getClass（）。getResource（“/”）在命令行中返回null

Question

I'm trying to read a file in my maven project at /src/main/resources/file.txt.

I'm using

URL url=this.getClass().getResource("/");
String filePath=url.getPath()+"file.txt";

url object gets the correct value when this is run thru eclipse.

But, when I package the jar and run it in command line:

jar -cp myjar.jar SampleTest

It returns null for 'url' object and throws a NullPointerException in the next line.

I have openend my Jar file using file browser and checked. It has the 'file.txt' in "/" location inside the Jar.

Where am I going wrong ?

Answer 1

There are (often) no directories inside jar files. Therefor it will return null .

---

If you want to get the file you could get that resource directly:

URL fileUrl = getClass().getResource("/file.txt");
...

Or simply:

InputStream fileInputStream = getClass().getResourceAsStream("/file.txt");

Answer 2

您应该将该文件移动到CLASSPATH中，并按以下方式获取：

InputStream is = this.getClass().getResourceAsStream("file.txt");