<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>31.0.1-jre</version>
</dependency>

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class GuavaCacheExample {
    public static void main(String[] args) throws ExecutionException {
        // 創(chuàng)建一個LoadingCache實例
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100) // 設(shè)置緩存的最大容量
                .expireAfterWrite(10, TimeUnit.MINUTES) // 設(shè)置過期時間為10分鐘
                .build(new CacheLoader<String, String>() { // 定義默認的數(shù)據(jù)加載機制
                    @Override
                    public String load(String key) throws Exception {
                        return "value-" + key;
                    }
                });

        // 訪問緩存
        String value = cache.get("key1");
        System.out.println(value); // 輸出: value-key1
    }
}

try {
    String value = cache.get("key2");
} catch (ExecutionException e) {
    // 處理異常
    System.err.println("Failed to load value for key2: " + e.getCause());
}

// 手動加載
cache.put("key3", "value3");

// 手動刪除
cache.invalidate("key3");

CacheBuilder.newBuilder()
    .softValues() // 使用軟引用
    .weakKeys() // 使用弱引用
    .build();

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>31.0.1-jre</version>
</dependency>

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class UserCacheService {

    // 創(chuàng)建一個 Guava Cache 實例
    private final Cache<String, User> userCache;

    public UserCacheService() {
        // 配置緩存
        this.userCache = CacheBuilder.newBuilder()
                .maximumSize(1000) // 最大緩存條目數(shù)
                .expireAfterWrite(10, TimeUnit.MINUTES) // 緩存條目在寫入后 10 分鐘過期
                .recordStats() // 記錄緩存統(tǒng)計信息
                .build();
    }

    // 獲取用戶信息
    public User getUser(String userId) {
        try {
            return userCache.get(userId, () -> loadUserFromDatabase(userId));
        } catch (ExecutionException e) {
            throw new RuntimeException("Failed to load user from cache", e);
        }
    }

    // 從數(shù)據(jù)庫加載用戶信息
    private User loadUserFromDatabase(String userId) {
        // 模擬從數(shù)據(jù)庫加載用戶信息
        System.out.println("Loading user " + userId + " from database");
        return new User(userId, "User Name " + userId);
    }

    public static void main(String[] args) {
        UserCacheService service = new UserCacheService();

        // 模擬高并發(fā)請求
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                User user = service.getUser("12345");
                System.out.println("User: " + user);
            }).start();
        }
    }
}

class User {
    private String id;
    private String name;

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

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

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import java.util.concurrent.TimeUnit;

public class GuavaCacheExample {
    public static void main(String[] args) {
        // 創(chuàng)建一個最大容量為100，超過容量后使用LRU算法移除最近最少使用的條目，
        // 并且設(shè)置10分鐘后過期的緩存
        Cache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100)
                .expireAfterWrite(10, TimeUnit.MINUTES)
                .removalListener(notification -> System.out.println("Removed: " + notification.getKey()))
                .build();

        // 向緩存中添加數(shù)據(jù)
        cache.put("key1", "value1");

        // 從緩存中獲取數(shù)據(jù)
        String value = cache.getIfPresent("key1");
        System.out.println(value); // 輸出: value1
    }
}

import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class LoadingCacheExample {
    public static void main(String[] args) throws ExecutionException {
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100)
                .expireAfterWrite(10, TimeUnit.MINUTES)
                .build(new CacheLoader<String, String>() {
                    @Override
                    public String load(String key) throws Exception {
                        return fetchFromDatabase(key);
                    }
                });

        // 獲取數(shù)據(jù)，如果緩存中沒有，會自動調(diào)用load方法加載
        String value = cache.get("key1");
        System.out.println(value); // 輸出: 從數(shù)據(jù)庫獲取的數(shù)據(jù)
    }

    private static String fetchFromDatabase(String key) {
        // 模擬從數(shù)據(jù)庫查詢
        return "從數(shù)據(jù)庫獲取的數(shù)據(jù)";
    }
}