Spring / Maven load file from classpath

Question

in my resources folder:

src/main/resources

I have two files the application.properties file and a JSON file app.schema.json

I have the following function:

private File loadSchema(String schemaName) throws JsonSchemaMissingException { ClassLoader classLoader = JsonSchemaValidator.class.getClassLoader(); File file = new File(Objects.requireNonNull(classLoader.getResource("app.schema.json")).getFile()); if (!file.exists()) { log.LogErrorWithTransactionId("", "file does not exist " + file.getAbsolutePath()); throw new JsonSchemaMissingException("file does not exist"); } return file; }

If I run mvn spring-boot:run it successfully find the file. If I run:

mvn package
java -jar app.jar

I get a NullPointer because the following file does not exist:

/home/XXX/Docs/project/XXX/file:/home/ghovat/Docs/project/XXX/target/app.jar!/BOOT-INF/classes!/app.event.json

In my pom.xml in build I added with and without the following setting:

<resources> <resource> <directory>src/main/resources</directory> </resource> </resources>

Neither way it works. It can reach the file if I run mvn spring-boot:run but also if I run mvn clean package spring-boot:repackage and java -jar target/app.jar It doesnt find the file.

I checked all the docs and tried several different ways to load the file but either way it doesnt find it.

How can I make the file available?

The problem here is that your app.event.json is not accessible as a file, as it is inside the app.jar file. You must access it as a resource. Your code doesn't show wht happens with the result of loadSchema, but it should be able to handle InputStream. As long as you stick to InputStream you should be good. — Robert Scholte
– Robert Scholte, Commented Nov 3, 2019 at 13:48

VadymVL · Accepted Answer · 2019-11-01 15:36:52Z

1

You need to include your src/main/resources directory to the classpath in your pom.xml using its relative path:

 <build> <resources> <resource> <directory>src/main/resources</directory> </resource> </resources> </build>

You can read more about it here.

answered Nov 1, 2019 at 15:36

VadymVL

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1 Comment

ghovat Over a year ago

thanks for your answer. I tried it with the absolute path as well I receive the same error.

file does not exist /home/XXX/Dokumente/project/XXX/file:/home/XXX/Dokumente/project/XXX/target/app.jar!/BOOT-INF/classes!/app.event.json

Ashok Prajapati · Accepted Answer · 2019-11-01 18:15:51Z

Can you please check inside jar if it contains the mentioned file in classes folder. Also you can try below code to load the file from classpath.

Thread.currentThread().getContextClassLoader().getResource(<file_name>)

If possible then keep that file outside the jar in some folder location and set that location as classpath when executing the jar.

Thanks for your answer. If i run mvn spring-boot:run the file exists inside of the jar. If I just run mvn package and java -jar XXX.jar it doesnt exist: /home/XXX/Dokumente/project/XXX/target/classes/XXX.json if I unpack the jaar maually I see the file in BOOT-INF/classes/

ghovat · Accepted Answer · 2019-11-04 09:22:58Z

As Ropert Scholte mentioned to fix it I used Inputstream to load instead of loading it as File. With the Code below I fixed it:

private Reader loadSchema(String schemaName) throws JsonSchemaMissingException { ClassLoader classLoader = JsonSchemaValidator.class.getClassLoader(); InputStream fileStream = classLoader.getResourceAsStream(schemaName); if (fileStream == null) { log.LogErrorWithTransactionId("", "file does not exist "); throw new JsonSchemaMissingException("file does not exist"); } Reader reader = new InputStreamReader(fileStream, StandardCharsets.UTF_8); return reader; }

Note since I use the file for validating a JSON Schema I needed to convert the Inputstream to a reader object

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