setUncaughtExceptionHandler在Maven項目中不工作

我想在我的應用程序的主線程上處理未捕獲的異常，因此我可以將它們記錄到文件中（我的應用程序是一個命令行應用程序，出現錯誤我希望管理員能夠輕鬆查看例外情況）。我儘可能簡化了測試用例。setUncaughtExceptionHandler在Maven項目中不工作

mvn -B archetype:generate \ 
     -DarchetypeGroupId=org.apache.maven.archetypes \ 
     -DgroupId=com.mycompany.app \ 
     -DartifactId=my-app

App.java：與（按照getting started docs）產生

Maven的應用

package com.mycompany.app; 

public class App { 

    public static void main(String[] args) throws Exception { 
     Thread.currentThread().setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { 
      public void uncaughtException(Thread t, Throwable e) { 
       System.out.println("Handled exception - let's log it!"); 
       // Logging code here 
      } 
     }); 

     System.out.println("Exception testing"); 
     throw new Exception("Catch and log me!"); 
    } 

}

與mvn exec:java運行生產：

[INFO] Error stacktraces are turned on. 
[INFO] Scanning for projects... 
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for com.mycompany.app:my-app:jar:1.0-SNAPSHOT 
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:exec-maven-plugin is missing. @ line 20, column 15 
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build. 
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects. 
[WARNING] 
[INFO]                   
[INFO] ------------------------------------------------------------------------ 
[INFO] Building my-app 1.0-SNAPSHOT 
[INFO] ------------------------------------------------------------------------ 
[INFO] 
[INFO] --- exec-maven-plugin:1.4.0:java (default-cli) @ my-app --- 
Exception testing 
[WARNING] 
java.lang.reflect.InvocationTargetException 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:606) 
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:293) 
    at java.lang.Thread.run(Thread.java:745) 
Caused by: java.lang.Exception: Catch and log me! 
    at com.mycompany.app.App.main(App.java:14) 
    ... 6 more 
[INFO] ------------------------------------------------------------------------ 
[INFO] BUILD FAILURE 
[INFO] ------------------------------------------------------------------------ 
[INFO] Total time: 0.493 s 
[INFO] Finished at: 2015-10-26T10:57:00+00:00 
[INFO] Final Memory: 8M/240M 
[INFO] ------------------------------------------------------------------------ 
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java (default-cli) on project my-app: An exception occured while executing the Java class. null: InvocationTargetException: Catch and log me! -> [Help 1] 
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java (default-cli) on project my-app: An exception occured while executing the Java class. null 
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216) 
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153) 
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145) 
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116) 
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80) 
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51) 
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128) 
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307) 
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193) 
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106) 
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862) 
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286) 
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:197) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:606) 
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289) 
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229) 
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415) 
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356) 
Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. null 
    at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:345) 
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134) 
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208) 
    ... 20 more 
Caused by: java.lang.reflect.InvocationTargetException 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:606) 
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:293) 
    at java.lang.Thread.run(Thread.java:745) 
Caused by: java.lang.Exception: Catch and log me! 
    at com.mycompany.app.App.main(App.java:14) 
    ... 6 more

相同的代碼運行作爲一個簡單的Java應用程序工作正常App.java：

public class App { 

    public static void main(String[] args) throws Exception { 
     Thread.currentThread().setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { 
      public void uncaughtException(Thread t, Throwable e) { 
       System.out.println("Handled exception - let's log it!"); 
       // Logging code here 
      } 
     }); 

     System.out.println("Exception testing"); 
     throw new Exception("Catch and log me!"); 
    } 

}

運行javac App.java && java App生產：

Exception testing 
Handled exception - let's log it!

我懷疑要給出的建議是：「你不應該有任何未捕獲的異常」，但我不知道我保證無論如何，對Maven和非Maven結果之間的差異感到好奇。

來源

2015-10-26 Tom Jardine-McNamara

它與'exec：exec'而不是'exec：java'一起使用嗎？我懷疑這與'exec：java'在一個Maven運行的同一虛擬機內運行Java應用程序的事實有關。 – Tunaki

嗯，我沒有嘗試過。剛剛看過'exec：exec'的文檔，看起來我必須自己設置類路徑，這感覺就像使用Maven一樣。我剛剛嘗試使用'exec：exec'，但無法弄清楚如何傳遞正確的配置。我收到「錯誤：無法找到或加載主類com.mycompany.app.App」（插件配置設置爲'的Java com.mycompany.app.App ' –

JavaExecMojo不會分叉新的進程。相反，它在與mojo相同的線程中調用main方法。所以他們必須捕捉主要方法拋出的任何異常，並模擬jvm的行爲。

我認爲這是maven exec插件中的一個錯誤。看看ExecJavaMojo的源代碼。

的JavaExecMojo只使用

Thread.currentThread().getThreadGroup().uncaughtException(Thread.currentThread(), e);

效仿未捕獲的異常行爲。但是這是不正確的，因爲如果沒有爲當前線程註冊未捕獲的異常處理程序，那麼只有JVM調用uncaughtException方法ThreadGroup。請參閱ThreadGroup.uncaughtException(Thread t, Throwable e)的javadoc。

Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception, and the thread does not have a specific Thread.UncaughtExceptionHandler installed.

我猜開發商想要做的是

try { 
    .... 
    // invoke main method 
} catch (Exception e) { 
    Thread currentThread = Thread.currentThread(); 
    Thread.UncaughtExceptionHandler ueh = currentThread.getUncaughtExceptionHandler(); 
    if (ueh == null) { 
    currentThread.getThreadGroup().uncaughtException(currentThread, e); 
    } else { 
    ueh.uncaughtException(currentThread, e); 
    } 
}

這將模仿JVM的行爲。

您可以使用defaultUncaughtExceptionHandler作爲快速修復。

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { 
    public void uncaughtException(Thread t, Throwable e) { 
    System.out.println("Handled exception - let's log it!"); 
    // Logging code here 
    } 
});

編輯

However, using defaultUncaughtExceptionHandler produces the same java.lang.reflect.InvocationTargetException.

你是對的。他們又做了一個詭計他們使用自己的ThreadGroup實現。見IsolatedThreadGroup

class IsolatedThreadGroup extends ThreadGroup { 
    private Throwable uncaughtException; // synchronize access to this 

    public IsolatedThreadGroup(String name){ 
     super(name); 
    } 

    public void uncaughtException(Thread thread, Throwable throwable) { 
     if (throwable instanceof ThreadDeath) { 
      return; // harmless 
     } 
     synchronized (this) { 
      if (uncaughtException == null) { 
       uncaughtException = throwable; // will be reported eventually 
      } 
     } 
     getLog().warn(throwable); 
    } 
}

的uncaughtException的Javadoc強制執行

The uncaughtException method of ThreadGroup does the following:

If this thread group has a parent thread group, the uncaughtException method of that parent is called with the same two arguments.

Otherwise, this method checks to see if there is a default uncaught exception handler installed, and if so, its uncaughtException method is called with the same two arguments.

Otherwise, this method determines if the Throwable argument is an instance of ThreadDeath. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's getName method, and a stack backtrace, using the Throwable's printStackTrace method, is printed to the standard error stream.

所以其執行不兼容的API。這就是爲什麼defaultUncaughtExceptionHandler不起作用。

結論

不要使用JavaExecMojo。改爲使用ExecMojo。例如。

mvn exec:exec -Dexec.executable="java" -Dexec.workingdir="someDir" -Dexec.args="-cp target/classes"

在pom中指定插件屬性，您可以使用佔位符。例如。

<workingdir>${basedir}</workingdir> 
<args>-cp ${project.build.outputDirectory}</args>

來源

2015-10-26 11:32:08

哇，謝謝但是，使用'defaultUncaughtExceptionHandler'會產生相同的'java.lang.reflect.InvocationTargetException'。 –

@TomJenkins你是對的，我深入瞭解了源代碼並更新了我的答案 –

太棒了，謝謝！幸運的是，我的應用程序將在Maven之外（作爲陰影的jar）在生產環境中運行;我可以在dev中使用它。 –

setUncaughtExceptionHandler在Maven項目中不工作

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