Diamond types are not supported at this language level解决
project的java level 已经核实确实为8，但是IDEA里面仍然会有如下图的提示:
通过查看项目设置，发现project的java level 也是8。
然后继续检查其他模块 如modules ，发现了问题所在。
改为8就好了。
遇到类似问题重点排查的位置：
project structure中的project，module中的sources和setting中的java compiler
Error:java: Compilation failed: internal java compiler error解决
在修改完上面的问题后出现了这个问题：Error:java: Compilation failed: internal java compiler error
把这里改成相应的版本就可以了。
一般改完以上的两个，项目就可以正常运行了，我这里又出现了jdk的版本的问题，这里顺便解决一下：
ASM ClassReader failed to parse class file的问题解决
Caused by: org.springframework.beans.factory.BeanDefinitionStoreException: Failed to read candidate component class: file [D:\NewWorkSpace\ep-user\target\test-classes\org\homework\ep\user\base\BaseTest.class]; nested exception is org.springframework.core.NestedIOException: ASM ClassReader failed to parse class file - probably due to a new Java class file version that isn't supported yet: file [D:\NewWorkSpace\ep-user\target\test-classes\org\homework\ep\user\base\BaseTest.class]; nested exception is java.lang.IllegalArgumentException
at org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.findCandidateComponents(ClassPathScanningCandidateComponentProvider.java:290)
at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.doScan(ClassPathBeanDefinitionScanner.java:242)
at org.springframework.context.annotation.ComponentScanBeanDefinitionParser.parse(ComponentScanBeanDefinitionParser.java:84)
at org.springframework.beans.factory.xml.NamespaceHandlerSupport.parse(NamespaceHandlerSupport.java:73)
at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1438)
at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1428)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:185)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:139)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:108)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:493)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:390)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:334)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:302)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:174)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:209)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:243)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadBeanDefinitions(AbstractGenericContextLoader.java:233)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:117)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:100)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:248)
at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContextInternal(CacheAwareContextLoaderDelegate.java:64)
at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContext(CacheAwareContextLoaderDelegate.java:91)
... 25 more
Caused by: org.springframework.core.NestedIOException: ASM ClassReader failed to parse class file - probably due to a new Java class file version that isn't supported yet: file [D:\NewWorkSpace\ep-user\target\test-classes\org\homework\ep\user\base\BaseTest.class]; nested exception is java.lang.IllegalArgumentException
at org.springframework.core.type.classreading.SimpleMetadataReader.<init>(SimpleMetadataReader.java:56)
at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:80)
at org.springframework.core.type.classreading.CachingMetadataReaderFactory.getMetadataReader(CachingMetadataReaderFactory.java:102)
at org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.findCandidateComponents(ClassPathScanningCandidateComponentProvider.java:266)
... 48 more
Caused by: java.lang.IllegalArgumentException
at org.springframework.asm.ClassReader.<init>(Unknown Source)
at org.springframework.asm.ClassReader.<init>(Unknown Source)
at org.springframework.asm.ClassReader.<init>(Unknown Source)
at org.springframework.core.type.classreading.SimpleMetadataReader.<init>(SimpleMetadataReader.java:53)
... 51 more
“ASM ClassReader failed to parse class file”是其中主要的原因。检查Maven的类库，没有发现问题，无asm显性依赖，其依赖产生于spring本身。故分析有可能是spring本身的问题造成了；但是这么流行的spring，怎么会出错了，我不能这么牛x碰到这么简单的问题吧？
难道是版本？除了版本之外，spring无大区别。经过一般搜索，网上还真有类似的问题：
Note that the Java 8 bytecode level (-target 1.8, as required by -source 1.8) is only fully supported as of Spring Framework 4.0.
In particular, Spring 3.2 based applications need to be compiled with a maximum of Java 7 as the target,
even if they happen to be deployed onto a Java 8 runtime. Please upgrade to Spring 4 for Java 8 based applications.
所以，看明白了吧，方案有两条：
a. 使用jdk7
b. 升级spring 4
4. 问题解决
最终选择了使用jdk7，因为项目的一些问题，所以选择这个，升级spring也是能解决的。