在jar中访问资源文件夹 [英] Access resource folder within jar

问题描述

我试图在构建JAR之后阅读资源文件夹的内容。资源文件夹在IDE设置（IntelliJ）中标记为 source 。

我尝试了以下方法：

  InputStream input = getClass（）。getResourceAsStream（../ objectLocation.json）; 
 JsonReader jsonReader = new JsonReader（new InputStreamReader（input））; 
  

我也试过：

<$ p $ jsonReader jsonReader = new JsonReader（new FileReader（../ resources / objectLocation.json））;

这两种方法都会导致：

导致：

$ p $ java.io.FileNotFoundException：com / layers / resources / objectLocation.json（没有这样的文件或目录）


文件结构：

  src 
 
 -com.layers  - > myClasses 
 
 -resources  - > JSON 
  

编辑：

  InputStream input = getClass（）。getResourceAsStream（objectLocation.json）; 
 JsonReader jsonReader = new JsonReader（new InputStreamReader（input））; 
  

结果为：

  java.lang.NullPointerException 
  

解决方案

通过 getResourceAsStream（）加载Java中的资源时，不理解绝对和相对路径错误导致 NullPointerException 。

假设以下结构和内容：

 我的项目
 | -src 
 | --main 
 | -java 
 | |  - 一些包
 | | -SomeClass.java 
 | -resources 
 | -Root.txt 
 | -SomePackage 
 | -MyData.txt 
 | -SomePackage2 
 |  - MySubData.txt 
  

内容将在.jar中进行重新组织：

  | -Root.txt 
 | -SomePackage 
 | -SomeClass.java 
 | -MyData.txt 
 | -SomePackage2 
 | -MySubData.txt 
  

什么不检索资源数据：

  InputStream IS; 
 IS = SomeClass.class.getResourceAsStream（Root.txt）; //不行
 
 IS = SomeClass.class.getResourceAsStream（/ Root.txt）; // OK 
 
 IS = SomeClass.class.getResourceAsStream（/ MyData.txt）; //不好
 
 IS = SomeClass.class.getResourceAsStream（MyData.txt）; // OK 
 
 IS = SomeClass.class.getResourceAsStream（/ SomePackage / MyData.txt）; // OK 
 
 IS = SomeClass.class.getResourceAsStream（SomePackage / MyData.txt）; //不好
 
 IS = SomeClass.class.getResourceAsStream（MySubData.txt）; //不正确
 
 IS = SomeClass.class.getResourceAsStream（SomePackage / SomePackage2 / MySubData.txt）; // OK 
 
 IS = SomeClass.class.getResourceAsStream（/ SomePackage / SomePackage2 / MySubData.txt）; //不行
 
 IS = SomeClass.class.getResourceAsStream（/ SomePackage2 / MySubData.txt）; //不好
 
 IS = SomeClass.class.getResourceAsStream（SomePackage2 / MySubData.txt）; // OK 
  

getResourceAsStream（）到与被调用的Class实例对应的包。

I am trying to read the contents of a resource folder once my JAR is built. The resource folder is marked as a source in the IDE settings (IntelliJ).

I have tried the following methods:

  InputStream input = getClass().getResourceAsStream("../objectLocation.json");
  JsonReader jsonReader = new JsonReader(new InputStreamReader(input));

I have also tried:

  JsonReader jsonReader = new JsonReader(new FileReader("../resources/objectLocation.json"));

Both of these methods results in :

Which results in:

java.io.FileNotFoundException: com/layers/resources/objectLocation.json (No such file or directory)

File structure:

src

-com.layers -> myClasses

-resources -> JSON

EDIT:

  InputStream input = getClass().getResourceAsStream("objectLocation.json");
  JsonReader jsonReader = new JsonReader(new InputStreamReader(input));

Results in a:

java.lang.NullPointerException

解决方案

Not understanding the difference between absolute and relative paths when loading resources in Java via getResourceAsStream() is a common source of errors leading to NullPointerException.

Assuming the following structure and content:

My Project
  |-src
    |-main
      |-java
      | |-SomePackage
      |   |-SomeClass.java
      |-resources
        |-Root.txt
        |-SomePackage
          |-MyData.txt
          |-SomePackage2
            |-MySubData.txt

Content will be re-organized as following in the .jar:

|-Root.txt
  |-SomePackage
    |-SomeClass.java
    |-MyData.txt
    |-SomePackage2
      |-MySubData.txt

The following indicates what works and what does not work to retrieve resource data:

InputStream IS;
IS = SomeClass.class.getResourceAsStream("Root.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("/Root.txt"); // OK

IS = SomeClass.class.getResourceAsStream("/MyData.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("MyData.txt"); // OK

IS = SomeClass.class.getResourceAsStream("/SomePackage/MyData.txt"); // OK

IS = SomeClass.class.getResourceAsStream("SomePackage/MyData.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("MySubData.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("SomePackage/SomePackage2/MySubData.txt"); // OK

IS = SomeClass.class.getResourceAsStream("/SomePackage/SomePackage2/MySubData.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("/SomePackage2/MySubData.txt"); // Not OK

IS = SomeClass.class.getResourceAsStream("SomePackage2/MySubData.txt"); // OK

getResourceAsStream() operates relative to the package corresponding to the called Class instance.

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