报错问题
前几天手贱下载了一个jdk17并安装了，升级后有一些软件打不开了，比如monitor等，报错如下：
!SESSION 2022-03-28 14:48:05.075 -----------------------------------------------
eclipse.buildId=unknown
java.version=17.0.1
java.vendor=Oracle Corporation
BootLoader constants: OS=macosx, ARCH=x86_64, WS=cocoa, NL=zh_CN_#Hans
Framework arguments: -keyring /Users/ygs/.eclipse_keyring -showlocation
Command-line arguments: -os macosx -ws cocoa -arch x86_64 -data @noDefault -keyring /Users/ygs/.eclipse_keyring -showlocation
!ENTRY org.eclipse.osgi 4 0 2022-03-28 14:48:05.307
!MESSAGE error loading hook: org.eclipse.osgi.internal.baseadaptor.BaseHookConfigurator
!STACK 0
java.lang.reflect.InaccessibleObjectException: Unable to make protected void java.net.URLClassLoader.addURL(java.net.URL) accessible: module java.base does not "opens java.net" to unnamed module @47fd17e3
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
at org.eclipse.osgi.internal.baseadaptor.BaseStorage.findMethod(BaseStorage.java:174)
at org.eclipse.osgi.internal.baseadaptor.BaseStorage.findMethod(BaseStorage.java:181)
at org.eclipse.osgi.internal.baseadaptor.BaseStorage.findAddURLMethod(BaseStorage.java:165)
at org.eclipse.osgi.internal.baseadaptor.BaseStorage.<init>(BaseStorage.java:135)
at org.eclipse.osgi.internal.baseadaptor.BaseHookConfigurator.addHooks(BaseHookConfigurator.java:24)
at org.eclipse.osgi.baseadaptor.HookRegistry.loadConfigurators(HookRegistry.java:178)
at org.eclipse.osgi.baseadaptor.HookRegistry.initialize(HookRegistry.java:100)
at org.eclipse.osgi.baseadaptor.BaseAdaptor.<init>(BaseAdaptor.java:98)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
at org.eclipse.core.runtime.adaptor.EclipseStarter.createAdaptor(EclipseStarter.java:737)
at org.eclipse.core.runtime.adaptor.EclipseStarter.startup(EclipseStarter.java:258)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:176)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
!ENTRY org.eclipse.osgi 4 0 2022-03-28 14:48:05.344
!MESSAGE Startup error
!STACK 1
java.lang.NullPointerException: Cannot invoke "org.eclipse.osgi.internal.baseadaptor.BaseStorage.initialize(org.eclipse.osgi.baseadaptor.BaseAdaptor)" because "this.storage" is null
at org.eclipse.osgi.baseadaptor.BaseAdaptor.initializeStorage(BaseAdaptor.java:123)
at org.eclipse.osgi.framework.internal.core.Framework.<init>(Framework.java:192)
at org.eclipse.core.runtime.adaptor.EclipseStarter.startup(EclipseStarter.java:262)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:176)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
觉得问题不大，于是就在.zshrc(.bashrc)中切换成jdk1.8结果还是不行，报一样的错，明明已经切换了，为什么还是用的17的jdk了，切换 Shell 的 JDK到指定版本竟然不管用。
export JAVA_8_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home"
alias jdk8='export JAVA_HOME=$JAVA_8_HOME'
export JAVA_17_HOME="/Library/Java/JavaVirtualMachines/jdk-17.0.1.jdk/Contents/Home"
alias jdk17='export JAVA_HOME=$JAVA_17_HOME'
export JAVA_HOME=$JAVA_8_HOME
如何解决
后来觉的是有些程序默认用的jdk是 /usr/libexec/java_home -V 中看到的最高版本。也就是全局环境变量我们没有修改。
~ /usr/libexec/java_home -V
Matching Java Virtual Machines (3):
17.0.1 (x86_64) "Oracle Corporation" - "Java SE 17.0.1" /Library/Java/JavaVirtualMachines/jdk-17.0.1.jdk/Contents/Home
1.8.0_131 (x86_64) "Oracle Corporation" - "Java SE 8"
我这里是安装了jdk17，所以默认就使用了jdk17.
我们可以通过修改版本号实现指定版本的JDK做为默认JDK,/usr/libexec/java_home是通过/Library/Java/JavaVirtualMachines/<JDK>/Contents/Info.plist里的JVMVersion值来获取版本号的，所以只需要修改这个值为当前最大版本号即可实现指定默认 JDK。经过测试这个还是即时生效
我这里把/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Info.plist中的JVMVersion的值由1.8.0_131改为88.8.0_131(大概在40行)，这样我们的jdk1.8就会排到第一位，排序是安装数字大小来排序的。再次打开monitor就可以了
~ /usr/libexec/java_home -V
Matching Java Virtual Machines (3):
88.8.0_131 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home
17.0.1 (x86_64) "Oracle Corporation" - "Java SE 17.0.1" /Library/Java/JavaVirtualMachines/jdk-17.0.1.jdk/Contents/Home
