问题一：
java.lang.UnsupportedClassVersionError: org/apache/catalina/startup/Bootstrap : (Unsupported major.minor version 55.0)
原因是因为jdk版本太低了，tomcat8支持，更换更高级的jdk或者使用低版本的tomcat。
这里我将jdk换成jdk1.8：
但重启tomcat8后，有出现如下错误：
tomcat7Server [Remote Java Application] org.apache.catalina.startup.Bootstrap at localhost:59723 Thread [main] (Suspended (exception UnsupportedClassVersionError)) Launcher$AppClassLoader(ClassLoader).defineTransformedClass(String, byte[], int, int, ProtectionDomain, ClassFormatError, String) line: 529 Launcher$AppClassLoader(ClassLoader).defineClass(String, byte[], int, int, ProtectionDomain) line: 623 Launcher$AppClassLoader(SecureClassLoader).defineClass(String, byte[], int, int, CodeSource) line: 124 Launcher$AppClassLoader(URLClassLoader).defineClass(String, Resource) line: 260 URLClassLoader.access$000(URLClassLoader, String, Resource) line: 56 URLClassLoader$1.run() line: 195 AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$AppClassLoader(URLClassLoader).findClass(String) line: 188 Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: 307 Launcher$AppClassLoader.loadClass(String, boolean) line: 301 Launcher$AppClassLoader(ClassLoader).loadClass(String) line: 252 Launcher$AppClassLoader(ClassLoader).loadClassInternal(String) line: 320 d:\MyEclipse\Common\binary\com.sun.java.jdk.win32.x86_64_1.6.0.013\bin\javaw.exe (2014-5-8 下午9:01:59)
原因是tomcat配置的jdk与myeclipse中的不一致。
现在将其换成jdk1.8即可。