今天專案從jdk7升級到jdk8，Tomcat啟動竟然報出這個執行時錯誤。

錯誤資訊：java.io.IOException: invalid constant type: 18

2015-09-17 09:06:16:ERROR localhost-startStop-1 org.springframework.web.context.ContextLoader - Context initialization failed
java.lang.RuntimeException: java.io.IOException: invalid constant type: 18
	at javassist.CtClassType.getClassFile2(CtClassType.java:203)
	at javassist.CtClassType.subtypeOf(CtClassType.java:303)
	at javassist.CtClassType.subtypeOf(CtClassType.java:318)
	at javassist.compiler.MemberResolver.compareSignature(MemberResolver.java:247)
	at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:119)
	at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:96)
	at javassist.compiler.TypeChecker.atMethodCallCore(TypeChecker.java:704)
	at javassist.compiler.TypeChecker.atCallExpr(TypeChecker.java:681)
	at javassist.compiler.JvstTypeChecker.atCallExpr(JvstTypeChecker.java:156)
	at javassist.compiler.ast.CallExpr.accept(CallExpr.java:45)
	at javassist.compiler.JvstTypeChecker.atCastToWrapper(JvstTypeChecker.java:125)
	at javassist.compiler.JvstTypeChecker.atCastExpr(JvstTypeChecker.java:97)
	at javassist.compiler.ast.CastExpr.accept(CastExpr.java:54)
	at javassist.compiler.CodeGen.doTypeCheck(CodeGen.java:241)
	at javassist.compiler.CodeGen.compileExpr(CodeGen.java:228)
	at javassist.compiler.CodeGen.atReturnStmnt2(CodeGen.java:597)
	at javassist.compiler.JvstCodeGen.atReturnStmnt(JvstCodeGen.java:424)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:362)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:350)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.CodeGen.atIfStmnt(CodeGen.java:390)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:354)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:350)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.MemberCodeGen.atTryStmnt(MemberCodeGen.java:203)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:366)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:350)
	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
	at javassist.compiler.CodeGen.atMethodBody(CodeGen.java:291)
	at javassist.compiler.CodeGen.atMethodDecl(CodeGen.java:273)
	at javassist.compiler.ast.MethodDecl.accept(MethodDecl.java:43)
	at javassist.compiler.Javac.compileMethod(Javac.java:168)
	at javassist.compiler.Javac.compile(Javac.java:94)
	at javassist.CtNewMethod.make(CtNewMethod.java:73)
	at javassist.CtNewMethod.make(CtNewMethod.java:44)
	at com.alibaba.dubbo.common.bytecode.ClassGenerator.toClass(ClassGenerator.java:318)
	at com.alibaba.dubbo.common.bytecode.Wrapper.makeWrapper(Wrapper.java:346)
	at com.alibaba.dubbo.common.bytecode.Wrapper.getWrapper(Wrapper.java:89)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrlsFor1Protocol(ServiceConfig.java:426)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrls(ServiceConfig.java:281)
	at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:242)
	at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:143)
	at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:109)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:97)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:327)
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:941)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:475)
	at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:388)
	at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:293)
	at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111)
	at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5003)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5517)
	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.HostConfig$DeployWar.run(HostConfig.java:1930)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: invalid constant type: 18
	at javassist.bytecode.ConstPool.readOne(ConstPool.java:1090)
	at javassist.bytecode.ConstPool.read(ConstPool.java:1033)
	at javassist.bytecode.ConstPool.<init>(ConstPool.java:149)
	at javassist.bytecode.ClassFile.read(ClassFile.java:737)
	at javassist.bytecode.ClassFile.<init>(ClassFile.java:108)
	at javassist.CtClassType.getClassFile2(CtClassType.java:190)
	... 65 more
 

解決方法：

網上查了一下有人說是javassist3.18.1以下版本在jdk8版本下不工作，而我使用的版本是3.12.1，果斷更換到3.18.1版本後，啟動依然不行！
又有網友說asm5以下的版本在jdk8下也不工作，而另一個已經停止更新的類庫cglib，它的最新版本3.0最高只能支援到asm4，
所以最後的解決方法是：刪除 cglib, asm 升級到5.0.4, javassist 升級到 3.18.0 以上，測試成功！

相關類庫介紹：

ASM 是一個 Java 位元組碼操控框架。它能夠以二進位制形式修改已有類或者動態生成類。
ASM 可以直接產生二進位制 class 檔案，也可以在類被載入入 Java 虛擬機器之前動態改變類行為。
ASM 從類檔案中讀入資訊後，能夠改變類行為，分析類資訊，甚至能夠根據使用者要求生成新類。
CGlib（Code Generation Library）能夠在程式執行的時候動態生成介面的實現類和繼承於某個類的子類，它是依賴於ASM的。
Javassist是一個開源的分析、編輯和建立Java位元組碼的類庫，能動態改變類的結構，或者動態生成類。

目前CGlib已經停止更新，Javassist已經取代了CGlib的功能。