function;
+
+@Slf4j
+public class BackgroundRefreshable<T> extends BackgroundRefreshingReference<T> {
+
+    @Getter private final String name;
+    @Getter private final long timeout;
+    @Getter private final Callable<T> refresher;
+    @Getter private final Function<Exception, T> errorRefreshing;
+
+    public BackgroundRefreshable(String name, long timeout, Callable<T> refresher) { this(name, timeout, refresher, e -> null); }
+
+    public BackgroundRefreshable(String name, long timeout, Callable<T> refresher, Function<Exception, T> errorRefreshing) {
+        this.name = name;
+        this.timeout = timeout;
+        this.refresher = refresher;
+        this.errorRefreshing = errorRefreshing;
+    }
+
+    @Override public T refresh() { return Refreshable.refresh(name, refresher, errorRefreshing); }
+
+}

src/main/java/org/cobbzilla/util/cache/Refreshable.java

@@ -0,0 +1,45 @@
+package org.cobbzilla.util.cache;
+
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.concurrent.Callable;
+import java.util.function.Function;
+
+import static org.cobbzilla.util.daemon.ZillaRuntime.die;
+import static org.cobbzilla.util.daemon.ZillaRuntime.shortError;
+
+@Slf4j
+public class Refreshable<T> extends AutoRefreshingReference<T> {
+
+    @Getter private final String name;
+    @Getter private final long timeout;
+    @Getter private final Callable<T> refresher;
+    @Getter private final Function<Exception, T> errorRefreshing;
+
+    public Refreshable(String name, long timeout, Callable<T> refresher) { this(name, timeout, refresher, e -> null); }
+
+    public Refreshable(String name, long timeout, Callable<T> refresher, Function<Exception, T> errorRefreshing) {
+        this.name = name;
+        this.timeout = timeout;
+        this.refresher = refresher;
+        this.errorRefreshing = errorRefreshing;
+    }
+
+    @Override public T refresh() { return refresh(name, refresher, errorRefreshing); }
+
+    public static <T> T refresh(String name, Callable<T> refresher, Function<Exception,T> errorRefreshing) {
+        try {
+            return refresher.call();
+        } catch (Exception e) {
+            final String msg = "refresh(" + name + "): " + shortError(e);
+            log.error(msg);
+            try {
+                return errorRefreshing.apply(e);
+            } catch (Exception ex) {
+                return die("refresh("+name+") failed with: "+shortError(e)+", and then errorRefreshing failed with "+shortError(ex));
+            }
+        }
+    }
+
+}