ThreadLocal的使用

最新推荐文章于 2023-03-02 11:02:32 发布

Sanyhem

最新推荐文章于 2023-03-02 11:02:32 发布

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本文链接：https://blog.youkuaiyun.com/IT_PL/article/details/103524364

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本文介绍了一个使用ThreadLocal实现的本地缓存解决方案。通过在ThreadLocal中存储用户数据，避免了多次数据库查询，提高了应用程序的性能。文章详细展示了如何在多线程环境中利用ThreadLocal进行数据隔离，以及如何在需要时从缓存中获取或更新数据。

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实现本地缓存

参考链接

@Slf4j
public class ThreadLocalCacheTest {

    private static final ThreadLocal<Map<Integer, User>> USER_THREAD_LOCAL = ThreadLocal.withInitial(HashMap::new);
    
    @Test
    public void test(){
        try{
            List<Integer> userIdList = Arrays.asList(1, 2, 3, 4, 3, 2);
            for (Integer userId : userIdList) {
                User userById = getUserById(userId);
                log.info(JSON.toJSONString(userById));
            }
        }finally {
            USER_THREAD_LOCAL .remove();
        }
    }

    /**
     *
     * @param id
     * @return
     */
    private User getUserById(Integer id){
        User user = USER_THREAD_LOCAL .get().get(id);
        if (Objects.nonNull(user)){
            log.info("从本地缓存中获取, id:[{}], user:[{}]", id, JSON.toJSONString(user));
            return user;
        }
        user = testData(id);
        USER_THREAD_LOCAL .get().put(id, user);
        return user;
    }

    /**
     * 模拟数据
     * @param id
     * @return
     */
    private User testData(Integer id) {
        List<User> list = Lists.newArrayList();
        list.add(new User(1, "username1", "13000000001", "address1" ));
        list.add(new User(2, "username2", "13000000002", "address2" ));
        list.add(new User(3, "username3", "13000000003", "address3" ));
        list.add(new User(4, "username4", "13000000004", "address4" ));

        Map<Integer, User> collect = list.stream().collect(Collectors.toMap(User::getId, Function.identity()));
        return collect.get(id);
    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User{
    private Integer id;
    private String username;
    private String moblie;
    private String address;
}