java - Spring :为什么在单元测试中加载应用程序上下文时需要添加javax.el-api依赖项？

我使用spring-mvc创建了一个简单的Spring 5应用程序。在我的一个模型对象中，我使用了bean验证(hibernate-validator)。我添加了以下配置以使其全部正常工作:

@Configuration
@ComponentScan(basePackages = "nl.myprod.springcrud")
public class AppConfig {

    @Bean
    public MethodValidationPostProcessor methodValidationPostProcessor() {
        return new MethodValidationPostProcessor();
    }

}

使用Gretty启动我的完整应用程序时，一切都会按预期进行。但是当我运行以下测试时...

@RunWith(SpringRunner.class)
@WebAppConfiguration
@ContextConfiguration(classes = {WebConfig.class})
public class tmpTest {

    @Test
    public void tmp () {

    }

}

...它为我提供了以下堆栈跟踪:

java.lang.IllegalStateException: Failed to load ApplicationContext
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:125)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:108)
    at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:190)
    at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:132)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:246)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'methodValidationPostProcessor' defined in class path resource [nl/myprod/springcrud/config/AppConfig.class]: Invocation of init method failed; nested exception is javax.validation.ValidationException: HV000183: Unable to initialize 'javax.el.ExpressionFactory'. Check that you have the EL dependencies on the classpath, or use ParameterMessageInterpolator instead
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1745)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:576)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:204)
    at org.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:228)
    at org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:707)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:531)
    at org.springframework.test.context.web.AbstractGenericWebContextLoader.loadContext(AbstractGenericWebContextLoader.java:129)
    at org.springframework.test.context.web.AbstractGenericWebContextLoader.loadContext(AbstractGenericWebContextLoader.java:61)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:275)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:243)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:117)
    ... 24 more
Caused by: javax.validation.ValidationException: HV000183: Unable to initialize 'javax.el.ExpressionFactory'. Check that you have the EL dependencies on the classpath, or use ParameterMessageInterpolator instead
    at org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.buildExpressionFactory(ResourceBundleMessageInterpolator.java:116)
    at org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.<init>(ResourceBundleMessageInterpolator.java:47)
    at org.hibernate.validator.internal.engine.ConfigurationImpl.getDefaultMessageInterpolator(ConfigurationImpl.java:474)
    at org.hibernate.validator.internal.engine.ConfigurationImpl.getDefaultMessageInterpolatorConfiguredWithClassLoader(ConfigurationImpl.java:650)
    at org.hibernate.validator.internal.engine.ConfigurationImpl.getMessageInterpolator(ConfigurationImpl.java:397)
    at org.hibernate.validator.internal.engine.ValidatorFactoryImpl.<init>(ValidatorFactoryImpl.java:183)
    at org.hibernate.validator.HibernateValidator.buildValidatorFactory(HibernateValidator.java:38)
    at org.hibernate.validator.internal.engine.ConfigurationImpl.buildValidatorFactory(ConfigurationImpl.java:364)
    at javax.validation.Validation.buildDefaultValidatorFactory(Validation.java:103)
    at org.springframework.validation.beanvalidation.MethodValidationInterceptor.<init>(MethodValidationInterceptor.java:68)
    at org.springframework.validation.beanvalidation.MethodValidationPostProcessor.createMethodValidationAdvice(MethodValidationPostProcessor.java:125)
    at org.springframework.validation.beanvalidation.MethodValidationPostProcessor.afterPropertiesSet(MethodValidationPostProcessor.java:113)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1804)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1741)
    ... 39 more
Caused by: java.lang.NoClassDefFoundError: javax/el/ELManager
    at org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.buildExpressionFactory(ResourceBundleMessageInterpolator.java:108)
    ... 52 more
Caused by: java.lang.ClassNotFoundException: javax.el.ELManager
    at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 53 more

现在，我知道可以通过在build.gradle中添加以下依赖项来解决此问题:
compile group: 'org.glassfish', name: 'javax.el', version: '3.0.0'
而且我也可以通过不加载我的ApplicationContext(在测试中将@ContextConfiguration(classes = {WebConfig.class})注释掉)来解决此问题。

但是我看不到为什么在使用Gretty时我的代码可以正常工作，但是在测试中配置失败。谁能向我解释为什么？

PS:这是我的build.gradle:

plugins {
    id 'java'
    id 'org.gretty' version '2.3.1'
}

gretty {
    httpPort=8081
}

group 'nl.myprod'
version '1.0-SNAPSHOT'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
    jcenter()
}

dependencies {
    compile group: 'org.springframework', name: 'spring-webmvc', version: '5.1.4.RELEASE'
    compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.7'

    testCompile group: 'junit', name: 'junit', version: '4.12'
    testCompile group: 'org.springframework', name: 'spring-test', version: '5.1.4.RELEASE'
    testCompile group: 'org.mockito', name: 'mockito-all', version: '1.10.19'
    testCompile group: 'org.hamcrest', name: 'hamcrest-all', version: '1.3'

    compile group: 'javax.validation', name: 'validation-api', version: '2.0.1.Final'
    compile group: 'org.hibernate.validator', name: 'hibernate-validator', version: '6.0.13.Final'
}

最佳答案

看起来，当您至少在Tomcat模式下启动Gretty时，它包括那些EL类的一些实现。

以下文件具有EL依赖性:

https://github.com/akhikhl/gretty/blob/master/libs/gretty-runner-tomcat8/build.gradle:compile "org.apache.tomcat.embed:tomcat-embed-el:$tomcat8_version"

https://github.com/akhikhl/gretty/blob/master/libs/gretty-runner-tomcat7/build.gradle:compile "org.apache.tomcat.embed:tomcat-embed-el:$tomcat7_version"