Guava缓存使用

public class GuavaCache {


    /**
     * LoadingCache当缓冲中不存在时,可自动加载
     * */
    private static LoadingCache<Integer,Student> studentCache = CacheBuilder.newBuilder()
                                                                     /**
                                                                      * 设置写入缓存后过期时间(8秒过期)
                                                                      * */
                                                                     .expireAfterWrite(8, TimeUnit.SECONDS)
                                                                     /**
                                                                      * 使用SoftReference封装value,当内存不足时,自动回收
                                                                      * */
                                                                     .softValues()
                                                                     /**
                                                                      * 设置缓存初始化容量
                                                                      * */
                                                                     .initialCapacity(100)
                                                                     /**
                                                                      * 设置缓存对象权重
                                                                      * */
                                                                     .weigher(new Weigher<Integer, Student>() {
                                                                         @Override
                                                                         public int weigh(Integer key, Student value) {
                                                                             return key % 2 == 0 ? 1 : 0;
                                                                         }
                                                                     })
                                                                     /**
                                                                      * 统计缓存命中率
                                                                      * */
                                                                     .recordStats()
                                                                     /**
                                                                      * 定义缓存对象失效的时间精度位纳秒级
                                                                      * */
                                                                     .ticker(Ticker.systemTicker())
                                                                     /**
                                                                      * 设置缓存移除通知
                                                                      * */
                                                                     .removalListener(new RemovalListener<Object, Object>() {
                                                                         @Override
                                                                         public void onRemoval(RemovalNotification<Object, Object> notification) {
                                                                             System.out.println((Integer) notification.getKey() + " was removed , " +
                                                                                     "cause is " + notification.getCause());
                                                                         }
                                                                     })
                                                                     /**
                                                                      * build方法指定CacheLoader,实现数据自动加载
                                                                      * */
                                                                     .build(new CacheLoader<Integer, Student>() {
                                                                         @Override
                                                                         public Student load(Integer key) throws Exception {
                                                                             Student st = new Student();
                                                                             st.setStudentNo(key);
                                                                             return st;
                                                                         }
                                                                     });

    /**
     * Cache.get(key, Callable)
     * 当缓存中不存在key对应缓存对象时,调用Callable获取
     * */
    public static final Student getStudent(Integer key) throws ExecutionException {
        try {
            return studentCache.get(key, new Callable<Student>() {
                @Override
                public Student call() throws Exception {
                    Student st = new Student();
                    st.setStudentNo(key);
                    return st;
                }
            });
        } finally {
            System.out.println("Cache hit stats : " + studentCache.stats().toString());
        }
    }

    public static final void testStudentCache() throws ExecutionException, InterruptedException {
        for (int i = 0; i < 20; ++i) {
            Student student = studentCache.get(i);
            System.out.println(student);
            TimeUnit.SECONDS.sleep(1);
        }
        System.out.println("Cache hit stats : " + studentCache.stats().toString());
    }

    public static final void testConcurrentStudentCache(int threadNumber) throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(100);
        Random random = new Random();
        ExecutorService es = Executors.newFixedThreadPool(threadNumber);
        for (int i = 0; i < 200; ++i) {
            es.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        studentCache.get(random.nextInt(20));
                        TimeUnit.SECONDS.sleep(1);
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        latch.countDown();
                    }
                }
            });
        }
        latch.await();
        es.shutdown();
        System.out.println("Cache hit stats : " + studentCache.stats().toString());
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
//        GuavaCache.testStudentCache();

        GuavaCache.getStudent(1);
        GuavaCache.getStudent(1);
    }
}