Support for Java 8

[thewillyhuman]

Hi @labra,

We are using this library for Map Reduce processing within Apache Spark and would like to execute some tests on AWS EMR. Unfortunately, their environment uses Java 1.8 and claims that this library was compiled with Java 1.11.

Exception: java.lang.UnsupportedClassVersionError: es/weso/shex/parser/ShExDocLexer has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0.

[thewillyhuman]

I think that in #4 the build.sbt file was modified to compile within Java 1.8 version. But 6 months ago in commit ea59afe the line

shex-s/build.sbt

Line 379 in 3ac75b4

// javacOptions ++= Seq("-source", "1.8", "-target", "1.8"),

was commented.

[labra]

OK, let's try to publish all these libraries in Java 1.8...in principle it should be doable.

[thewillyhuman]

The code depending on Java 1.11 is:

shex-s/modules/wikibaserdf/src/main/scala/es/weso/utils/Deref.scala

Lines 43 to 59 in 505489f

	def derefRDFJava(iri: IRI): IO[Resource[IO,RDFAsJenaModel]] = for {
	str <- IO {
	val client = HttpClient.newBuilder().followRedirects(Redirect.ALWAYS).build()
	val request: HttpRequest = HttpRequest.newBuilder()
	.uri(iri.uri)
	.timeout(Duration.ofMinutes(4))
	.header("Accept", "text/turtle").GET.build()
	println(s"Request: ${request}")
	val response = client.send(request, BodyHandlers.ofString)
	// println(s"Body: ${response.body()}\nEND BODY (drefJava)")
	response.body()
	}
	rdf <- RDFAsJenaModel.fromString(str,"TURTLE")
	} yield rdf
	}

[thewillyhuman]

Looks like this was fixed changing previous lines by the following ones:

shex-s/modules/wikibaserdf/src/main/scala/es/weso/utils/Deref.scala

Lines 49 to 75 in a084b71

	def derefRDFJava(iri: IRI): IO[Resource[IO,RDFAsJenaModel]] = for {
	str <- IO {
	// This code is commented because it depends on Java 1.11
	/* val client = HttpClient.newBuilder().followRedirects(Redirect.ALWAYS).build()
	val request: HttpRequest = HttpRequest.newBuilder()
	.uri(iri.uri)
	.timeout(Duration.ofMinutes(4))
	.header("Accept", "text/turtle").GET.build()
	println(s"Request: ${request}")
	val response = client.send(request, BodyHandlers.ofString)
	// println(s"Body: ${response.body()}\nEND BODY (drefJava)")
	response.body() */
	// Java 1.8 code
	val url: URL = iri.uri.toURL
	val conn: HttpURLConnection = url.openConnection().asInstanceOf[HttpURLConnection]
	conn.setRequestMethod("GET")
	conn.setRequestProperty("Accept", "text/turtle")
	conn.setInstanceFollowRedirects(true)
	// I think redirects still are required to be done manually. See: https://mkyong.com/java/java-httpurlconnection-follow-redirect-example/
	conn.setReadTimeout(5000)
	val in = new BufferedReader(new InputStreamReader(conn.getInputStream()))
	val str = in.lines().iterator.asScala.mkString
	conn.connect()
	str
	}
	rdf <- RDFAsJenaModel.fromString(str,"TURTLE")
	} yield rdf

So this issue looks like is fixed.