Google Guava BloomFilter

gistfile1.java

/*
 * Copyright (c) 2012-2013 www.iflytek.com. All Rights Reserved.
 * This software for customer relationship management system, developed by Ifly@ZY team.
 * Software code and design for the team, copy rights reserved.
 */

package com.ifkytek.irime;

import java.util.Set;

import com.google.common.base.Strings;
import com.google.common.collect.Sets;
import com.google.common.hash.BloomFilter;
import com.google.common.hash.Funnel;
import com.google.common.hash.PrimitiveSink;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

/**
 * <p>
 * 自定义Funner的布隆过滤器的处理.
 * </p>
 *
 * @author poplar.yfyang
 * @version 1.0 2013-01-26 11:36 AM
 * @since JDK 1.5
 */
public class BlootFilterFunnelTest {
	// email规则
	private static final String      EMAIL        = "^[a-zA-Z0-9]+([_.]?[a-zA-Z0-9])*@([a-zA-Z0-9]+\\.)+[a-zA-Z0-9]{2,3}$";
	/** 模拟数据容器 */
	private              Set<String> mail_list    = Sets.newHashSet();
	/** 不匹配的数据 */
	private              Set<String> no_mail_list = Sets.newHashSet();
	/** 布隆过滤器 */
	private BloomFilter<String> bloomFilter;

	/**
	 * 初始化数据
	 *
	 * @throws Exception 测试异常
	 */
	@Before
	public void setUp() throws Exception {
		for (int i = 1; i <= 10000; i++) {
			if (i % 2 == 0) {
				no_mail_list.add("iflytek" + i);
			} else {
				mail_list.add("iflytek" + i + "@iflytek.com");
			}
		}

	}

	@Test
	public void test_BlootFilter() throws Exception {
		//创建过滤器
		int size = mail_list.size();
		//注意第二个参数
		bloomFilter = BloomFilter.create(stringFunnel(), size);

		addStoredStringToBloomFilter();

		int falsePositiveCount = 0;
		for (String s : no_mail_list) {
			boolean mightContain = bloomFilter.mightContain(s);
			if (!mightContain) {
				System.out.println("no equal bloomFilter:" + s);
				falsePositiveCount++;
			}
		}

		Assert.assertEquals(falsePositiveCount,no_mail_list.size());

	}

	/** 将数据增加到布隆过滤器中 */
	private void addStoredStringToBloomFilter() {
		for (String email : mail_list) {
			bloomFilter.put(email);
		}
	}

	/**
	 * Returns a funnel that extracts the characters from a {@code CharSequence}.
	 */
	public static Funnel<String> stringFunnel() {
		return StringFunnel.INSTANCE;
	}

	/** 自定义Funnel */
	private enum StringFunnel implements Funnel<String> {

		INSTANCE;

		@Override
		public void funnel(String from, PrimitiveSink into) {
			//如果不是邮箱地址，则不进入Slink接收器
			if (isEmail(from)) {
				into.putString(from);
			}
		}

		/**
		 * 验证字符串是否为合法的Email （Email格式是指：字母、数字、下划线与'@'和'.'的组合，'@'数量不得超过1；连续两位字符不能为'_'
		 * 或'@'与'.'；不得以'@'或'.'或'_'开头；倒数第三位或第四位必须为'.'）
		 *
		 * @param email 要验证的字符串
		 * @return 验证通过返回 true，否则返回 false
		 */
		public boolean isEmail(String email) {
			return !Strings.isNullOrEmpty(email) && email.matches(EMAIL);
		}

	}
}