java项目构建从高版本JDK改为低版本JDK报错。这是再次编译时使用的JDK版本比你原来编译的版本低所导致的。maven项目在服务器上构建时报错（Unsupported major.minor version 52.0 ）：
java.lang.UnsupportedClassVersionError: com/byron4j/listener/InitListener : Unsupported major.minor version 52.0 (unable to load class com.byron4j.listener.InitListener)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2961)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1210)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1690)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:506)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:488)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:115)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4932)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5528)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1095)
at org.apache.catalina.startup.HostConfigDeployWar.run(HostConfig.java:1930)atjava.util.concurrent.ExecutorsRunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
部署到linux服务器上之后，启动项目时报Unsupported major.minor version 52.0 错误，检查发现是linux服务器上JDK版本过低导致的，然后将项目指定JDK版本为1.7，再发布启动OK了。
JDK版本在官方对应的版本号列表如下：
JDK 8.0 = 52,
JDK 7.0 = 51,
JDK 6.0 = 50,
JDK 5.0 = 49,
JDK 1.4 = 48,
JDK 1.3 = 47,
JDK 1.2 = 46,
JDK 1.1 = 45
正是指定的JDK版本为52，但是由于服务器是JDK 7导致引发Unsupported major.minor version 52.0