如何在Google App Engine中创建javax.el.E​​xpressionFactory以使用Hibernate Validator [英] How to create javax.el.ExpressionFactory in Google App Engine to use Hibernate Validator

问题描述

我正在尝试在我的Google App Engine应用程序上升级到休眠验证器版本6，该版本

I'm trying to upgrade to hibernate validator version 6 on my Google App Engine app, which needs javax.el, so I added org.glassfish:javax.el:jar:3.0.1-b10 to my dependencies.

但是，这是不使用的:

在本地开发环境中，我可以使用ExpressionFactory.newInstance()创建一个新的ExpressionFactory. ExpressionFactory来自本地Jetty安装jetty93/jetty-distribution/lib/apache-jsp/org.mortbay.jasper.apache-el-8.0.33.jar，它从同一jar返回实现org.apache.el.ExpressionFactoryImpl.

In the local dev environment, I can create a new ExpressionFactory with ExpressionFactory.newInstance(). The ExpressionFactory is from the local Jetty installation jetty93/jetty-distribution/lib/apache-jsp/org.mortbay.jasper.apache-el-8.0.33.jar and it returns the implementation org.apache.el.ExpressionFactoryImpl from the same jar.

在已部署的GAE环境中，ExpressionFactory来自java8_runtime/runtime-shared.jar!/javax/el/ExpressionFactory.class，但是ExpressionFactory.newInstance()仍然尝试获取org.apache.el.ExpressionFactoryImpl，即使存在com.sun.el.ExpressionFactoryImpl.

In the deployed GAE environment, the ExpressionFactory is from java8_runtime/runtime-shared.jar!/javax/el/ExpressionFactory.class but ExpressionFactory.newInstance() still tries to get a org.apache.el.ExpressionFactoryImpl, even though com.sun.el.ExpressionFactoryImpl is present.

在两种环境中，我都可以从WEB-INF/lib/javax.el-3.0.1-b10.jar手动加载com.sun.el.ExpressionFactoryImpl，因此它出现在类路径中:

In both environments, I can manually load a com.sun.el.ExpressionFactoryImpl from WEB-INF/lib/javax.el-3.0.1-b10.jar, so it is present in the classpath:

final Constructor<ExpressionFactoryImpl> constructor = com.sun.el.ExpressionFactoryImpl.class.getConstructor();
final ExpressionFactoryImpl expressionFactory = constructor.newInstance();

• 即使参考实现com.sun.el.ExpressionFactoryImpl位于类路径上，为什么GAE环境仍如此热衷于加载org.apache.el.ExpressionFactoryImpl?
• 如何使GAE加载现有的ExpressionFactoryImpl，以便创建休眠的ValidatorFactory?我是否必须手动提供
  • Why is the GAE environment so keen on loading org.apache.el.ExpressionFactoryImpl even though the reference implementation com.sun.el.ExpressionFactoryImpl is on the classpath?
  • How can I make GAE load the existing ExpressionFactoryImpl so I can create a hibernate ValidatorFactory? Do I have to manually supply a MessageInterpolator so I can supply the correct ExpressionFactoryImpl?

  推荐答案

  我终于通过在appengine-web.xml中添加系统属性来解决了这个问题:

  I finally solved it by adding a system property to appengine-web.xml:

  <system-properties>
      <property name="javax.el.ExpressionFactory" value="com.sun.el.ExpressionFactoryImpl" />
  </system-properties>
  

  另一种可能性是添加文件"META-INF/services/javax.el.E​​xpressionFactory"，内容如下:

  An other possibility could be to add the file 'META-INF/services/javax.el.ExpressionFactory' with the contents:

  com.sun.el.ExpressionFactoryImpl
  

  另请参见此答案

  我没有测试第二种方法，但是它在apache-el ExpressionFactory的源代码中具有最高的优先级，而系统属性只是第三种尝试.

  I didn't test the second method, but it has the highest priority in the source of apache-el ExpressionFactory, while the system property is only the third try.

  这篇关于如何在Google App Engine中创建javax.el.E​​xpressionFactory以使用Hibernate Validator的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！