升级到Java7，Missing Tools.jar和错误的类版本后，构建失败

Question

我最近在Macbook Pro上升级到Java7。我下载了JDK（不是JRE）。

» javac version
javac 1.7.0_17

» echo $JAVA_HOME    
/Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk/Contents/Home

但是，当尝试运行构建时，maven编译器插件之一失败了，并声称我安装了JRE：

» mvn install
[ERROR] execute error
org.apache.maven.plugin.MojoExecutionException: You need to run build with JDK
 or have tools.jar on the classpath.
If this occures during eclipse build make sure you run eclipse under JDK as well
    at com.mysema.maven.apt.AbstractProcessorMojo.execute(AbstractProcessorMojo.java:263)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)

我很困惑，因为我显然已经安装了JDK。我MAVEN_OPTS不要做任何有趣的事：

» echo $MAVEN_OPTS          
-Xmx512m

尝试调试时，我检查了相关插件的来源，该插件正在执行以下操作：

    try {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        if (compiler == null) {
            throw new MojoExecutionException("You need to run build with JDK or have tools.jar on the classpath."
                    + "If this occures during eclipse build make sure you run eclipse under JDK as well");
        }

这似乎无害，所以我怀疑我的命令行环境中有问题，并编写了一个简单的测试：

// Main.java
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;


public class Main {

    public static void main(String[] args) {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        if (compiler == null)
        {
            System.out.print("Compiler is null");
        } else {
            System.out.print("Compiler is not null");
        }
    }

}

» javac Main.java

Main.java:1: cannot access javax.tools.JavaCompiler
bad class file: /Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk/Contents/Home/jre/lib/rt.jar(javax/tools/JavaCompiler.class)
class file has wrong version 51.0, should be 49.0
Please remove or make sure it appears in the correct subdirectory of the classpath.
import javax.tools.JavaCompiler;
                   ^
1 error

如果我正确理解该错误，则表明它是针对Java5运行的Java7编译器rt.jar？

我不确定这是怎么回事。

我显然已经安装了Java7 JDK，但不了解：

• 为什么Maven插件为编译器返回null？
• 为什么会出现类版本错误？

更新资料

答案表明，JRE / JDK安装混乱。我同意这似乎是可能的，但是在追查罪魁祸首的位置时遇到了麻烦。

一些其他信息：

» which javac
/usr/bin/javac

ls -ltra /usr/bin/javac
/usr/bin/javac -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/javac

cd /System/Library/Frameworks/JavaVM.framework/Versions
ls -ltra

lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.6.0 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.6 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.5.0 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.5 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.4.2 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.4 -> CurrentJDK
drwxr-xr-x   8 root  wheel  272 18 Feb 08:39 A
drwxr-xr-x  11 root  wheel  374 18 Feb 08:39 ..
lrwxr-xr-x   1 root  wheel    1 14 Jun 11:14 Current -> A
lrwxr-xr-x   1 root  wheel   58 14 Jun 11:15 CurrentJDK -> /Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk/Contents
drwxr-xr-x  11 root  wheel  374 14 Jun 11:15 .

因此，正在运行的javac是安装在中的javac
A/Commands。我不确定这是否正确。从我的Windows时代看来，这似乎是错误的，但是我对Mac如何对待Java安装进行修补还不太熟悉。

我$JAVA_HOME指向/Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk/Contents/Home，它具有以下内容：

drwxrwxr-x  10 root  wheel       340  5 Feb 08:10 jre
-rw-rw-r--   1 root  wheel    123324  5 Feb 08:10 THIRDPARTYLICENSEREADME-JAVAFX.txt
drwxrwxr-x   5 root  wheel       170  5 Feb 08:10 man
drwxrwxr-x   9 root  wheel       306  2 Mar 02:10 db
-rw-rw-r--   1 root  wheel      3339  2 Mar 02:10 COPYRIGHT
drwxrwxr-x   9 root  wheel       306  2 Mar 02:10 include
-rw-rw-r--   1 root  wheel  19997030  2 Mar 02:10 src.zip
-rw-rw-r--   1 root  wheel       447  2 Mar 02:10 release
-rw-rw-r--   1 root  wheel    172252  2 Mar 02:10 THIRDPARTYLICENSEREADME.txt
-rw-rw-r--   1 root  wheel       114  2 Mar 02:10 README.html
-rw-rw-r--   1 root  wheel        40  2 Mar 02:10 LICENSE
drwxrwxr-x   5 root  wheel       170  2 Mar 02:10 ..
drwxrwxr-x  15 root  wheel       510  2 Mar 02:13 .
drwxrwxr-x  13 root  wheel       442  2 Mar 02:13 lib
drwxrwxr-x  43 root  wheel      1462  2 Mar 02:13 bin

Answer 1

我发现tools.jar坐在/Library/Java/Extensions

我不确定这是否是标准的。

但是，tools.jar从JDK7 复制$JAVA_HOME/lib可以/Library/Java/Extensions解决我所有的问题。

我还应该指出，在我最初的问题中，我已将Java更新CurrentSDK为JDK7：

CurrentJDK -> /Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk/Contents

正如这里指出的，这是一个坏主意。

我将其更新为指向1.6。尽管这似乎违反直觉，但仍需要使事情正常进行。

/System/Library/Frameworks/JavaVM.framework/Versions使用1.7JDK 的当前列表如下：

lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.6.0 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.6 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.5.0 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.5 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.4.2 -> CurrentJDK
lrwxr-xr-x   1 root  wheel   10 18 Feb 08:36 1.4 -> CurrentJDK
drwxr-xr-x   8 root  wheel  272 18 Feb 08:39 A
drwxr-xr-x  11 root  wheel  374 18 Feb 08:39 ..
lrwxr-xr-x   1 root  wheel    1 14 Jun 11:35 Current -> A
lrwxr-xr-x   1 root  wheel   59 14 Jun 12:31 CurrentJDK -> /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents
drwxr-xr-x  11 root  wheel  374 14 Jun 12:31 .