playframework - 名称为 'play' 的 EhCache 实例已存在

Question

在使用异步 couchdatabase java 驱动程序时，我遇到了 Play 框架 默认缓存 (EHCache) 的问题。热重载时 Play 崩溃并出现错误:

Error in custom provider, play.api.cache.EhCacheExistsException: An EhCache instance with name 'play' already exists.

我发现这不仅可能与couchdatabase驱动程序有关，而且在其他一些场景中也可能发生，例如https://groups.google.com/forum/#!topic/pac4j-dev/2_EUOCrov7M .

Answer 1

我找到了一个解决方案 - 在停止钩子(Hook)上强制关闭缓存。它可以在项目中的现有模块之一中完成，例如:

lifecycle.addStopHook(() -> {
  ...
  CacheManager.getInstance().shutdown();
  ...
});

也可以创建特殊的“修复”模块:

package fixes;

import java.util.concurrent.CompletableFuture;

import javax.inject.Inject;
import javax.inject.Singleton;

import com.google.inject.AbstractModule;

import net.sf.ehcache.CacheManager;
import play.Logger;
import play.Logger.ALogger;
import play.inject.ApplicationLifecycle;

/**
 * Fix for the hot reloading cache issue.
 * "Error in custom provider, play.api.cache.EhCacheExistsException: An EhCache instance with name 'play' already exists."
 *
 */
public class CacheFix  extends AbstractModule{  
    @Override
    protected void configure() {
        bind(CacheFixInstance.class).asEagerSingleton();        
    }
}


/**
 * Only stop hook
 */
@Singleton
class CacheFixInstance {    
    private static ALogger logger = Logger.of(CacheFixInstance.class);

    @Inject
    public CacheFixInstance(ApplicationLifecycle lifecycle) {
        lifecycle.addStopHook(() -> {

            // Force cache to stop.
            CacheManager.getInstance().shutdown();
            logger.debug("Cache has been shutdown");

            // Nothing to return.
            return CompletableFuture.completedFuture(null);
        });
    }
}

在application.conf中:

enabled += fixes.CacheFix