tomcat初始化類加載

1、Tomcat解析之初始化類加載器（截圖）全部 Hibernate Spring Struts iBATIS 企業(yè)應(yīng)用 Lucene SOAJava 綜合設(shè)計(jì) 模式 Tomcat OOJBoss?上一頁(yè)1 2下一頁(yè)？瀏覽7744次鎖定老帖子 主題：Tomcat解析之初始化類加載器（截圖）該帖已經(jīng)被評(píng)為精華帖作者正文發(fā)表時(shí)間：2010-01-30最后修改：2010-02-01國(guó)< > 獵頭職位：上海：【上?！客赓Y企業(yè)高新誠(chéng)聘 web開發(fā)工程 師囹相關(guān)文章：源代碼分析一一啟動(dòng)過程（二）« Tomcat源代碼分析之ClassLoader«How Tomcat Works

2、翻譯（7）之Tomcat類加載器續(xù)集 gogole_09推薦群組：Tapestry等更多相關(guān)推薦級(jí)：CHjava綜合*性之前有寫過關(guān)于tomcat中常用的一些類結(jié)構(gòu)的文章。別：樣 解析Tomcat之HttpServlet（ 截圖記錄）*文章：今天來關(guān)注一下，tomcat的類加載器相關(guān)的內(nèi)容。213積 PS:由于前一篇文章內(nèi)容比較簡(jiǎn)單，有朋友冠以我標(biāo)題黨之嫌，分：對(duì)于此種說法，本人深感抱歉，可能標(biāo)題確實(shí)有點(diǎn)大，但是這些常 420用的類，我更多的時(shí)候只關(guān)注其用法，而忽略了內(nèi)部實(shí)現(xiàn)，所以也來 就把這些內(nèi)容總結(jié)了一下，發(fā)了出來。別無(wú)標(biāo)題黨之意，請(qǐng)各位eyer 自：海涵。杭州OK，現(xiàn)在進(jìn)入正題.Tomc

3、at類加載器初始化.開始之前，我們首先需要了解一下幾個(gè)基本的知識(shí)點(diǎn)；1. tomcat中類加載器的結(jié)構(gòu)與關(guān)系。這里，我引用tomcat文檔的一個(gè)簡(jiǎn)圖來說明一下，有興趣深究的朋友，可以去翻看tomcat的文檔，理解更多信息.作者正文(tomcat5.5)(由于參考的是tomcat6.0的源代碼，這里糾正一下類加載器的 圖(如下)，以免給別的朋友造成誤解，同時(shí)也多謝asialee給出的提醒)BootstrapISystemICommon/ Webappl WebappZ * *(tomcat6.0)2. 每種類加載器分別加載什么資源：這些內(nèi)容，可以在tomcat文檔的 Class Loader H

4、OW-TO找到這里我要說明的是，在tomcat中，這些內(nèi)容是記錄在哪里的。既(程序怎么讓tomcat知道，需要加載哪些類)答案是-其通過一個(gè)配置文件來指定的：(catali perties),這個(gè)文件默認(rèn)存放在tomcat 路徑下的 bin/bootstrap.jar 中。如圖打開文件，其內(nèi)容如下：Java代碼門1. # Licensed to the Apache Software Foundation(ASF) un der one or more2. # contributorlicenseagreements.See the NOTICE file distributed

5、with3. # this work foradditionalinformationregarding copyright own ership.4. # The ASF licenses this file to You under the Apache License, Version2.05. # (the "License");you may notexcept in complia nee withusethisfile6.#theLicense.You may obtainacopyof the Lice nse at7.#8.#/LICENSE-2.09.#

6、10.#Uni essrequired by applicablelaworagreedto in writi ng,software11.#distributedun der the Lice nseisdistributedon an "AS IS" BASIS,12. # WITHOUT WARRANTIESOR CONDITIONS OF ANY KIN D, either express or implied.13. # See the License for the specificIanguagegover ningpermissi onsand14.#lim

7、itati onsun der theLice nse.15.#16.#Listofcomma-separated packagesthatstartwithorequal this stri ng17.#willcause a securityexcepti ontobe thrown when18. # passed to checkPackageAccess uni ess the19. # corresp ondingRun timePermissio n("accessClass InPackage."+package) has20. # bee n gran t

8、ed.21. package.access=s un .,s un .bea ns.22.#23.#Listofcomma-separated packagesthatstartwithorequalthis stri ng24.#willcause asecurityexcepti ontobe thrown when25.# passed to checkPackageDefi niti onuni ess the26. # corresp ondingRun timePermissio n("defi neClass InPackage."+package) has2

9、7. #bee n gran ted.28. #29. #by default, no packages are restricted fordefi niti on,and none of30. #the class loaders supplied with the JDK caIIcheckPackageDefi niti on.31. #32. package.defi niti on=sun .java.,33. #34. #35. #List of comma-separated paths defi ning thecontents of the "com mon&qu

10、ot;36. #classloader. Prefixes should be used to define what is the repository type.37. #Path may berelativeto theCATALINA_HOMEor CATALINA_BASEpath or absolute.38. #If left asblank,theJVM systemloaderwill be used as Catali na's"com mon"39. #loader.40. #Examples:41. #"foo":Add

11、this folder as a classrepository42. #"foo/*.jar":Add all the JARs of the specified folder as class43. #repositories44. #"foo/bar.jar":Add bar.jar as a class repository45. com mon.lo ader=$catali na.home/lib,$catali na.home/lib/*.jar46. #47. #List of comma-separated paths defi nin

12、g thecontents of the "server"48. #classloader. Prefixes should be used to define what is the repository type.49. #Path may be relative to the CATALINA_HOMEor CATALINA_BASEpath or absolute.50. #If left as blank,the "common" loader willbe used as Catali na's "server"5

13、1. #loader.52. #Examples:53. #"foo":Add this folder as a classrepository54. #"foo/*.jar":Add all the JARs of the specified folder as class55. #repositories56. #"foo/bar.jar":Add bar.jar as a class repository57. server.loader=58. #59. # List of comma-separated paths defi

14、 ning the contents of the "shared"60. # classloader. Prefixes should be used to def ine what is the repository type.61. # Path may be relative to the CATALINA_BASE path or absolute. If left as bla nk,62. # the "common" loader will be used as Catalin a's"shared" load

15、er.63. # Examples:64. #"foo":Add this folder as a classrepository65. #"foo/*.jar":Add all the JARs of the specified folder as class66. #repositories67. #"foo/bar.jar":Add bar.jar as a class repository68. # Please n ote that for si ngle jars, e.g. bar .jar, you need the

16、URL form69. # starti ngwith file:.70. shared .lo ader=71. #72. # Stri ng cache con figurati on.73. #74. #75. #此文件，下面會(huì)有詳細(xì)的介紹.OK,到此，我們初步了解到tomcat關(guān)于類加載器的一些知識(shí)鎖定老帖子 主題：Tomcat解析之初始化類加載器（截圖）該帖已經(jīng)被評(píng)為精華帖 作者正文來詳細(xì)看看，tomcat內(nèi)部是怎么來初始化這些類加載器的吧.首先，我們知道，java程序都需要一個(gè)入口 （main方法），而 在tomcat中，這個(gè)入口在這個(gè)類中?？雌浣Y(jié)構(gòu)：定位到萬(wàn)法內(nèi)部：Java代碼門

17、1. public static void main(String args) 2. if(daem on = n ull)3.4.5.源(今天來了解的.10.3. 4. try6.s.le ngth- 1;17.18.)19.daemon = new Bootstrap。；try /初始化資)daem on .i nit(); catch (Throwable t) t.pri ntStackTrace(); return;/默認(rèn)為啟動(dòng)Stri ngcomma nd = "start"if(args .len gth> 0)comm

18、a nd = argsargif(comma nd.equals("startd"argsargsen gth-正文20.1= "start"daem on.lo ad(args);21.daem on. start();22.elseif(comma nd.equals("stopd")23.argsargsen gth-1= "stop"24.daem on. stop();25.elseif(comma nd.equals("start")26./設(shè)置標(biāo)識(shí)27.);daem on. set

19、Await(true28.daem on.lo ad(args);29./開啟30.daem on. start();31.elseif(comma nd.equals("stop")32.daem on. stopServer(args)；33.else34.log.warn("Bootstrap:comma nd ""+comma nd +"" does not exist35.);36.catch(Throwable t) 37.t.pri ntStackTrace();38.39.在tomcat啟動(dòng)之前，需要初始化一

20、些系統(tǒng)資源，初始化的詳細(xì)工作都定義在init()方法內(nèi)部了。0K,我們繼續(xù)追蹤一下。 定位到init()方法中Java代碼笆1. public voidinit()2. throwsExcepti on該帖已經(jīng)被評(píng)為精華帖正文3.4.徑/ SetCatali napath設(shè)置catalina 基本路5.setCatali naHome();6.setCatali naBase();7./初始化類加載器8.in itClassLoaders();9.Thread.curre ntThread().setC on textClassLoader(catali naLoader);10.Securi

21、tyClassLoad.securityClassLoad(catali naLoader);11./ Load our startupclass and call its process() method12.if(log.isDebugE nabled()13.log.debug("Load ingstartup class")14.Jlass("");Class startupClass=catali naLoader.loadC15.Objectstartup In sta nee=startupClass .newIn sta nce();16

22、./ Set the shared exte nsionsclass loader17.if(log.isDebugE nabled()18.log.debug("Sett ingstartup classproperties");19.String methodName = "setPare ntClassLoader20. Class paramTypes = new Class 1;21. paramTypes0 = Class.forName("");22. Object paramValues = new Object 1;23. p

23、aramValues 0= sharedLoader;24. Method method =startupI nsta nce.getClass(). getMethod(methodName, paramTypes);25. method.i nv oke(startup In sta nee,paramValues)26. catali naDaem on= startup In sta nee;27. 可以看到，上面的代碼中，用來初始化類加載器、驗(yàn)證類加載作者正文器、以及使用類加載器來加載類""等等操作。這篇文章，主要來探討一下，tomcat初始化類加載器的方式，所以

24、，我們追蹤到方法in itClassLoaders() 中：這里主要介紹一下，下面的流程，tomcat會(huì)調(diào)用in itClassLoaders()方法。用來初始化commoncatalina,shared三種類加載器，而這個(gè)操作是通過方法createClassLoader(Stri ng n ame, ClassLoader pare nt)來完成的。而后2個(gè)都屬于commons子級(jí)，所以下面給出2個(gè)方法的源代碼(其中相關(guān)信息，都以注釋給出)：Java代碼門1. /*2.*初始化類加載器：3.*加載三種：4.*com mon.5.*/6.*catali nashared.7.*/8.priva

25、te void in itClassLoaders()9.try 10./創(chuàng)建common類加載器11.com mon Loader = createClassLoader("commo n",n ull);12.rif(com mon Loader = null )13./ no config file,default tothisloader - we might be in a'si ngle' mon Loader=this.getClass().getClassLoader();正文15.16./ 倉(cāng)U建 catalina類加載

26、器,指疋其父級(jí)別的加載器為com mon Loader.17.catali naLoader=createClassLoader("server",com mon Loader);18./創(chuàng)建sharedLoader類加載器,指定其父級(jí)別的加載器為commo nLoader.19.sharedLoader =createClassLoader("shared",com mon Loader);20. catch (Throwable t)21.log.error("Classloader creati onthrewexcepti on&quo

27、t;,t);22.System.exit( 1);23.24.Java代碼門1. /*.器.ng10.11.*創(chuàng)建類加載器* param n ame* param pare nt指定上一級(jí)別的類加載* return* throws Exception*/private ClassLoader createClassLoader(Stri n ame, ClassLoader pare nt)throws Excepti on/這里以common例：從catali perties中獲取common.loader類加載信息丿 111、12./ 女口:13.

28、/com mono ader=$catali na.home/lib ,$catali na.home/lib/*.jar14. Stri ng value = Catali naProperties.getPropert y(n ame+ "o ader");15. /如果沒有任何信息，則返回父加載器16.if (valuen ull) | (value.e正文quals("")17.18.ew ArrayList();19.ArrayList();20.21.22.returnpare nt;ArrayListrepositoryLocati ons

29、ArrayListrepositoryTypes=n newint i;/以逗號(hào)分隔.Strin gToke ni zertoke nizernewStri ngToke nizer(value,23. while 24.izer. nextToke n();25.26.",");(toke nizer.hasMoreEleme nts()Stri ng repository = toke n/ Local repository boolea n replace = false;27. Stri ng before= repository;28. /是否含有"$c

30、atali na.home"29.while(i=repository.i ndexOf(CATALINA_HOME_TOKEN)0>= 30.replace=true;31.if (i> 0) 32.tomcat路徑替換后的形式如下： c:/ope nsource/tomcat5/lib./替換成33.repository= repository.substri ng( 0,i)+ getCatali naHome()34.+ repository.substri ng(i+CATALINA_HOME_TOKEN.Ie ngth();35. else 36. repos

31、itory =getCatali naHome()37. + r epository.substri ng(CATALINA_HOME_TOKEN.Ie ngth();38. 39. 40. /是否含有(i=repository.i ndexO replace=true;if (i> 0) /同上，替"$catali na.base"41. while f(CATALINA_BASE_TOKEN)>= 42.43.44.換42. repository = repository.substri ng( 0,i)+ getCatali naBase()43. + r

32、epositor y.substri ng(i+CATALINA_BASE_TOKEN.Ie ngth();44. else 45. repository =getCatali naBase()46. + repository.substri ng(CATALINA_BASE_TOKEN.Ie ngth();50.51.52.gEn abled()if53."+ before+ " to "54.repository/55.try56.pository);57.add(repository);58.ClassLoaderFactory.lS_URL);59.60.

33、tio n e) 61.62.63.jar")if64.itory.substri ng(replace && log.isDebu log.debug("Expa nded+ repository);Check for a JAR URL URL url=new URL(re repositoryLocati ons. repositoryTypes.add( con ti nue;catch (MalformedURLExcep/ Ignore(repository.e ndsWith("*.repository = repos正文65.(0,

34、 repository.le ngth()- "*.jar".le ngth();66.add(repository);repositoryLocati ons.67.ClassLoaderFactory.lS_GLOB);repositoryTypes.add(68. elseif (repository.e ndsWith(".jar")69.add(repository);repositoryLocati ons.70.ClassLoaderFactory.lS_JAR);repositoryTypes.add(71. else72.add(rep

35、ository);repositoryLocati ons.73.ClassLoaderFactory.IS DIR);repositoryTypes.add(74.75.76.Stri nglocati ons= (Stri ng)repositoryLocatio ns.toArray( newString 0);77.In tegertypes=(In teger)repositoryTypes.toArray(newInteger 0);78./創(chuàng)建類加載器79.ClassLoader classLoader = ClassLoaderFactory.createClassLoader

36、80.(locati ons, types, pare nt)81./RetrievingMBean server83.if(MBea nServerFactory.fi ndMBea nServer(n ull).size()> 0)84.mBea nServer =85.(MBea nServer) MBeanServerFactory.fi ndMBea nServer( null).get(0);86. else 87.mBea nServer =Man ageme ntFactory.getPlatformMBea nServer();88.89./ Register the

37、server classload82.MBeanServer mBeanServer = nuII;正文er90. ObjectName objectName =91. new ObjectName("Catalina:ty pe=ServerClassLoader, name=" + n ame);92. mBea nServer.registerMBea n( classLoade r, objectName);93. retur n classLoader;94. 到這里，我們可以確定，tomcat文檔中的類加載器之間關(guān)系是準(zhǔn) 確的，并非憑空說的。到這里，我們可能對(duì)于

38、createClassLoader() 方法的Java代碼門1. CatalinaProperties.getProperty(name+ ".loader");有點(diǎn)疑問，到底tomcat是如果通過配置文件來獲取需要初始化 類加載器的相關(guān)信息的呢/前面我們看到 perties中記錄了 tomcat三種類加載器中分別需要加載一些什么類的信息。而CatalinaProperties類正是用來解析此文件的，以告訴tomcat，哪種類加載器，加載哪些類。我們來看看這個(gè)類的源代碼：Java代碼門總1. /*2. * Utility class to read

39、the bootstrap Catal ina con figurati on.3. * 讀取 tomcat 的配置文件 perties4. * author Remy Maucherat5. * version $Revision: 467222 $ $Date: 2006-10-2411:17:11+0800 (星期二，24 十月 2006)$6. */7. publicclassCatali naProperties8./ -Static Variables9.privatestaticlog=10.Catali naProperties.class);11.pr

40、ivatestaticPropertiespropertiesnull;12.static13.loadProperties();14.15./ -Public Methods16./*17.* Retur nspecifiedproperty value.18.*/19.publicstaticStri nggetProperty(Stri ngn ame)20.retur nproperties.getProperty (n ame)21.J22./*23.* Retur nspecifiedproperty value.24.*/25.publicstaticStri nggetProp

41、erty(Stri ngn ame,Stri ngdefaultValue)26.retur nproperties.getPropert y(n ame,defaultvalue);27.28./ Public Methods29./*30.*加載配置信息31.* Load properties.32.*/33.private staticvoid loadProperties()34.In putStream is = n ull;35.Throwable error = nu II;36./第一步：從系統(tǒng)變量中查找37.try 38./getC on figUrl()方法的內(nèi)容為：Sys

42、tem.getProperty("catali na.c on fig");正文39.Stringcon figUrl= getConfigUrl();40.if(con figUrl!=null)41.is =(newURL(co nfigUrl).ope nStream();42.43.catch(Throwablet) 44./Ignore45.46./第二步：再?gòu)膖omcat的 conf目錄下去找47.if(is :=n ull)48.try 49.Filehome=newFile(getCatali naBase();50.File conf = newFile(

43、home, "co nf");51.File properties=new File(conf."catali perties");52.is = new FileInputStream(properties);53.catch (Throwable t) 54./ Ignore55.56.57./還沒找到:則從類路徑中加載.58.if(is =：=n ull)59. try 60. is =61.("/org/apache/catali na/startup/catali perties");62. catc

44、h (Throwable t) 6.文件中加載過來67./ Ignoreif (is != n ull) /到這里的話，如果找到了，就將配置2.93.該帖已經(jīng)被評(píng)為精華帖正文Properties。;try properties = newproperties .lo ad(is);is.close(); catch (Throwable t) if null) error = t;(is = n ull) | (error !=c

45、atali perties"./ Do something log.war n("Failed error);/ That's fineto load- we have reas on perties=new Properties()統(tǒng)變量./將配置文件的key-value 設(shè)置為系/ Register the properties as system properties=propertEnu merati onenu meratio pertyNames();while(enu merati on .h

46、asMoreEleme nts()String n ame = (Stri ng)enu merati on.n extEleme nt();Stri ngvalue = properties.getPropert y(n ame);if (value != n ull) System.setProperty(name, value);/*en vir onmentvariable.95.*/96.privatestaticStri ng getCatali naHome()97.returnSystem.getProperty("catali na.home",98.Sy

47、stem.getProperty("user.dir");94.Get the value of the catalina.home99.100./*101.* Get thevalue ofthe catali na.baseen vir onmentvariable.102.*/103.privatestaticStri nggetCatali naBase()104.returnSystem.getProperty("catalin a.base",getCatali naHome();105.106./*107.* Get thevalue ofthe con figuratio nURL.108.*/109.privatestaticStri nggetC