Java（maven）：如何知道错误的位置（无用的回溯）(Java (maven) : how to know where lies the error (useless backtrace))

 我正在用maven编写我的第一个项目（ 这里 ）。 当我使用mvn -Dtest=EchoTest test运行mvn -Dtest=EchoTest test ，我得到了一个BUILD FAILURE 
 
nonAcceptedTypeVerification(EchoTest)  Time elapsed: 0.044 sec  <<< ERROR!
java.lang.NullPointerException
    at EchoTest.initialize(EchoTest.java:50)
 
 我怎样才能更准确地知道代码中的哪一行触发NullPointerExcepion ？ 换句话说：如何让Maven打印整个回溯？ 
 
 我尝试了mvn -e ，并在target子目录中搜索。 
 
 编辑 
 
 以下是引发NullPointerException的行（在EchoText.java中）： 
 
@Before
public void initialize() throws InterruptedException
{
    system = new EchoActorSystem();
    echo_actor = system.actorOf();  <-- line 50
}
 
 关键是EchoActorSystem是一个非常复杂的类，方法actorOf做了很多工作，从system调用许多函数。 例如，它调用super.actorOf()然后修复结果的某些属性，依此类推。 我通过添加许多Sysytem.out.println搜索错误的行，但我确信这不是正确的工作方式。 

I'm writing my first project with maven (here). When I run the tests with mvn -Dtest=EchoTest test, I get a BUILD FAILURE with
 
nonAcceptedTypeVerification(EchoTest)  Time elapsed: 0.044 sec  <<< ERROR!
java.lang.NullPointerException
    at EchoTest.initialize(EchoTest.java:50)
 
How can I know more precisely what line in my code triggers the NullPointerExcepion ? In other words : how to ask Maven to print the whole backtrace ?
 
I tried mvn -e, and searched in the target subdirectory.
 
EDIT
 
Here are the lines provoking the NullPointerException (in EchoText.java) :
 
@Before
public void initialize() throws InterruptedException
{
    system = new EchoActorSystem();
    echo_actor = system.actorOf();  <-- line 50
}
 
The point is that EchoActorSystem is a quite complex class and the method actorOf makes tons of work, calling many functions from system. For example it calls super.actorOf() and then fix some properties of the result, and so on. I'm searching the faulty line by adding many Sysytem.out.println, but I'm sure that this is not the right way to work.

原文：https://stackoverflow.com/questions/35506936