springboot项目启动抛: java.lang.NoClassDefFoundError: javax/el/ELManager

借助外部tomcat7， 启动springboot（2.0.5.RELEASE）项目，抛出错误

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.validation.beanvalidation.LocalValidatorFactoryBean]: Factory method 'defaultValidator' threw exception; nested exception is java.lang.NoClassDefFoundError: javax/el/ELManager
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:582)
	... 63 more
Caused by: java.lang.NoClassDefFoundError: javax/el/ELManager
	at org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.buildExpressionFactory(ResourceBundleMessageInterpolator.java:88)
	at org.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.(ResourceBundleMessageInterpolator.java:47)
	at org.hibernate.validator.internal.engine.ConfigurationImpl.getDefaultMessageInterpolator(ConfigurationImpl.java:474)
	at org.springframework.boot.validation.MessageInterpolatorFactory.getObject(MessageInterpolatorFactory.java:54)
	at org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration.defaultValidator(ValidationAutoConfiguration.java:57)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	... 64 more

查看具体原因，发现缺少ELManager这个类。这个类在javax.el-api中，添加pom依赖还是失败。有博友说将tomcat 7中的这个jar拷贝到jdk中，但是仍不起作用。

耐心排查了一下，是因为当前版本的springboot，依赖的验证hibernate-validator版本太高，导致找不到ELManager。终极解决办法，直接管理hibernate-validator，顺利解决。

    org.hibernate.validator
    hibernate-validator
    5.1.1.Final