Ant的实现原理
在build.xml中，我们使用一句简单的脚本就可以执行想要做的事情，比如说：
<delete dir="d://testMKDir" />
上面这句脚本将删除 d://testMKDir
很神奇，有木有？
想知道怎么实现的吗？
继续往下看....
将ant.jar反编译一下，我看看到如下东东：
原来ant将这些操作都封装了起来。这些操作都有一个共通的基类叫Task(抽象类)。
public void execute() throws BuildException{ }
其中有个空实现的execute方法，为什么提这个，后面你就知道了。
下面来测试一下：
/* * <delete dir="d://testMKDir" /> * <mkdir dir="d://testMKDir" /> * delete=org.apache.tools.ant.taskdefs.Delete * mkdir=org.apache.tools.ant.taskdefs.Mkdir */public static void execute(String obj, String path) { try { Method setMethod = null; Class classObj = Class.forName(obj); Object objectCopy = classObj.getConstructor(new Class[] {}) .newInstance(new Object[] {}); setMethod = classObj.getMethod("setDir", new Class[] { File.class }); setMethod.invoke(objectCopy, new File(path)); Task task = (Task) objectCopy; task.execute(); } catch (Exception e) { System.out.println(e); } }
调用上面的方法：
execute("org.apache.tools.ant.taskdefs.Mkdir", "d://testMKDir");
execute("org.apache.tools.ant.taskdefs.Delete", "d://testMKDir");
执行之后，控制台输出：
Created dir: d:\testMKDir
Deleting directory d:\testMKDir
由上可知，build.xml中的执行过程大致为：
以解析<mkdir dir = "d://testMKDir" />为例：
- 解析到了mkdir，就根据属性文件defaults.properties查找到： mkdir=org.apache.tools.ant.taskdefs.Mkdir
- 通过反射创建org.apache.tools.ant.taskdefs.Mkdir对象
- 获取其属性比如File dir;
- 根据属性设置方法setDir(File dir);
- 最后用其父类调用execute()方法
defaults.properties文件在org.apache.tools.ant.types包下，内容如下：
defaults.properties
1 # Licensed to the Apache Software Foundation (ASF) under one or more 2 # contributor license agreements. See the NOTICE file distributed with 3 # this work for additional information regarding copyright ownership. 4 # The ASF licenses this file to You under the Apache License, Version 2.0 5 # (the "License"); you may not use this file except in compliance with 6 # the License. You may obtain a copy of the License at 7 # 8 # http://www.apache.org/licenses/LICENSE-2.0 9 # 10 # Unless required by applicable law or agreed to in writing, software 11 # distributed under the License is distributed on an "AS IS" BASIS, 12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 # See the License for the specific language governing permissions and 14 # limitations under the License. 15 # 16 # standard ant tasks 17 ant=org.apache.tools.ant.taskdefs.Ant 18 antcall=org.apache.tools.ant.taskdefs.CallTarget 19 antstructure=org.apache.tools.ant.taskdefs.AntStructure 20 antversion=org.apache.tools.ant.taskdefs.condition.AntVersion 21 apply=org.apache.tools.ant.taskdefs.Transform 22 available=org.apache.tools.ant.taskdefs.Available 23 basename=org.apache.tools.ant.taskdefs.Basename 24 buildnumber=org.apache.tools.ant.taskdefs.BuildNumber 25 bunzip2=org.apache.tools.ant.taskdefs.BUnzip2 26 bzip2=org.apache.tools.ant.taskdefs.BZip2 27 checksum=org.apache.tools.ant.taskdefs.Checksum 28 chmod=org.apache.tools.ant.taskdefs.Chmod 29 classloader=org.apache.tools.ant.taskdefs.Classloader 30 concat=org.apache.tools.ant.taskdefs.Concat 31 condition=org.apache.tools.ant.taskdefs.ConditionTask 32 copy=org.apache.tools.ant.taskdefs.Copy 33 cvs=org.apache.tools.ant.taskdefs.Cvs 34 cvschangelog=org.apache.tools.ant.taskdefs.cvslib.ChangeLogTask 35 cvspass=org.apache.tools.ant.taskdefs.CVSPass 36 cvstagdiff=org.apache.tools.ant.taskdefs.cvslib.CvsTagDiff 37 cvsversion=org.apache.tools.ant.taskdefs.cvslib.CvsVersion 38 defaultexcludes=org.apache.tools.ant.taskdefs.DefaultExcludes 39 delete=org.apache.tools.ant.taskdefs.Delete 40 dependset=org.apache.tools.ant.taskdefs.DependSet 41 diagnostics=org.apache.tools.ant.taskdefs.DiagnosticsTask 42 dirname=org.apache.tools.ant.taskdefs.Dirname 43 ear=org.apache.tools.ant.taskdefs.Ear 44 echo=org.apache.tools.ant.taskdefs.Echo 45 exec=org.apache.tools.ant.taskdefs.ExecTask 46 fail=org.apache.tools.ant.taskdefs.Exit 47 filter=org.apache.tools.ant.taskdefs.Filter 48 fixcrlf=org.apache.tools.ant.taskdefs.FixCRLF 49 genkey=org.apache.tools.ant.taskdefs.GenerateKey 50 get=org.apache.tools.ant.taskdefs.Get 51 gunzip=org.apache.tools.ant.taskdefs.GUnzip 52 gzip=org.apache.tools.ant.taskdefs.GZip 53 import=org.apache.tools.ant.taskdefs.ImportTask 54 input=org.apache.tools.ant.taskdefs.Input 55 jar=org.apache.tools.ant.taskdefs.Jar 56 java=org.apache.tools.ant.taskdefs.Java 57 javac=org.apache.tools.ant.taskdefs.Javac 58 javadoc=org.apache.tools.ant.taskdefs.Javadoc 59 length=org.apache.tools.ant.taskdefs.Length 60 loadfile=org.apache.tools.ant.taskdefs.LoadFile 61 loadproperties=org.apache.tools.ant.taskdefs.LoadProperties 62 loadresource=org.apache.tools.ant.taskdefs.LoadResource 63 macrodef=org.apache.tools.ant.taskdefs.MacroDef 64 mail=org.apache.tools.ant.taskdefs.email.EmailTask 65 manifest=org.apache.tools.ant.taskdefs.ManifestTask 66 manifestclasspath=org.apache.tools.ant.taskdefs.ManifestClassPath 67 mkdir=org.apache.tools.ant.taskdefs.Mkdir 68 move=org.apache.tools.ant.taskdefs.Move 69 nice=org.apache.tools.ant.taskdefs.Nice 70 parallel=org.apache.tools.ant.taskdefs.Parallel 71 patch=org.apache.tools.ant.taskdefs.Patch 72 pathconvert=org.apache.tools.ant.taskdefs.PathConvert 73 presetdef=org.apache.tools.ant.taskdefs.PreSetDef 74 property=org.apache.tools.ant.taskdefs.Property 75 record=org.apache.tools.ant.taskdefs.Recorder 76 replace=org.apache.tools.ant.taskdefs.Replace 77 retry=org.apache.tools.ant.taskdefs.Retry 78 rmic=org.apache.tools.ant.taskdefs.Rmic 79 sequential=org.apache.tools.ant.taskdefs.Sequential 80 signjar=org.apache.tools.ant.taskdefs.SignJar 81 sleep=org.apache.tools.ant.taskdefs.Sleep 82 sql=org.apache.tools.ant.taskdefs.SQLExec 83 subant=org.apache.tools.ant.taskdefs.SubAnt 84 sync=org.apache.tools.ant.taskdefs.Sync 85 tar=org.apache.tools.ant.taskdefs.Tar 86 taskdef=org.apache.tools.ant.taskdefs.Taskdef 87 tempfile=org.apache.tools.ant.taskdefs.TempFile 88 touch=org.apache.tools.ant.taskdefs.Touch 89 tstamp=org.apache.tools.ant.taskdefs.Tstamp 90 truncate=org.apache.tools.ant.taskdefs.Truncate 91 typedef=org.apache.tools.ant.taskdefs.Typedef 92 unjar=org.apache.tools.ant.taskdefs.Expand 93 untar=org.apache.tools.ant.taskdefs.Untar 94 unwar=org.apache.tools.ant.taskdefs.Expand 95 unzip=org.apache.tools.ant.taskdefs.Expand 96 uptodate=org.apache.tools.ant.taskdefs.UpToDate 97 waitfor=org.apache.tools.ant.taskdefs.WaitFor 98 war=org.apache.tools.ant.taskdefs.War 99 whichresource=org.apache.tools.ant.taskdefs.WhichResource 100 xmlproperty=org.apache.tools.ant.taskdefs.XmlProperty 101 xslt=org.apache.tools.ant.taskdefs.XSLTProcess 102 zip=org.apache.tools.ant.taskdefs.Zip 103 104 # optional tasks 105 antlr=org.apache.tools.ant.taskdefs.optional.ANTLR 106 apt=org.apache.tools.ant.taskdefs.Apt 107 attrib=org.apache.tools.ant.taskdefs.optional.windows.Attrib 108 blgenclient=org.apache.tools.ant.taskdefs.optional.ejb.BorlandGenerateClient 109 cab=org.apache.tools.ant.taskdefs.optional.Cab 110 cccheckin=org.apache.tools.ant.taskdefs.optional.clearcase.CCCheckin 111 cccheckout=org.apache.tools.ant.taskdefs.optional.clearcase.CCCheckout 112 cclock=org.apache.tools.ant.taskdefs.optional.clearcase.CCLock 113 ccmcheckin=org.apache.tools.ant.taskdefs.optional.ccm.CCMCheckin 114 ccmcheckintask=org.apache.tools.ant.taskdefs.optional.ccm.CCMCheckinDefault 115 ccmcheckout=org.apache.tools.ant.taskdefs.optional.ccm.CCMCheckout 116 ccmcreatetask=org.apache.tools.ant.taskdefs.optional.ccm.CCMCreateTask 117 ccmkattr=org.apache.tools.ant.taskdefs.optional.clearcase.CCMkattr 118 ccmkbl=org.apache.tools.ant.taskdefs.optional.clearcase.CCMkbl 119 ccmkdir=org.apache.tools.ant.taskdefs.optional.clearcase.CCMkdir 120 ccmkelem=org.apache.tools.ant.taskdefs.optional.clearcase.CCMkelem 121 ccmklabel=org.apache.tools.ant.taskdefs.optional.clearcase.CCMklabel 122 ccmklbtype=org.apache.tools.ant.taskdefs.optional.clearcase.CCMklbtype 123 ccmreconfigure=org.apache.tools.ant.taskdefs.optional.ccm.CCMReconfigure 124 ccrmtype=org.apache.tools.ant.taskdefs.optional.clearcase.CCRmtype 125 ccuncheckout=org.apache.tools.ant.taskdefs.optional.clearcase.CCUnCheckout 126 ccunlock=org.apache.tools.ant.taskdefs.optional.clearcase.CCUnlock 127 ccupdate=org.apache.tools.ant.taskdefs.optional.clearcase.CCUpdate 128 chgrp=org.apache.tools.ant.taskdefs.optional.unix.Chgrp 129 chown=org.apache.tools.ant.taskdefs.optional.unix.Chown 130 csc=org.apache.tools.ant.taskdefs.optional.dotnet.CSharp 131 ddcreator=org.apache.tools.ant.taskdefs.optional.ejb.DDCreator 132 depend=org.apache.tools.ant.taskdefs.optional.depend.Depend 133 echoproperties=org.apache.tools.ant.taskdefs.optional.EchoProperties 134 echoxml=org.apache.tools.ant.taskdefs.EchoXML 135 ejbc=org.apache.tools.ant.taskdefs.optional.ejb.Ejbc 136 ejbjar=org.apache.tools.ant.taskdefs.optional.ejb.EjbJar 137 ftp=org.apache.tools.ant.taskdefs.optional.net.FTP 138 ilasm=org.apache.tools.ant.taskdefs.optional.dotnet.Ilasm 139 ildasm=org.apache.tools.ant.taskdefs.optional.dotnet.Ildasm 140 image=org.apache.tools.ant.taskdefs.optional.image.Image 141 importtypelib=org.apache.tools.ant.taskdefs.optional.dotnet.ImportTypelib 142 iplanet-ejbc=org.apache.tools.ant.taskdefs.optional.ejb.IPlanetEjbcTask 143 jarlib-available=org.apache.tools.ant.taskdefs.optional.extension.JarLibAvailableTask 144 jarlib-display=org.apache.tools.ant.taskdefs.optional.extension.JarLibDisplayTask 145 jarlib-manifest=org.apache.tools.ant.taskdefs.optional.extension.JarLibManifestTask 146 jarlib-resolve=org.apache.tools.ant.taskdefs.optional.extension.JarLibResolveTask 147 javacc=org.apache.tools.ant.taskdefs.optional.javacc.JavaCC 148 javah=org.apache.tools.ant.taskdefs.optional.Javah 149 jdepend=org.apache.tools.ant.taskdefs.optional.jdepend.JDependTask 150 jjdoc=org.apache.tools.ant.taskdefs.optional.javacc.JJDoc 151 jjtree=org.apache.tools.ant.taskdefs.optional.javacc.JJTree 152 jsharpc=org.apache.tools.ant.taskdefs.optional.dotnet.JSharp 153 junit=org.apache.tools.ant.taskdefs.optional.junit.JUnitTask 154 junitreport=org.apache.tools.ant.taskdefs.optional.junit.XMLResultAggregator 155 makeurl=org.apache.tools.ant.taskdefs.MakeUrl 156 native2ascii=org.apache.tools.ant.taskdefs.optional.Native2Ascii 157 netrexxc=org.apache.tools.ant.taskdefs.optional.NetRexxC 158 p4add=org.apache.tools.ant.taskdefs.optional.perforce.P4Add 159 p4change=org.apache.tools.ant.taskdefs.optional.perforce.P4Change 160 p4counter=org.apache.tools.ant.taskdefs.optional.perforce.P4Counter 161 p4delete=org.apache.tools.ant.taskdefs.optional.perforce.P4Delete 162 p4edit=org.apache.tools.ant.taskdefs.optional.perforce.P4Edit 163 p4fstat=org.apache.tools.ant.taskdefs.optional.perforce.P4Fstat 164 p4have=org.apache.tools.ant.taskdefs.optional.perforce.P4Have 165 p4integrate=org.apache.tools.ant.taskdefs.optional.perforce.P4Integrate 166 p4label=org.apache.tools.ant.taskdefs.optional.perforce.P4Label 167 p4labelsync=org.apache.tools.ant.taskdefs.optional.perforce.P4Labelsync 168 p4reopen=org.apache.tools.ant.taskdefs.optional.perforce.P4Reopen 169 p4resolve=org.apache.tools.ant.taskdefs.optional.perforce.P4Resolve 170 p4revert=org.apache.tools.ant.taskdefs.optional.perforce.P4Revert 171 p4submit=org.apache.tools.ant.taskdefs.optional.perforce.P4Submit 172 p4sync=org.apache.tools.ant.taskdefs.optional.perforce.P4Sync 173 propertyfile=org.apache.tools.ant.taskdefs.optional.PropertyFile 174 pvcs=org.apache.tools.ant.taskdefs.optional.pvcs.Pvcs 175 replaceregexp=org.apache.tools.ant.taskdefs.optional.ReplaceRegExp 176 resourcecount=org.apache.tools.ant.taskdefs.ResourceCount 177 rexec=org.apache.tools.ant.taskdefs.optional.net.RExecTask 178 rpm=org.apache.tools.ant.taskdefs.optional.Rpm 179 schemavalidate=org.apache.tools.ant.taskdefs.optional.SchemaValidate 180 scp=org.apache.tools.ant.taskdefs.optional.ssh.Scp 181 script=org.apache.tools.ant.taskdefs.optional.Script 182 scriptdef=org.apache.tools.ant.taskdefs.optional.script.ScriptDef 183 serverdeploy=org.apache.tools.ant.taskdefs.optional.j2ee.ServerDeploy 184 setproxy=org.apache.tools.ant.taskdefs.optional.net.SetProxy 185 soscheckin=org.apache.tools.ant.taskdefs.optional.sos.SOSCheckin 186 soscheckout=org.apache.tools.ant.taskdefs.optional.sos.SOSCheckout 187 sosget=org.apache.tools.ant.taskdefs.optional.sos.SOSGet 188 soslabel=org.apache.tools.ant.taskdefs.optional.sos.SOSLabel 189 sound=org.apache.tools.ant.taskdefs.optional.sound.SoundTask 190 splash=org.apache.tools.ant.taskdefs.optional.splash.SplashTask 191 sshexec=org.apache.tools.ant.taskdefs.optional.ssh.SSHExec 192 stcheckin=org.apache.tools.ant.taskdefs.optional.starteam.StarTeamCheckin 193 stcheckout=org.apache.tools.ant.taskdefs.optional.starteam.StarTeamCheckout 194 stlabel=org.apache.tools.ant.taskdefs.optional.starteam.StarTeamLabel 195 stlist=org.apache.tools.ant.taskdefs.optional.starteam.StarTeamList 196 stylebook=org.apache.tools.ant.taskdefs.optional.StyleBook 197 symlink=org.apache.tools.ant.taskdefs.optional.unix.Symlink 198 telnet=org.apache.tools.ant.taskdefs.optional.net.TelnetTask 199 translate=org.apache.tools.ant.taskdefs.optional.i18n.Translate 200 vbc=org.apache.tools.ant.taskdefs.optional.dotnet.VisualBasicCompile 201 verifyjar=org.apache.tools.ant.taskdefs.VerifyJar 202 vssadd=org.apache.tools.ant.taskdefs.optional.vss.MSVSSADD 203 vsscheckin=org.apache.tools.ant.taskdefs.optional.vss.MSVSSCHECKIN 204 vsscheckout=org.apache.tools.ant.taskdefs.optional.vss.MSVSSCHECKOUT 205 vsscp=org.apache.tools.ant.taskdefs.optional.vss.MSVSSCP 206 vsscreate=org.apache.tools.ant.taskdefs.optional.vss.MSVSSCREATE 207 vssget=org.apache.tools.ant.taskdefs.optional.vss.MSVSSGET 208 vsshistory=org.apache.tools.ant.taskdefs.optional.vss.MSVSSHISTORY 209 vsslabel=org.apache.tools.ant.taskdefs.optional.vss.MSVSSLABEL 210 wljspc=org.apache.tools.ant.taskdefs.optional.jsp.WLJspc 211 wlrun=org.apache.tools.ant.taskdefs.optional.ejb.WLRun 212 wlstop=org.apache.tools.ant.taskdefs.optional.ejb.WLStop 213 wsdltodotnet=org.apache.tools.ant.taskdefs.optional.dotnet.WsdlToDotnet 214 xmlvalidate=org.apache.tools.ant.taskdefs.optional.XMLValidateTask 215 216 217 # deprecated ant tasks (kept for back compatibility) 218 copydir=org.apache.tools.ant.taskdefs.Copydir 219 copyfile=org.apache.tools.ant.taskdefs.Copyfile 220 copypath=org.apache.tools.ant.taskdefs.CopyPath 221 deltree=org.apache.tools.ant.taskdefs.Deltree 222 execon=org.apache.tools.ant.taskdefs.ExecuteOn 223 javadoc2=org.apache.tools.ant.taskdefs.Javadoc 224 jlink=org.apache.tools.ant.taskdefs.optional.jlink.JlinkTask 225 jspc=org.apache.tools.ant.taskdefs.optional.jsp.JspC 226 mimemail=org.apache.tools.ant.taskdefs.optional.net.MimeMail 227 rename=org.apache.tools.ant.taskdefs.Rename 228 renameext=org.apache.tools.ant.taskdefs.optional.RenameExtensions 229 starteam=org.apache.tools.ant.taskdefs.optional.scm.AntStarTeamCheckOut 230 style=org.apache.tools.ant.taskdefs.XSLTProcess 231 WsdlToDotnet=org.apache.tools.ant.taskdefs.optional.dotnet.WsdlToDotnet
类似的，测试一下copy方法如下：
public static void execute_Copy(String obj, String path,String destPath) { try { Method setMethod = null; Method setDestMethod = null; Class classObj = Class.forName(obj); Object objectCopy = classObj.getConstructor(new Class[] {}) .newInstance(new Object[] {}); setMethod = classObj.getMethod("setFile", new Class[] { File.class }); setMethod.invoke(objectCopy, new File(path)); setDestMethod = classObj.getMethod("setTofile", new Class[] { File.class }); setDestMethod.invoke(objectCopy, new File(destPath)); Task task = (Task) objectCopy; task.execute(); } catch (Exception e) { System.out.println(e); } }
以上测试基于ant 1.7版，其他版本应该也差不多..