redis lua scripting

Author: Vitalii Cherkashyn

redis/lua-script.java.snippet

@@ -0,0 +1,27 @@
+public class UpdateScript {
+    private final Jedis jedis;
+    private final String sha;
+    private final static String script =
+            "local key = KEYS[1] " +
+            "local new = ARGV[1] " +
+            "local current = redis.call('GET', key) " +
+            "if (current == false) or " +
+            "   (tonumber(new) < tonumber(current)) then " +
+            "  redis.call('SET', key, new) " +
+            "  return 1 " +
+            "else " +
+            "  return 0 " +
+            "end";
+
+    public UpdateIfLowestScript(Jedis jedis) {
+        this.jedis = jedis;
+        this.sha = jedis.scriptLoad(script);
+    }
+
+    public boolean updateIfLowest(String key, Integer newValue) {
+        List<String> keys = Collections.singletonList(key);
+        List<String> args = Collections.singletonList(String.valueOf(newValue));
+        Object response = jedis.evalsha(sha, keys, args);
+        return (Long)response == 1;
+    }
+}