Java Library: load file from resources

Question

I'm a developing a Java library that is going to be used internally in our company. It provides a wrapper around Aerospike. When a user calls the factory method, the library should read a file from its resources.

public static IAerospikeClient newTypedClient(IAerospikeClient client) {
    LOG.info("Trying to load aerospike schema yml");

    URL resource = AerospikeTypedClientFactory.class.getClassLoader().getResource("schema.yml");
    if (resource == null) {
        throw new IllegalArgumentException("File 'schema.yml' is not found");
    }

    byte[] bytes = Files.readAllBytes(Paths.get(resource.toURI()));
    return new TypedAerospikeClient(client, new String(bytes));
}

Then I'm trying to add this library as a dependency and call newTypedClient method, I get this error.

Caused by: java.nio.file.FileSystemNotFoundException
    at com.sun.nio.zipfs.ZipFileSystemProvider.getFileSystem(ZipFileSystemProvider.java:171)
    at com.sun.nio.zipfs.ZipFileSystemProvider.getPath(ZipFileSystemProvider.java:157)
    at java.nio.file.Paths.get(Paths.java:143)
    at com.example.AerospikeTypedClientFactory.newTypedClient(AerospikeTypedClientFactory.java:30)

Is there any way to overcome this error? I guess I could add the schema.yml file to the resources folder of the library's consumer. But I definitely don't want to go into this. Because the purpose is to get rid of configurations and put them within a single artefact.

EDIT 1

For those who refer to How should I use getResource() in Java? question. I do understand that getResource reads from the classpath. My question is how can I get this work? Perhaps, I can replace getResource/getResourceAsStream usage with something else. The idea is that schema.yml has to be packed within the library .jar archive.

EDIT 2

Here is the problem step by step.

The described code is put within the lib module.
The lib is packed to jar and published to Artifactory.
The service put a dependency on lib.
The service calls the newTypedClient method from the lib.
The FileSystemNotFoundException raises.

So, I need lib to read schema.yml from the jar it is packed to. Is it possible? Here is the diagram that describes the process.

Does this answer your question? [How should I use getResource() in Java?](https://stackoverflow.com/questions/6400646/how-should-i-use-getresource-in-java) — pringi, Feb 28 '22 at 13:59
@pringi No, it does not. I updated the question with explanations — Semyon Kirekov, Feb 28 '22 at 14:13
So, if I understand your question correctly... once you built your JAR file, if you open it with an archive tool (e.g. 7-Zip), then you don't find ```schema.yml``` present? — majixin, Feb 28 '22 at 14:28
@pringi No, there is a different kind of problem. Suppose there is a `service` and the `lib` with the code above. I put `lib` as a dependency in `build.gradle` of `service`. When I call `newTypedClient` method inside the `service` code, I get the described exception. So, I want the `lib` to read `schema.yml` from its `resources` folder. It does work when I test `lib` in isolation. But it stops working when I include `lib` as a dependency. — Semyon Kirekov, Feb 28 '22 at 18:59

score 0 · Accepted Answer · answered Mar 05 '22 at 16:01

For those who interested, I wrote a custom Gradle task that generates a class with the static String field. This field value equals to the actual file content. The task runs before compileJava one. For the generation itself I use JavaPoet library. Here is the example.

task generateSchemaClass {
    def className = "Schema_"
    def directoryPath = "src/main/java/com/example/generated"
    def filePath = directoryPath + className + ".java"
    doFirst {
        TypeSpec typeSpec = TypeSpec.classBuilder("Schema_")
                .addModifiers(Modifier.PUBLIC)
                .addAnnotation(
                        AnnotationSpec.builder(SuppressWarnings.class)
                                .addMember("value", '$S', "all")
                                .build()
                )
                .addField(
                        FieldSpec.builder(String.class, "CONTENT", Modifier.PUBLIC, Modifier.STATIC, Modifier.FINAL)
                                .initializer('$S', file('src/main/resources/schema.yml').text)
                                .build()
                )
                .build()
        JavaFile javaFile = JavaFile.builder("com.example.generated", typeSpec).build()
        file(directoryPath).mkdirs()

        def output = file(filePath)
        output.createNewFile()
        output.text = javaFile.toString()
    }
}

compileJava.dependsOn(generateSchemaClass)

Java Library: load file from resources

EDIT 1

EDIT 2

1 Answers1