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-------------------------");
}
}
