getResourceAsStream returns null

Question

I m loading a text file from within a package in a compiled JAR of my Java project  The relevant directory structure is as follows    src initialization Lifepaths txt   My code loads a file by calling Class  getResourceAsStream to return a InputStream    public class Lifepaths       public static void execute             System out println Lifepaths class getClass                getResourceAsStream   initialization Lifepaths txt                private Lifepaths             This is temporary  will eventually be called from outside     public static void main String   args   execute         The print out will always print null  no matter what I use  I m not sure why the above wouldn t work  so I ve also tried      src initialization Lifepaths txt   initialization Lifepaths txt   Lifepaths txt    Neither of these work  I ve read numerous questions so far on the topic  but none of them have been helpful - usually  they just say to load files using the root path  which I m already doing  That  or just load the file from the current directory  just load filename   which I ve also tried  The file is being compiled into the JAR in the appropriate location with the appropriate name    How do I solve this

User · Answer

So there are several ways to get a resource from a jar and each has slightly different syntax where the path needs to be specified differently.

The best explanation I have seen is this article from InfoWorld. I'll summarize here, but if you want to know more you should check out the article.

Methods

ClassLoader.getResourceAsStream().

Format: "/"-separated names; no leading "/" (all names are absolute).

Example: this.getClass().getClassLoader().getResourceAsStream("some/pkg/resource.properties");

Class.getResourceAsStream()

Format: "/"-separated names; leading "/" indicates absolute names; all other names are relative to the class's package

Example: this.getClass().getResourceAsStream("/some/pkg/resource.properties");

Updated Sep 2020: Changed article link. Original article was from Javaworld, it is now hosted on InfoWorld (and has many more ads)

User · Answer

I found myself in a similar issue  Since I am using maven I needed to update my pom xml to include something like this           lt  dependencies gt   lt build gt       lt resources gt           lt resource gt               lt directory gt  src main resources lt  directory gt           lt  resource gt           lt resource gt               lt directory gt    src main resources lt  directory gt           lt  resource gt       lt  resources gt       lt pluginManagement gt                Note the resource tag in there to specify where that folder is  If you have nested projects  like I do  then you might want to get resources from other areas instead of just in the module you are working in  This helps reduce keeping the same file in each repo if you are using similar config data

User · Answer

There seems to be issue with the ClassLoader that you are using  Use the contextClassLoader to load class   This is irrespective of whether it is in a static non-static method  Thread currentThread   getContextClassLoader   getResourceAsStream

User · Answer

What worked for me was to add the file under My Project Java Resources src and then use   this getClass   getClassLoader   getResourceAsStream  myfile txt      I didn t need to explicitly add this file to the path  adding it to  src does that apparently

User · Answer

if you are using Maven make sure your packing is  jar  not  pom      lt packaging gt jar lt  packaging gt

User · Answer

Don t use absolute paths  make them relative to the  resources  directory in your project  Quick and dirty code that displays the contents of MyTest txt from the directory  resources     Test public void testDefaultResource            can we see default resources     BufferedInputStream result    BufferedInputStream            Config class getClassLoader   getResourceAsStream  MyTest txt        byte    b   new byte 256       int val   0      String txt   null      do           try               val   result read b               if  val  gt  0                    txt    new String b  0  val                           catch  IOException e                e printStackTrace                     while  val  gt  -1       System out println txt

User · Answer

What worked for me is I placed the file under src main java myfile log  and InputStream is   getClass   getClassLoader   getResourceAsStream  quot myfile log quot                     if  is    null                throw new FileNotFoundException  quot Log file not provided quot

User · Answer

What you really need is a full absolute classPath for the file  So instead of guessing it  try to find out the ROOT and then move the file to a better location base one  lt  war  file structures     URL test1   getClass   getResource       URL test2   getClass   getClassLoader   getResource                   URL test3   getClass   getClassLoader   getResource          logger info test1 getPath      logger info test2 getPath     logger info test3 getPath

User · Answer

The rules are as follows    check the location of the file you want to load inside the JAR  and thus also make sure it actually added to the JAR  use either an absolute path  path starts at the root of the JAR use an relative path  path starts at the package directory of the class you re calling getResource  getResoucreAsStream   And try   Lifepaths class getResourceAsStream   initialization Lifepaths txt     instead of  Lifepaths class getClass   getResourceAsStream   initialization Lifepaths txt      not sure if it makes a difference  but the former will use the correct ClassLoader  JAR  while I m not sure with the latter

User · Answer

Don t know if of help  but in my case I had my resource in the  src  folder and was getting this error  I then moved the picture to the bin folder and it fixed the issue

User · Answer

Please remove        src main resources  or include file you are trying to read

User · Answer

Make sure your resource directory  e g   src   is in your classpath  make sure it s a source directory in your build path in eclipse    Make sure clazz is loaded from the main classloader   Then  to load src initialization Lifepaths txt  use   clazz getResourceAsStream   initialization Lifepaths txt      Why  clazz getResourcesAsStream foo  looks up foo from within the classpath of clazz  relative to the directory clazz lives in  The leading     makes it load from the root of any directory in the classpath of clazz   Unless you re in a container of some kind  like Tomcat  or are doing something with ClassLoaders directly  you can just treat your eclipse command line classpath as the only classloader classpath

User · Answer

You might want to try this to get the stream i e first get the url and then open it as stream    URL url   getClass   getResource   initialization Lifepaths txt     InputStream strm   url openStream       I once had a similar question  Reading txt file from jar fails but reading image works

User · Answer

The default JVM classloader will use parent-classloader to load resources first      Lifepaths class getClass   s classloader is bootstrap classloader  so getResourceAsStream will search  JAVA HOME only  regardless of user provided classpath  Obviously  Lifepaths txt is not there   Lifepaths class  s classloader is system classpath classloader   so getResourceAsStream will search user-defined classpath and Lifepaths txt is there   When using java lang Class getResourceAsStream String name   name which is not start with     will be added with package name as prefix   If you want avoid this  please using java lang ClassLoader getResourceAsStream   For example   ClassLoader loader   Thread currentThread   getContextClassLoader    String resourceName    Lifepaths txt   InputStream resourceStream   loader getResourceAsStream resourceName

User · Answer

Lifepaths class getClass   getResourceAsStream      loads resources using system class loader  it obviously fails because it does not see your JARs  Lifepaths class getResourceAsStream      loads resources using the same class loader that loaded Lifepaths class and it should have access to resources in your JARs

User · Answer

Emracool    I d suggest you an alternative  Since you seem to be trying to load a   txt file  Better to use FileInputStream   rather then this annoying getClass   getClassLoader   getResourceAsStream   or getClass   getResourceAsStream    At least your code will execute properly

User · Answer

In pom xml manage or remove     src main resources

User · Answer

Roughly speaking   getClass   getResource         Thread currentThread   getContextClassLoader   getResource       Suppose your project structure is like the following    -- src         -- main         -- test       -- test           -- java                  -- com                      -- github                          -- xyz                              -- proj                                  -- MainTest java                                  -- TestBase java           -- resources               -- abcd txt  -- target      -- test-classes          -- com          -- abcd txt       in MainClass java this getClass getResource      - gt     proj dir target test-classes   this getClass getResource      - gt     proj dir target test-classes com github xyz proj   Thread currentThread   getContextClassLoader   getResources      - gt     proj dir target test-classes   Thread currentThread   getContextClassLoader   getResources      - gt   null

[java] getResourceAsStream returns null

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