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redis 樂觀鎖實踐秒殺

高洛峰

Nov 22, 2016 pm 05:51 PM

redis

需求：有一個標(理解成搶紅包也行，accountBalance預賦值1000元)，大家可以搶購，每個用戶搶購成功後，更新最後標的總數，在並發情況下，使用redis的樂觀鎖，保證更新標總值正確性，先往redis放一個標的金額：

set accountBalance "1000"

實作方式如下：

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>mybatisPage</groupId>
	<artifactId>page</artifactId>
	<version>1.0-SNAPSHOT</version>
	<packaging>war</packaging>

	<name>PageHelperSample</name>
	<url>http://git.oschina.net/free/Mybatis-Sample</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<!-- jstl -->
		<dependency>
			<groupId>jstl</groupId>
			<artifactId>jstl</artifactId>
			<version>1.1.2</version>
		</dependency>
		<dependency>
			<groupId>taglibs</groupId>
			<artifactId>standard</artifactId>
			<version>1.1.2</version>
		</dependency>
		<!-- jstl -->
		<dependency>
			<groupId>commons-pool</groupId>
			<artifactId>commons-pool</artifactId>
			<version>1.6</version>
		</dependency>

		<!-- log mybatis sql -->
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>1.7.5</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>1.7.5</version>
		</dependency>
		<!-- log mybatis sql -->

		<!-- fastjson -->
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.5</version>
		</dependency>
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.4</version>
		</dependency>
		<!-- web -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>servlet-api</artifactId>
			<version>2.5</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>jsp-api</artifactId>
			<version>2.1</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>taglibs</groupId>
			<artifactId>standard</artifactId>
			<version>1.1.2</version>
		</dependency>
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>

		<dependency>
			<groupId>com.github.pagehelper</groupId>
			<artifactId>pagehelper</artifactId>
			<version>3.7.4</version>
		</dependency>
		<dependency>
			<groupId>com.github.jsqlparser</groupId>
			<artifactId>jsqlparser</artifactId>
			<version>0.9.1</version>
		</dependency>

		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.11</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>
		<dependency>
			<groupId>org.mybatis</groupId>
			<artifactId>mybatis</artifactId>
			<version>3.2.5</version>
		</dependency>
		<!-- util -->
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-lang3</artifactId>
			<version>3.1</version>
		</dependency>
		<!-- mysql -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.35</version>
		</dependency>
		<!-- redis -->
		<dependency>
			<groupId>redis.clients</groupId>
			<artifactId>jedis</artifactId>
			<version>2.1.0</version>
			<type>jar</type>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.6</source>
					<target>1.6</target>
					<encoding>utf-8</encoding>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.mortbay.jetty</groupId>
				<artifactId>jetty-maven-plugin</artifactId>
				<version>8.0.0.M3</version>
			</plugin>
		</plugins>
	</build></project>

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
	version="3.0">
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
	
	<servlet>
		<servlet-name>bid</servlet-name>
		<servlet-class>com.heli.mybatis.page.servlet.ReidsMatchServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>bid</servlet-name>
		<url-pattern>/bid</url-pattern>
	</servlet-mapping>
	<servlet>
		<servlet-name>list</servlet-name>
		<servlet-class>com.heli.mybatis.page.servlet.ReidsMatchListServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>list</servlet-name>
		<url-pattern>/list</url-pattern>
	</servlet-mapping></web-app>

servlet bid.jsp

package com.heli.mybatis.page.servlet;

import java.io.IOException;
import java.util.List;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang3.StringUtils;

import com.commnon.RedisAPI;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;

public class ReidsMatchServlet extends HttpServlet {
	public static JedisPool pool = RedisAPI.getPool();

	// RedisAPI.set("accountBalance", "999999999");// 标还剩999999999块钱

	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		Jedis jedis = pool.getResource();
		long start = System.currentTimeMillis();
		int flag = 0;
		try {
			flag = bid(request, response, jedis);
		} catch (Exception e) {
			e.printStackTrace();
			response.getWriter().write("fail buy");
		} finally {
			pool.returnBrokenResource(jedis);
			RedisAPI.returnResource(pool, jedis);
		}
		if (flag == 1) {
			response.getWriter().write("success buy");
		} else if (flag == 2) {
			response.getWriter().write("have buy");
		} else if (flag == 0) {
			response.getWriter().write("bid is zero ,you can not buy");
		}else{
			response.getWriter().write("fail buy");
		}
		long end = System.currentTimeMillis();
		System.out.println("--------------------------------------------请求耗时：" + (end - start) + "毫秒");
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

	private int bid(HttpServletRequest request, HttpServletResponse response, Jedis jedis) throws Exception {
		int flag = 0;// 1,成功,2已经购买，3已经没钱了，其他異常
		// 每个请求对应一个userId
		int userId = new Random().nextInt(999999);
		
		// 观察 总标值，每人抢购一元
		while ("OK".equals(jedis.watch("accountBalance"))) {
        		// 判断是否购买过
        		Boolean isBuy = RedisAPI.sismember("userIdSet", userId + "");
        		if (isBuy) {
        			flag = 2;
        			return flag;
        		}
        		//投资额
			int r = 1;// new Random().nextInt(2);
			int lastAccount = 0;
			String balance = RedisAPI.get("accountBalance");
			if (StringUtils.isNotBlank(balance)) {
				lastAccount = Integer.valueOf(balance) - r;
			}
			if (lastAccount < 0) {
				flag = 3;
				break;
			}
			Transaction tx = jedis.multi();
			tx.set("accountBalance", lastAccount + "");
			List<Object> result = tx.exec();
			if (result == null || result.isEmpty()) {
				jedis.unwatch();
			} else {
				System.out.println("恭喜您，" + userId + "已经中标" + r + "元，标余额" + lastAccount + "元");
				RedisAPI.set(Thread.currentThread().getName(), r + "");
				RedisAPI.sadd("userIdSet", userId + "");
				flag = 1;
				break;
			}
		}
		return flag;
	}
}

list.jsp

package com.heli.mybatis.page.servlet;

import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.commnon.RedisAPI;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;

public class ReidsMatchListServlet extends HttpServlet {
	public static JedisPool pool= RedisAPI.getPool();;
	public static Jedis jedis;
	static {
		jedis = pool.getResource();
	}

	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		list(request, response);
		try {
			response.sendRedirect("list.jsp");
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

	private void list(HttpServletRequest request, HttpServletResponse response) {
		Set set = jedis.smembers("userIdSet");
		Iterator ite = set.iterator();
		System.out.println("中标名单-------------------------");
		int i = 0;
		Map<String, String> map = new HashMap<String, String>();
		while (ite.hasNext()) {
			i++;
			Object obj1 = ite.next();
			System.out.println("第" + i + "名：" + obj1);
			map.put("第" + i + "名：", obj1 + "");
		}
		request.getSession().setAttribute("user", map);
		System.out.println("中标名单-------------------------");
	}

}

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