Ant Unable to find a javac compiler Perhaps JAVA_HOME does not point to the JDK 解决办法

今天在使用Ant 多渠道批量打包的时候，Ant打包程序一直报错，日志信息如下：

F:\soft\android-sdk-windows\android-sdk-windows\tools\ant\build.xml:713: The following error occurred while executing this line:
F:\soft\android-sdk-windows\android-sdk-windows\tools\ant\build.xml:727: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre7"
at org.apache.tools.ant.ProjectHelper.addLocationToBuildException(ProjectHelper.java:568)
at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:399)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.Target.execute(Target.java:435)
at org.apache.tools.ant.Target.performTasks(Target.java:456)
at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1393)
at org.apache.tools.ant.Project.executeTarget(Project.java:1364)
at com.open.antbuild.AntTest0.runTarget(AntTest0.java:93)
at com.open.antbuild.AntTest0.buildApk(AntTest0.java:141)
at com.open.antbuild.AntTest0.main(AntTest0.java:41)
Caused by: F:\soft\android-sdk-windows\android-sdk-windows\tools\ant\build.xml:727: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre7"
at org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.getCompiler(CompilerAdapterFactory.java:129)
at org.apache.tools.ant.taskdefs.Javac.findSupportedFileExtensions(Javac.java:979)
at org.apache.tools.ant.taskdefs.Javac.scanDir(Javac.java:956)
at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:927)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:68)
at com.android.ant.IfElseTask.execute(IfElseTask.java:120)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:68)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:396)
... 13 more


大概意思是JAVA_HOME没有指向JDK安装目录，可是我明明都配置好了JAVA_HOME

java -version



javac 命令



echo %JAVA_HOME% 命令



检查完了都没问题，可是一运行程序还是会出现错误：

Unable to find a javac compiler;

com.sun.tools.javac.Main is not on the classpath.

Perhaps JAVA_HOME does not point to the JDK.

最后Google找到了解决办法，就是把JDK/lib 目录下的tool.jar添加到build path，如下图所示：



再次运行Ant打包程序就没问题啦！