為了提升專案的併發效能，考慮引入本地記憶體Cache，對：外部資料來源訪問、Restful API呼叫、可重用的複雜計算 等3種類型的函式處理結果進行快取。目前採用的是spring Cache的@Cacheable註解方式，快取具體實現選取的是Guava Cache。
具體快取的配置此處不再介紹，重點對於key的配置進行說明：

1、基本形式

@Cacheable(value="cacheName", key"#id")  
public ResultDTO method(int id); 

2、組合形式

@Cacheable(value="cacheName", key"T(String).valueOf(#name).concat('-').concat(#password))  
public ResultDTO method(int name, String password);  
 

3、物件形式

@Cacheable(value="cacheName", key"#user.id)
public ResultDTO method(User user);

4、自定義key生成器

@Cacheable(value="gomeo2oCache", keyGenerator = "keyGenerator")
public ResultDTO method(User user);

@Component
public class CacheTestImpl implements CacheTest {
    @Cacheable("databaseCache")
    public Long test1()
    { return 1L; }

    @Cacheable("databaseCache")
    public Long test2()
    { return 2L; }

    @Cacheable("databaseCache")
    public Long test3()
    { return 3L; }

    @Cacheable("databaseCache")
    public String test4()
    { return "4"; }
}
 

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ClassCastException: java.lang.Long cannot be cast to java.lang.String

class CacheKeyGenerator implements KeyGenerator {
    // custom cache key
    public static final int NO_PARAM_KEY = 0;
    public static final int NULL_PARAM_KEY = 53;
    
    @Override
    public Object generate(Object target, Method method, Object... params) {

        StringBuilder key = new StringBuilder();
        key.append(target.getClass().getSimpleName()).append(".").append(method.getName()).append(":");
        if (params.length == 0) {
            return key.append(NO_PARAM_KEY).toString();
        }
        for (Object param : params) {
            if (param == null) {
                log.warn("input null param for Spring cache, use default key={}", NULL_PARAM_KEY);
                key.append(NULL_PARAM_KEY);
            } else if (ClassUtils.isPrimitiveArray(param.getClass())) {
                int length = Array.getLength(param);
                for (int i = 0; i < length; i++) {
                    key.append(Array.get(param, i));
                    key.append(',');
                }
            } else if (ClassUtils.isPrimitiveOrWrapper(param.getClass()) || param instanceof String) {
                key.append(param);
            } else {
                log.warn("Using an object as a cache key may lead to unexpected results. " +
                        "Either use @Cacheable(key=..) or implement CacheKey. Method is " + target.getClass() + "#" + method.getName());
                key.append(param.hashCode());
            }
            key.append('-');
        }

        String finalKey = key.toString();
        long cacheKeyHash = Hashing.murmur3_128().hashString(finalKey, Charset.defaultCharset()).asLong();
        log.debug("using cache key={} hashCode={}", finalKey, cacheKeyHash);
        return key.toString();
    }
}