使用redisson 分布式锁 会导致 线程并行执行，在秒杀系统中导致并发下降，此时可以对库存进行分段 如 stockCount = 40 分成四十段，分段的段数和总库存 相关， 用户请求时，随机分配一个段，若获取失败再重试几次，以保证尽可能购买到，详细代码如下
book 不使用锁 本机测试 20000/分钟
bookWithLock：使用分布式锁 但是没有分段 测试结果 1000/分钟
bookWithLock2 使用分布式锁 分段20时测试结果12000/分钟 分段40时测试结果 16000/分钟

1. @Slf4j
2. @Service
3. public class OrderServiceImpl implements OrderService {
5. private static String key = "count";
6. private static int stockCount = 40;
8. @Autowired
9. private RedissonClient redissonClient;
11. @Autowired
12. private StringRedisTemplate stringRedisTemplate;
14. @Override
15. public String book() {
16. return this.decrementOrder();
17. }
20. @Override
21. public String bookWithLock() {
22. RLock lock = this.redissonClient.getLock("lock");
23. Boolean result = false;
24. try {
26. result = lock.tryLock(10, TimeUnit.SECONDS);
27. if (result) {
28. return this.decrementOrder();
29. } else {
30. log.info("==================获取锁失败================");
31. }
33. // Boolean result = lock.tryLock(10, TimeUnit.SECONDS);
34. // if (result) {
35. // return this.decrementOrder();
36. // } else {
37. // log.info("获取锁失败");
38. // return "获取锁失败";
39. // }
41. } catch (Exception e) {
42. log.error(e.getMessage());
43. return "预定失败";
44. } finally {
45. if (result) {
46. lock.unlock();
47. }
48. }
49. return "0";
50. }
53. private String decrementOrder() {
54. Long count = Long.valueOf(this.stringRedisTemplate.opsForValue().get(key));
55. if (count > 0) {
56. count = this.stringRedisTemplate.opsForValue().decrement(key);
57. log.info("==================库存还剩{}个================", count);
58. return String.valueOf(count);
59. } else {
60. log.info("库存不足");
61. }
62. return "库存不足";
63. }
66. @Override
67. public Long initCount(Long count) {
68. count = count == null ? 100000 : count;
69. if (count < stockCount) {
70. stockCount = 1;
71. this.stringRedisTemplate.opsForValue().set(key + "_0", count.toString());
72. } else {
73. for (int i = 0; i < stockCount; i++) {
74. this.stringRedisTemplate.opsForValue().set(key + "_" + i, String.valueOf(count / stockCount));
75. }
76. if (count % stockCount != 0) {
77. this.stringRedisTemplate.opsForValue().set(key + "_" + 0, String.valueOf(count / stockCount + count % stockCount));
78. }
79. }
80. this.stringRedisTemplate.opsForValue().set(key, count.toString());
81. return Long.valueOf(this.stringRedisTemplate.opsForValue().get(key));
82. }
84. @Override
85. public String bookWithLock2() {
87. RLock lock = null;
88. Boolean result = false;
89. //尝试三次
90. for (int i = 0; i < 3; i++) {
91. try {
92. int index = getRandom(stockCount);
93. lock = this.redissonClient.getLock("lock" + index);
94. result = lock.tryLock(10, TimeUnit.SECONDS);
95. if (result) {
96. String count = decrementOrder2(index);
97. //如果没获取到（某个段的库存不足）则释放锁
98. if ("-1".equals(count)) {
99. lock.unlock();
100. } else {
101. return count;
102. }
103. }
104. } catch (Exception ex) {
105. log.error("执行失败", ex);
106. } finally {
107. if (result && lock != null) {
108. try {
109. lock.unlock();
110. } catch (IllegalMonitorStateException e) {
111. }
112. }
113. }
115. }
116. log.info("预定失败");
118. return "0";
121. }
124. private String decrementOrder2(Integer index) {
125. index = index == null ? 0 : index;
126. //尝试获取次数
128. String keyTemp = key + "_" + index;
130. Long count = Long.valueOf(this.stringRedisTemplate.opsForValue().get(keyTemp));
131. if (count > 0) {
132. count = this.stringRedisTemplate.opsForValue().decrement(keyTemp);
133. log.info("==================库存还剩{}个================", count);
134. return String.valueOf(count);
135. }
137. log.info("获取是失败.......");
138. return "-1";
139. }
142. private int getRandom(int count) {
143. return new Random().nextInt(count);
144. }
147. }