Java env alpha (#656)

This change adds support for JVM based environment for running Java functions. This is alpha release of JVM environment and might undergo changes.

environments/jvm/src/main/java/io/fission/FunctionLoadRequest.java

@@ -0,0 +1,32 @@
+package io.fission;
+
+public class FunctionLoadRequest {
+
+	private String filepath;
+	private String functionName;
+	private String url;
+
+	String getFilepath() {
+		return filepath;
+	}
+
+	void setFilepath(String filepath) {
+		this.filepath = filepath;
+	}
+
+	String getUrl() {
+		return url;
+	}
+
+	void setUrl(String url) {
+		this.url = url;
+	}
+
+	public String getFunctionName() {
+		return functionName;
+	}
+
+	public void setFunctionName(String functionName) {
+		this.functionName = functionName;
+	}
+}

environments/jvm/src/main/java/io/fission/Server.java

@@ -0,0 +1,123 @@
+package io.fission;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Enumeration;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import org.springframework.boot.*;
+import org.springframework.boot.autoconfigure.*;
+import org.springframework.http.RequestEntity;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import io.fission.Function;
+
+@RestController
+@EnableAutoConfiguration
+public class Server {
+
+	private Function fn;
+
+	private static final int CLASS_LENGTH = 6;
+
+	private static Logger logger = Logger.getGlobal();
+
+	@RequestMapping(value = "/", method = { RequestMethod.GET, RequestMethod.POST, RequestMethod.DELETE,
+			RequestMethod.PUT })
+	ResponseEntity<Object> home(RequestEntity<?> req) {
+		if (fn == null) {
+			return ResponseEntity.badRequest().body("Container not specialized");
+		} else {
+			return ((ResponseEntity<Object>) ((Function) fn).call(req, null));
+		}
+	}
+
+	@PostMapping(path = "/v2/specialize", consumes = "application/json")
+	ResponseEntity<String> specialize(@RequestBody FunctionLoadRequest req) {
+		long startTime = System.nanoTime();
+		File file = new File(req.getFilepath());
+		if (!file.exists()) {
+			return ResponseEntity.badRequest().body("/userfunc/user not found");
+		}
+
+		String entryPoint = req.getFunctionName();
+		logger.log(Level.INFO, "Entrypoint class:" + entryPoint);
+		if (entryPoint == null) {
+			return ResponseEntity.badRequest().body("Entrypoint class is missing in the function");
+		}
+
+		JarFile jarFile = null;
+		ClassLoader cl = null;
+		try {
+
+			jarFile = new JarFile(file);
+			Enumeration<JarEntry> e = jarFile.entries();
+			URL[] urls = { new URL("jar:file:" + file + "!/") };
+
+			// TODO Check if the classloading can be improved for ex. use something like:
+			// Thread.currentThread().setContextClassLoader(cl);
+			if (this.getClass().getClassLoader() == null) {
+				cl = URLClassLoader.newInstance(urls);
+			} else {
+				cl = URLClassLoader.newInstance(urls, this.getClass().getClassLoader());
+			}
+
+			if (cl == null) {
+				return ResponseEntity.status(500).body("Failed to initialize the classloader");
+			}
+
+			// Load all dependent classes from libraries etc.
+			while (e.hasMoreElements()) {
+				JarEntry je = e.nextElement();
+				if (je.isDirectory() || !je.getName().endsWith(".class")) {
+					continue;
+				}
+				String className = je.getName().substring(0, je.getName().length() - CLASS_LENGTH);
+				className = className.replace('/', '.');
+				cl.loadClass(className);
+			}
+
+			// Instantiate the function class
+			fn = (Function) cl.loadClass(entryPoint).newInstance();
+
+		} catch (MalformedURLException e) {
+			e.printStackTrace();
+			return ResponseEntity.badRequest().body("Error loading the Function class file");
+		} catch (ClassNotFoundException e) {
+			e.printStackTrace();
+			return ResponseEntity.badRequest().body("Error loading Function or dependent class");
+		} catch (InstantiationException e) {
+			e.printStackTrace();
+			return ResponseEntity.badRequest().body("Error creating a new instance of function class");
+		} catch (IllegalAccessException e) {
+			e.printStackTrace();
+			return ResponseEntity.badRequest().body("Error creating a new instance of function class");
+		} catch (IOException e) {
+			e.printStackTrace();
+			return ResponseEntity.badRequest().body("Error reading the JAR file");
+		} finally {
+			try {
+				// cl.close();
+				jarFile.close();
+			} catch (IOException e) {
+				e.printStackTrace();
+				return ResponseEntity.badRequest().body("Error closing the file while loading the class");
+			}
+		}
+		long elapsedTime = System.nanoTime() - startTime;
+		logger.log(Level.INFO, "Specialize call done in: " + elapsedTime / 1000000 + " ms");
+		return ResponseEntity.ok("Done");
+	}
+
+	public static void main(String[] args) throws Exception {
+		SpringApplication.run(Server.class, args);
+	}
+
+}