问名为“play”的EhCache实例已经存在
EN

Stack Overflow用户

提问于 2017-04-05 15:34:50

回答 6查看 3.1K关注 0票数 2

我在使用异步 couchdatabase java驱动程序时，遇到了Play framework默认缓存(EHCache)的问题。在热重新加载时播放崩溃，错误如下：

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

我发现这可能不仅适用于couchdatabase驱动程序，而且也适用于其他一些场景，比如EUOCrov7M。

playframework

couchbase

ehcache

playframework-2.5

playframework-2.6

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回答 6

Stack Overflow用户

发布于 2017-04-05 15:34:50

我想出了一个解决方案-强制停止钩上的高速缓存关闭。它可以在项目中的一个现有模块中完成，例如：

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

还可以创建特殊的“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

票数 4

Stack Overflow用户

发布于 2017-07-27 06:49:51

如果有些人看了一下快速的复制修复，这里是我从Andriy的答案翻译出来的scala版本。

package utils

import javax.inject.{Inject, Singleton}

import com.google.inject.AbstractModule
import net.sf.ehcache.CacheManager
import play.api.Logger
import play.api.inject.ApplicationLifecycle

import scala.concurrent.{ExecutionContext, Future}

/**
  * Fix for the hot reloading cache issue.
  * "Error in custom provider, play.api.cache.EhCacheExistsException: An EhCache instance with name 'play' already exists."
  *
  */
class CacheHotReloadFix extends AbstractModule {
  override protected def configure(): Unit = {
    bind(classOf[CacheHotReloadFixInstance]).asEagerSingleton()
  }
}

@Singleton
class CacheHotReloadFixInstance @Inject() (lifecycle: ApplicationLifecycle, implicit val executionContext: ExecutionContext) {

  private val logger = Logger(this.getClass)

  lifecycle.addStopHook { () =>
    logger.debug("Forching ehcach to stop before play reloads")
    // Force cache to stop.
    Future(CacheManager.getInstance().shutdown())
  }
}

票数 1

Stack Overflow用户

发布于 2018-01-05 12:08:44

如果在运行测试用例时遇到问题(其中将有多个Applicaiton)，则可以使用SyncCacheApi和AsyncCacheApi的虚拟实现，并在通过provideApplication()创建Application时覆盖绑定。

    @Override
    protected Application provideApplication() {
Application application = new GuiceApplicationBuilder().configure(testConfig)
                        .disable(EhCacheModule.class)
    .overrides(bind(SyncCacheApi.class).to(FakeSyncCacheApi.class))
                        .bindings(new MyModule())
                        .in(new File(".")).build();
     return application;
}

而样本FakeSyncCacheApi应该类似于

@Singleton
public class FakeSyncCacheApi implements SyncCacheApi {

    private LRUMap cache = new LRUMap();

    @Override
    public <T> T get(String key) {
        return (T) cache.get(key);
    }

    @Override
    public <T> T getOrElseUpdate(String key, Callable<T> block, int expiration) {
        return getOrElseUpdate(key, block);
    }

    @Override
    public <T> T getOrElseUpdate(String key, Callable<T> block) {
        T value = (T) cache.get(key);
        if (value == null) {
            try {
                value = block.call();
            } catch (Exception e) {

            }
            cache.put(key, value);
        }
        return value;
    }

    @Override
    public void set(String key, Object value, int expiration) {
        cache.put(key, value);
    }

    @Override
    public void set(String key, Object value) {
        cache.put(key, value);
    }

    @Override
    public void remove(String key) {
        cache.remove(key);
    }
}