java代码如何用缓存提升性能 java代码缓存应用的基础教程​

HashMap

import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;

import java.util.concurrent.TimeUnit;

public class UserCache {

    private final Cache<String, User> userCache;

    public UserCache() {
        userCache = Caffeine.newBuilder()
                .maximumSize(1000) // 缓存最大容量
                .expireAfterWrite(10, TimeUnit.MINUTES) // 写入后10分钟过期
                .build();
    }

    public User getUser(String userId) {
        // 从缓存中获取，如果不存在，则调用loadUser方法加载
        return userCache.get(userId, this::loadUser);
    }

    private User loadUser(String userId) {
        // 模拟从数据库加载用户
        System.out.println("Loading user from database: " + userId);
        // 这里应该是实际的数据库查询逻辑
        return new User(userId, "User " + userId);
    }

    public static void main(String[] args) {
        UserCache userCache = new UserCache();
        System.out.println(userCache.getUser("123"));
        System.out.println(userCache.getUser("123")); // 第二次直接从缓存获取
    }

    static class User {
        String id;
        String name;

        public User(String id, String name) {
            this.id = id;
            this.name = name;
        }

        @Override
        public String toString() {
            return "User{" +
                    "id='" + id + '\'' +
                    ", name='" + name + '\'' +
                    '}';
        }
    }
}

maximumSize

expireAfterWrite

userCache.get(userId, this::loadUser)

loadUser