1 import java.math.BigInteger;  2 import java.util.ArrayList;  3 import java.util.HashMap;  4 import java.util.List;  5 import java.util.Map;  6 import java.util.Map.Entry;  7   8 /**  9  * 权重轮询调度算法(WeightedRound-RobinScheduling)-Java实现 10  * @author huligong 11  * */ 12 public class WeightedRoundRobinScheduling { 13  14     private int currentIndex = -1;// 上一次选择的服务器 15     private int currentWeight = 0;// 当前调度的权值 16     private int maxWeight = 0; // 最大权重 17     private int gcdWeight = 0; //所有服务器权重的最大公约数 18     private int serverCount = 0; //服务器数量 19     private List<Server> serverList; //服务器集合 20  21     /** 22      * 返回最大公约数 23      * @param a 24      * @param b 25      * @return 26      */ 27     private static int gcd(int a, int b) { 28         BigInteger b1 = new BigInteger(String.valueOf(a)); 29         BigInteger b2 = new BigInteger(String.valueOf(b)); 30         BigInteger gcd = b1.gcd(b2); 31         return gcd.intValue(); 32     } 33      34       35     /** 36      * 返回所有服务器权重的最大公约数 37      * @param serverList 38      * @return 39      */ 40     private static int getGCDForServers(List<Server> serverList ) { 41         int w = 0; 42         for (int i = 0, len = serverList.size(); i < len - 1; i++) { 43             if (w == 0) { 44                 w = gcd(serverList.get(i).weight, serverList.get(i + 1).weight); 45             } else { 46                 w = gcd(w, serverList.get(i + 1).weight); 47             } 48         } 49         return w; 50     } 51      52  53     /** 54      * 返回所有服务器中的最大权重 55      * @param serverList 56      * @return 57      */ 58     public static int getMaxWeightForServers(List<Server> serverList) { 59         int w = 0; 60         for (int i = 0, len = serverList.size(); i < len - 1; i++) { 61             if (w == 0) { 62                 w = Math.max(serverList.get(i).weight, serverList.get(i + 1).weight); 63             } else { 64                 w = Math.max(w, serverList.get(i + 1).weight); 65             } 66         } 67         return w; 68     } 69      70     /** 71      *  算法流程：  72      *  假设有一组服务器 S = {S0, S1, …, Sn-1} 73      *  有相应的权重，变量currentIndex表示上次选择的服务器 74      *  权值currentWeight初始化为0，currentIndex初始化为-1 ，当第一次的时候返回 权值取最大的那个服务器， 75      *  通过权重的不断递减 寻找 适合的服务器返回，直到轮询结束，权值返回为0  76      */ 77     public Server GetServer() { 78         while (true) { 79             currentIndex = (currentIndex + 1) % serverCount; 80             if (currentIndex == 0) { 81                 currentWeight = currentWeight - gcdWeight; 82                 if (currentWeight <= 0) { 83                     currentWeight = maxWeight; 84                     if (currentWeight == 0) 85                         return null; 86                 } 87             } 88             if (serverList.get(currentIndex).weight >= currentWeight) { 89                 return serverList.get(currentIndex); 90             } 91         } 92     } 93  94  95     class Server { 96         public String ip; 97         public int weight; 98         public Server(String ip, int weight) { 99             super();100             this.ip = ip;101             this.weight = weight;102         }103         public String getIp() {104             return ip;105         }106         public void setIp(String ip) {107             this.ip = ip;108         }109         public int getWeight() {110             return weight;111         }112         public void setWeight(int weight) {113             this.weight = weight;114         }115     }116     117 118     public void init() {119         Server s1 = new Server("192.168.0.100", 3);//3120         Server s2 = new Server("192.168.0.101", 2);//2121         Server s3 = new Server("192.168.0.102", 6);//6122         Server s4 = new Server("192.168.0.103", 4);//4123         Server s5 = new Server("192.168.0.104", 1);//1124         serverList = new ArrayList<Server>();125         serverList.add(s1);126         serverList.add(s2);127         serverList.add(s3);128         serverList.add(s4);129         serverList.add(s5);130         131         currentIndex = -1;132         currentWeight = 0;133         serverCount = serverList.size();134         maxWeight = getMaxWeightForServers(serverList);135         gcdWeight = getGCDForServers(serverList);136     }137     138     139     public static void main(String[] args) {140         WeightedRoundRobinScheduling obj = new WeightedRoundRobinScheduling();141         obj.init();142         143         Map<String,Integer> countResult = new HashMap<String,Integer>();144         145         for (int i = 0; i < 100; i++) {146             Server s = obj.GetServer();147             String log = "ip:"+s.ip+";weight:"+s.weight;148             if(countResult.containsKey(log)){149                 countResult.put(log,countResult.get(log)+1);150             }else{151                 countResult.put(log,1);152             }153             System.out.println(log);154         }155         156         for(Entry<String, Integer> map : countResult.entrySet()){157             System.out.println("服务器 "+map.getKey()+" 请求次数： "+map.getValue());158         }159     }160 161 }