How to really read text file from classpath in Java

Question

I am trying to read a text file which is set in CLASSPATH system variable  Not a user variable   I am trying to get input stream to the file as below   Place the directory of file  D  myDir in CLASSPATH and try below   InputStream in   this getClass   getClassLoader   getResourceAsStream  SomeTextFile txt    InputStream in   this getClass   getClassLoader   getResourceAsStream   SomeTextFile txt    InputStream in   this getClass   getClassLoader   getResourceAsStream    SomeTextFile txt      Place full path of file  D  myDir SomeTextFile txt in CLASSPATH and try the same above 3 lines of code   But unfortunately NONE of them are working and I am always getting null into my InputStream in

User · Answer

Don t use getClassLoader   method and use the     before the file name      is very important  this getClass   getResourceAsStream   SomeTextFile txt

User · Answer

To actually read the contents of the file  I like using Commons IO   Spring Core  Assuming Java 8   try  InputStream stream   new ClassPathResource  package resource   getInputStream          IOUtils toString stream       Alternatively   InputStream stream   null  try       stream   new ClassPathResource   log4j xml   getInputStream        IOUtils toString stream     finally       IOUtils closeQuietly stream

User · Answer

Use org apache commons io FileUtils readFileToString new File  src test resources sample-data fileName txt

User · Answer

you have to put your  system variable  on the java classpath

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To get the class absolute path try this   String url   this getClass   getResource     getPath

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To read the contents of a file into a String from the classpath  you can use this   private String resourceToString String filePath  throws IOException  URISyntaxException       try  InputStream inputStream   this getClass   getClassLoader   getResourceAsStream filePath                 return IOUtils toString inputStream             Note  IOUtils is part of Commons IO   Call it like this   String fileContents   resourceToString  ImOnTheClasspath txt

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When using the Spring Framework  either as a collection of utilities or container - you do not need to use the latter functionality  you can easily use the Resource abstraction   Resource resource   new ClassPathResource  com example Foo class      Through the Resource interface you can access the resource as InputStream  URL  URI or File  Changing the resource type to e g  a file system resource is a simple matter of changing the instance

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If you use Guava  import com google common io Resources   we can get URL from CLASSPATH  URL resource   Resources getResource  quot test txt quot    String file   resource getFile         get file path   or InputStream  InputStream is   Resources getResource  quot test txt quot   openStream     Ways to convert an InputStream to a String

User · Answer

You say  I am trying to read a text file which is set in CLASSPATH system variable   My guess this is on Windows and you are using this ugly dialog to edit the  System Variables    Now you run your Java program in the console  And that doesn t work  The console gets a copy of the values of the system variables once when it is started  This means any change in the dialog afterwards doesn t have any effect   There are these solutions    Start a new console after every change Use set CLASSPATH     in the console to set the copy of the variable in the console and when your code works  paste the last value into the variable dialog  Put the call to Java into  BAT file and double click it  This will create a new console every time  thus copying the current value of the system variable     BEWARE  If you also have a User variable CLASSPATH then it will shadow your system variable  That is why it is usually better to put the call to your Java program into a  BAT file and set the classpath in there  using set CLASSPATH   rather than relying on a global system or user variable   This also makes sure that you can have more than one Java program working on your computer because they are bound to have different classpaths

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Scenario    1  client-service-1 0-SNAPSHOT jar has dependency read-classpath-resource-1 0-SNAPSHOT jar   2  we want to read content of class path resources  sample txt  of read-classpath-resource-1 0-SNAPSHOT jar through client-service-1 0-SNAPSHOT jar   3  read-classpath-resource-1 0-SNAPSHOT jar has src main resources sample txt          Here is working sample code I prepared  after 2-3days wasting my development time  I found the complete end-to-end solution  hope this helps to save your time      1 pom xml of read-classpath-resource-1 0-SNAPSHOT jar   lt  xml version  1 0  encoding  UTF-8   gt           lt project xmlns  http   maven apache org POM 4 0 0  xmlns xsi  http   www w3 org 2001 XMLSchema-instance  xsi schemaLocation  http   maven apache org POM 4 0 0 http   maven apache org xsd maven-4 0 0 xsd  gt               lt modelVersion gt 4 0 0 lt  modelVersion gt               lt groupId gt jar-classpath-resource lt  groupId gt               lt artifactId gt read-classpath-resource lt  artifactId gt               lt version gt 1 0-SNAPSHOT lt  version gt               lt name gt classpath-test lt  name gt               lt properties gt                   lt project build sourceEncoding gt UTF-8 lt  project build sourceEncoding gt                   lt org springframework version gt 4 3 3 RELEASE lt  org springframework version gt                   lt mvn release plugin gt 2 5 1 lt  mvn release plugin gt                   lt output path gt   project artifactId  lt  output path gt                   lt io dropwizard version gt 1 0 3 lt  io dropwizard version gt                   lt commons-io verion gt 2 4 lt  commons-io verion gt               lt  properties gt               lt dependencies gt                   lt dependency gt                       lt groupId gt org springframework lt  groupId gt                       lt artifactId gt spring-core lt  artifactId gt                       lt version gt   org springframework version  lt  version gt                   lt  dependency gt                   lt dependency gt                       lt groupId gt org springframework lt  groupId gt                       lt artifactId gt spring-context lt  artifactId gt                       lt version gt   org springframework version  lt  version gt                   lt  dependency gt                   lt dependency gt                       lt groupId gt commons-io lt  groupId gt                       lt artifactId gt commons-io lt  artifactId gt                       lt version gt   commons-io verion  lt  version gt                   lt  dependency gt               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  resources gt                   lt plugins gt                       lt plugin gt                           lt groupId gt org apache maven plugins lt  groupId gt                           lt artifactId gt maven-release-plugin lt  artifactId gt                           lt version gt   mvn release plugin  lt  version gt                       lt  plugin gt                       lt plugin gt                           lt groupId gt org apache maven plugins lt  groupId gt                           lt artifactId gt maven-compiler-plugin lt  artifactId gt                           lt version gt 3 1 lt  version gt                           lt configuration gt                               lt source gt 1 8 lt  source gt                               lt target gt 1 8 lt  target gt                               lt encoding gt UTF-8 lt  encoding gt                           lt  configuration gt                       lt  plugin gt                       lt plugin gt                           lt artifactId gt maven-jar-plugin lt  artifactId gt                           lt version gt 2 5 lt  version gt                           lt configuration gt                               lt outputDirectory gt   project build directory  lib lt  outputDirectory gt                               lt archive gt                                   lt manifest gt                                       lt addClasspath gt true lt  addClasspath gt                                       lt useUniqueVersions gt false lt  useUniqueVersions gt                                       lt addDefaultImplementationEntries gt true lt  addDefaultImplementationEntries gt                                       lt mainClass gt demo read classpath resources ClassPathResourceReadTest lt  mainClass gt                                   lt  manifest gt                                   lt manifestEntries gt                                       lt Implementation-Artifact-Id gt   project artifactId  lt  Implementation-Artifact-Id gt                                       lt Class-Path gt sample txt lt  Class-Path gt                                   lt  manifestEntries gt                               lt  archive gt                           lt  configuration gt                       lt  plugin gt                       lt plugin gt                           lt groupId gt org apache maven plugins lt  groupId gt                           lt artifactId gt maven-shade-plugin lt  artifactId gt                           lt version gt 2 2 lt  version gt                           lt configuration gt                               lt createDependencyReducedPom gt false lt  createDependencyReducedPom gt                               lt filters gt                                   lt filter gt                                       lt artifact gt     lt  artifact gt                                       lt excludes gt                                           lt exclude gt META-INF   SF lt  exclude gt                                           lt exclude gt META-INF   DSA lt  exclude gt                                           lt exclude gt META-INF   RSA lt  exclude gt                                       lt  excludes gt                                   lt  filter gt                               lt  filters gt                           lt  configuration gt                           lt executions gt                               lt execution gt                                   lt phase gt package lt  phase gt                                   lt goals gt                                       lt goal gt shade lt  goal gt                                   lt  goals gt                                   lt configuration gt                                       lt transformers gt                                           lt transformer implementation  org apache maven plugins shade resource ServicesResourceTransformer    gt                                           lt transformer implementation  org apache maven plugins shade resource ManifestResourceTransformer  gt                                               lt mainClass gt demo read classpath resources ClassPathResourceReadTest lt  mainClass gt                                           lt  transformer gt                                       lt  transformers gt                                   lt  configuration gt                               lt  execution gt                           lt  executions gt                       lt  plugin gt                   lt  plugins gt               lt  build gt           lt  project gt    2 ClassPathResourceReadTest java class in read-classpath-resource-1 0-SNAPSHOT jar that loads the class path resources file content   package demo read classpath resources   import java io BufferedReader  import java io IOException  import java io InputStream  import java io InputStreamReader  import java util ArrayList  import java util List   public final class ClassPathResourceReadTest       public ClassPathResourceReadTest   throws IOException           InputStream inputStream   getClass   getResourceAsStream   sample txt            BufferedReader reader   new BufferedReader new InputStreamReader inputStream            List lt Object gt  list   new ArrayList lt  gt             String line          while   line   reader readLine       null                list add line                     for  Object s1  list                System out println         s1                     System out println  getClass   getResourceAsStream   sample txt   lines    list size               3 pom xml of client-service-1 0-SNAPSHOT jar   lt  xml version  1 0  encoding  UTF-8   gt   lt project xmlns  http   maven apache org POM 4 0 0           xmlns xsi  http   www w3 org 2001 XMLSchema-instance           xsi schemaLocation  http   maven apache org POM 4 0 0 http   maven apache org xsd maven-4 0 0 xsd  gt       lt modelVersion gt 4 0 0 lt  modelVersion gt        lt groupId gt client-service lt  groupId gt       lt artifactId gt client-service lt  artifactId gt       lt version gt 1 0-SNAPSHOT lt  version gt        lt dependencies gt           lt dependency gt               lt groupId gt jar-classpath-resource lt  groupId gt               lt artifactId gt read-classpath-resource lt  artifactId gt               lt version gt 1 0-SNAPSHOT lt  version gt           lt  dependency gt       lt  dependencies gt        lt build gt           lt plugins gt               lt plugin gt                   lt artifactId gt maven-jar-plugin lt  artifactId gt                   lt version gt 2 5 lt  version gt                   lt configuration gt                       lt outputDirectory gt   project build directory  lib lt  outputDirectory gt                       lt archive gt                           lt manifest gt                               lt addClasspath gt true lt  addClasspath gt                               lt useUniqueVersions gt false lt  useUniqueVersions gt                               lt addDefaultImplementationEntries gt true lt  addDefaultImplementationEntries gt                               lt mainClass gt com crazy issue client AccessClassPathResource lt  mainClass gt                           lt  manifest gt                           lt manifestEntries gt                               lt Implementation-Artifact-Id gt   project artifactId  lt  Implementation-Artifact-Id gt                               lt Implementation-Source-SHA gt   buildNumber  lt  Implementation-Source-SHA gt                               lt Class-Path gt sample txt lt  Class-Path gt                           lt  manifestEntries gt                       lt  archive gt                   lt  configuration gt               lt  plugin gt               lt plugin gt                   lt groupId gt org apache maven plugins lt  groupId gt                   lt artifactId gt maven-shade-plugin lt  artifactId gt                   lt version gt 2 2 lt  version gt                   lt configuration gt                       lt createDependencyReducedPom gt false lt  createDependencyReducedPom gt                       lt filters gt                           lt filter gt                               lt artifact gt     lt  artifact gt                               lt excludes gt                                   lt exclude gt META-INF   SF lt  exclude gt                                   lt exclude gt META-INF   DSA lt  exclude gt                                   lt exclude gt META-INF   RSA lt  exclude gt                               lt  excludes gt                           lt  filter gt                       lt  filters gt                   lt  configuration gt                   lt executions gt                       lt execution gt                           lt phase gt package lt  phase gt                           lt goals gt                               lt goal gt shade lt  goal gt                           lt  goals gt                           lt configuration gt                               lt transformers gt                                   lt transformer implementation  org apache maven plugins shade resource ServicesResourceTransformer    gt                                   lt transformer implementation  org apache maven plugins shade resource ManifestResourceTransformer  gt                                       lt mainClass gt com crazy issue client AccessClassPathResource lt  mainClass gt                                   lt  transformer gt                               lt  transformers gt                           lt  configuration gt                       lt  execution gt                   lt  executions gt               lt  plugin gt           lt  plugins gt       lt  build gt   lt  project gt    4 AccessClassPathResource java instantiate ClassPathResourceReadTest java class where  it is going to load sample txt and prints its content also   package com crazy issue client   import demo read classpath resources ClassPathResourceReadTest  import java io IOException   public class AccessClassPathResource       public static void main String   args  throws IOException           ClassPathResourceReadTest test   new ClassPathResourceReadTest              5 Run Executable jar as follows    ravibeli localhost lib   java -jar client-service-1 0-SNAPSHOT jar                                          I am in resources directory of read-classpath-resource-1 0-SNAPSHOT jar                                          3  getClass   getResourceAsStream   sample txt    3

User · Answer

Please try  InputStream in   this getClass   getResourceAsStream   SomeTextFile txt      Your tries didn t work because only the class loader for your classes is able to load from the classpath  You used the class loader for the java system itself

User · Answer

With the directory on the classpath  from a class loaded by the same classloader  you should be able to use either of      From ClassLoader  all paths are  absolute  already - there s no context    from which they could be relative  Therefore you don t need a leading slash  InputStream in   this getClass   getClassLoader                                    getResourceAsStream  SomeTextFile txt       From Class  the path is relative to the package of the class unless    you include a leading slash  so if you don t want to use the current    package  include a slash like this  InputStream in   this getClass   getResourceAsStream   SomeTextFile txt      If those aren t working  that suggests something else is wrong   So for example  take this code   package dummy   import java io     public class Test       public static void main String   args                InputStream stream   Test class getResourceAsStream   SomeTextFile txt            System out println stream    null           stream   Test class getClassLoader   getResourceAsStream  SomeTextFile txt            System out println stream    null             And this directory structure   code     dummy           Test class txt     SomeTextFile txt   And then  using the Unix path separator as I m on a Linux box    java -classpath code txt dummy Test   Results   true true

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Somehow the best answer doesn t work for me  I need to use a slightly different code instead   ClassLoader loader   Thread currentThread   getContextClassLoader    InputStream is   loader getResourceAsStream  SomeTextFile txt      I hope this help those who encounters the same issue

User · Answer

If you compile your project in jar file   you can put your file in resources files your file text or pdf   and use this code    import org slf4j Logger  import org slf4j LoggerFactory  import java io     public class readFileService        private static final Logger LOGGER   LoggerFactory getLogger readFileService class         public byte   getFile            String filePath   files your file           InputStream inputStreamFile          byte   bytes          try              inputStreamFile   this getClass   getResourceAsStream filePath               bytes   new byte inputStreamFile available                 inputStreamFile read bytes                 catch NullPointerException   IOException e                LOGGER error  Erreur read file   filePath   error message     e getMessage                 return null                    return bytes

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I am  using webshpere application server and my Web Module is build on Spring MVC  The Test properties were located in the resources folder  i tried to load this files using the following    this getClass   getClassLoader   getResourceAsStream  Test properties      this getClass   getResourceAsStream   Test properties      None of the above code loaded the file   But with the help of below code the property file was loaded successfully   Thread currentThread   getContextClassLoader   getResourceAsStream  Test properties     Thanks to the user  user1695166

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import java io BufferedReader  import java io File  import java io FileNotFoundException  import java io FileReader  import java io IOException   public class ReadFile                     feel free to make any modification I have have been here so I feel you             param args    throws InterruptedException              public static void main String   args  throws InterruptedException              thread pool of 10         File dir   new File                  read file from same directory as source            if  dir isDirectory                  File   files   dir listFiles                for  File file   files                       if you wanna read file name with txt files                 if  file getName   contains  txt                          System out println file getName                                           if you want to open text file and read each line then                 if  file getName   contains  txt                          try                              FileReader reads text files in the default encoding                          FileReader fileReader   new FileReader                                  file getAbsolutePath                                Always wrap FileReader in BufferedReader                          BufferedReader bufferedReader   new BufferedReader                                  fileReader                           String line                             get file details and get info you need                          while   line   bufferedReader readLine       null                                System out println line                                  here you can say                                   System out println line substring 0  10    this                                prints from 0 to 10 indext                                                 catch  FileNotFoundException ex                            System out println  Unable to open file                                      file getName                                 catch  IOException ex                            System out println  Error reading file                                      file getName                                      Or we could just do this                          ex printStackTrace

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This is how I read all lines of a text file on my classpath  using Java 7 NIO       import java nio charset Charset  import java nio file Files  import java nio file Paths        Files readAllLines      Paths get this getClass   getResource  res txt   toURI     Charset defaultCharset       NB this is an example of how it can be done  You ll have to make improvements as necessary  This example will only work if the file is actually present on your classpath  otherwise a NullPointerException will be thrown when getResource   returns null and  toURI   is invoked on it   Also  since Java 7  one convenient way of specifying character sets is to use the constants defined in java nio charset StandardCharsets  these are  according to their javadocs   guaranteed to be available on every implementation of the Java platform      Hence  if you know the encoding of the file to be UTF-8  then specify explicitly the charset StandardCharsets UTF 8

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My answer is not exactly what is asked in the question  Rather I am giving a solution exactly how easily we can read a file into out java application from our project class path   For example suppose a config file name example xml is located in a path like below -  com myproject config dev  and our java executable class file is in the below path -  com myproject server main  now just check in both the above path which is the nearest common directory folder from where you can access both dev and main directory folder  com myproject server main - where our application   s java executable class is existed       We can see that it is myproject folder directory which is the nearest common directory folder from where we can access our example xml file  Therefore from a java executable class resides in  folder directory main we have to go back two steps like        to access myproject  Now following this  see how we can read the file -  package com myproject server main   class Example      File xmlFile     public Example           String filePath   this getClass   getResource        config dev example xml   getPath           this xmlFile   new File filePath            public File getXMLFile           return this xmlFile         public static void main String args           Example ex   new Example          File xmlFile   ex getXMLFile

[java] How to really read text file from classpath in Java

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