做了一段时间的jdk８项目后，jdk９发布了，跟随时代的潮流，立马将jdk切换为９，然后。。。。。。　　运行什么的都没有问题，在进行mvn clean install后，吧啦吧啦的一大堆test error，单独运行一个子项目后发现，运行测试用例的时候程序抛异常了：

java.lang.IllegalStateException: Failed to load ApplicationContext at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83)at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:117)at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83)at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:44)at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:230)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:228)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:247)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)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$2.evaluate(ParentRunner.java:268)at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)at com.intellij.rt.execution.junit.IdeaTestRunner$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 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException`at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1078)at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:857)at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693)at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360)at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:120)at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)... 25 more`Caused by: java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException`at org.hibernate.boot.spi.XmlMappingBinderAccess.(XmlMappingBinderAccess.java:43)at org.hibernate.boot.MetadataSources.(MetadataSources.java:87)at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.(EntityManagerFactoryBuilderImpl.java:179)at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.(EntityManagerFactoryBuilderImpl.java:149)at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:54)at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353)at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:370)at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:359)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624)... 40 more`Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException`at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:185)at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)... 50 more

      直接绕过百度、必应，在ｇｏｏｇｌｅ上一搜，情况立马知晓了。ｓｔａｃｋｏｖｅｒｆｌｏｗ上面这么解释： The JAXB APIs are considered to be Java EE APIs, and therefore are no longer contained on the default class path in Java SE 9.Java 9 introduces the concepts of modules, and by default the `java.se` aggregate module is available on the class path (or rather, module path). 

As the name implies, the `java.se` aggregate module does _not_ include the Java EE APIs that have been traditionally bundled with Java 6/7/8.Fortunately, these Java EE APIs that were provided in JDK 6/7/8 are still in the JDK, but they just aren't on the class path by default. The extra Java EE APIs are provided in the following modules:```java.activationjava.corbajava.transactionjava.xml.bind << This one contains the JAXB APIsjava.xml.wsjava.xml.ws.annotation```

**Quick Solution:**To make the JAXB APIs available at runtime, specify the following command-line option:`--add-modules java.xml.bind`**But I still need this to work with Java 8!!!**

If you try specifying `--add-modules` with an older JDK, it will blow up becuase it's an unrecognized option. I suggest one of two options:

1. You can conditionally apply the argument in a launch script (if you have one) by inspecting the JDK version by inspecting `$JAVA_HOME/release` for the `JAVA_VERSION` property.

2. You can add the `-XX:+IgnoreUnrecognizedVMOptions` to make the JVM silently ignore unrecongized options, instead of blowing up. But beware! Any other command line args you use will no longer be validated for you by the JVM. This option works with Oracle/OpenJDK as well as IBM JDK (as of JDK 8sr4) 

       怎么样？看出来什么了么？简单来说，就是ｊｄｋ９的模块化功能造成的，`java.xml.bind`其实是属于ｊａｖａ　ｅｅ的模块，在ｊｄｋ６／７／８版本中都放在了默认的ｐａｔｈ下面，但是到了ｊｄｋ９，就把这些模块都移出来了，就是没有放在默认的ｐａｔｈ下面，如果想要使用，那么你需要在运行时加上ｏｐｔｉｏｎｓ命令`--add-modules java.xml.bind`。

 那么坑又来了，我一开始的时候以为是需要通过命令 `java --add-modules java.xml.bind`去添加模块，ｊａｖａ命令中也有这个命令，但就是提示命令可能有误，一直没反应。然后就去把ｇｏｏｇｌｅ各种翻，最终，结果找到了：

```Test FailureThe next step sees the failure of unit tests to fail with `mvn test`.The cause is the same, but it’s a bit harder to find. It requires checking the Surefire reports.

 Some contain exceptions with the following line:Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBExceptionAgain, test code cannot access the module. This time, however, the _maven-surefire-plugin_ needs to be configured:

<plugin>

<artifactId>maven-surefire-plugin</artifactId>

<version>2.20.1</version>

<configuration>

<argLine>--add-modules java.xml.bind</argLine>

</configuration>

 </plugin>

ok,在ｐｏｍ文件里面的插件配置里面加上这句话，加一个配置就搞定了。另外，在这个网站中也说明了，在编译、mvn　spring-boot:run、打包时出现这类异常该怎么解决，网址

`https://dzone.com/articles/migrating-a-spring-boot-application-to-java-9-comp(可能需要翻墙)`