#110 add RateLimiterUtil for RateLimiter customization

vjkit/src/main/java/com/vip/vjtools/vjkit/concurrent/RateLimiterUtil.java

@@ -0,0 +1,80 @@
+package com.vip.vjtools.vjkit.concurrent;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+
+import com.google.common.util.concurrent.RateLimiter;
+
+public class RateLimiterUtil {
+
+	/**
+	 * 一个用来定制RateLimiter的方法。默认装满token
+	 * 
+	 * @param permitsPerSecond 每秒允许的请求书，可看成QPS
+	 * @param maxBurstSeconds 最大的突发缓冲时间。用来应对突发流量。Guava的实现默认是1s。permitsPerSecond * maxBurstSeconds的数量，就是闲置时预留的缓冲token数量
+	 */
+	public static RateLimiter create(double permitsPerSecond, double maxBurstSeconds)
+			throws ReflectiveOperationException {
+		return create(permitsPerSecond, maxBurstSeconds, true);
+	}
+
+	/**
+	 * 一个用来定制RateLimiter的方法。
+	 * 
+	 * @param permitsPerSecond 每秒允许的请求书，可看成QPS
+	 * @param maxBurstSeconds 最大的突发缓冲时间。用来应对突发流量。Guava的实现默认是1s。permitsPerSecond * maxBurstSeconds的数量，就是闲置时预留的缓冲token数量
+	 * @param filledWithToken 是否需要创建时就保留有permitsPerSecond * maxBurstSeconds的token
+	 */
+	public static RateLimiter create(double permitsPerSecond, double maxBurstSeconds, boolean filledWithToken)
+			throws ReflectiveOperationException {
+		Class<?> sleepingStopwatchClass = Class
+				.forName("com.google.common.util.concurrent.RateLimiter$SleepingStopwatch");
+		Method createStopwatchMethod = sleepingStopwatchClass.getDeclaredMethod("createFromSystemTimer");
+		createStopwatchMethod.setAccessible(true);
+		Object stopwatch = createStopwatchMethod.invoke(null);
+
+		Class<?> burstyRateLimiterClass = Class
+				.forName("com.google.common.util.concurrent.SmoothRateLimiter$SmoothBursty");
+		Constructor<?> burstyRateLimiterConstructor = burstyRateLimiterClass.getDeclaredConstructors()[0];
+		burstyRateLimiterConstructor.setAccessible(true);
+
+		// set maxBurstSeconds
+		RateLimiter rateLimiter = (RateLimiter) burstyRateLimiterConstructor.newInstance(stopwatch, maxBurstSeconds);
+		rateLimiter.setRate(permitsPerSecond);
+
+		if (filledWithToken) {
+			// set storedPermits
+			setField(rateLimiter, "storedPermits", permitsPerSecond * maxBurstSeconds);
+		}
+
+		return rateLimiter;
+	}
+
+	private static boolean setField(Object targetObject, String fieldName, Object fieldValue) {
+		Field field;
+		try {
+			field = targetObject.getClass().getDeclaredField(fieldName);
+		} catch (NoSuchFieldException e) {
+			field = null;
+		}
+		Class superClass = targetObject.getClass().getSuperclass();
+		while (field == null && superClass != null) {
+			try {
+				field = superClass.getDeclaredField(fieldName);
+			} catch (NoSuchFieldException e) {
+				superClass = superClass.getSuperclass();
+			}
+		}
+		if (field == null) {
+			return false;
+		}
+		field.setAccessible(true);
+		try {
+			field.set(targetObject, fieldValue);
+			return true;
+		} catch (IllegalAccessException e) {
+			return false;
+		}
+	}
+}

vjkit/src/test/java/com/vip/vjtools/vjkit/concurrent/RateLimiterUtilTest.java

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+package com.vip.vjtools.vjkit.concurrent;
+
+import java.lang.reflect.Field;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.google.common.util.concurrent.RateLimiter;
+
+public class RateLimiterUtilTest {
+	@Test
+	public void testCreate() throws Exception {
+		RateLimiter rateLimiter = RateLimiterUtil.create(20000, 0.1);
+
+		Class superClass = rateLimiter.getClass().getSuperclass();
+		Field field = superClass.getDeclaredField("storedPermits");
+		field.setAccessible(true);
+
+		Assert.assertEquals(2000, (int) field.getDouble(rateLimiter));
+	}
+}