[JavaWorker] Enable java worker support (#2094)

* Enable java worker support
--------------------------
This commit includes a tailored version of the Java worker implementation from Ant Financial.
The changes for build system, python module, src module and arrow are in other commits, this commit consists of the following modules:
 - java/api: Ray API definition
 - java/common: utilities
 - java/hook: binary rewrite of the Java byte-code for remote execution
 - java/runtime-common: common implementation of the runtime in worker
 - java/runtime-dev: a pure-java mock implementation of the runtime for fast development
 - java/runtime-native: a native implementation of the runtime
 - java/test: various tests

Contributors for this work:
 Guyang Song, Peng Cao, Senlin Zhu,Xiaoying Chu, Yiming Yu, Yujie Liu, Zhenyu Guo

* change the format of java help document from markdown to RST

* update the vesion of Arrow for java worker

* adapt the new version of plasma java client from arrow which use byte[] instead of custom type

* add java worker test to ci

* add the example module for better usage guide

java/example/pom.xml

@@ -0,0 +1,102 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<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/maven-v4_0_0.xsd">
+  <parent>
+    <groupId>org.ray.parent</groupId>
+    <artifactId>ray-superpom</artifactId>
+    <version>1.0</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.ray</groupId>
+  <artifactId>ray-example</artifactId>
+
+  <name>java example for ray</name>
+  <description>java example for ray</description>
+  <url></url>
+
+  <packaging>jar</packaging>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-api</artifactId>
+      <version>1.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-runtime-common</artifactId>
+      <version>1.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-runtime-native</artifactId>
+      <version>1.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-runtime-dev</artifactId>
+      <version>1.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-common</artifactId>
+      <version>1.0</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.ray</groupId>
+      <artifactId>ray-hook</artifactId>
+      <version>1.0</version>
+    </dependency>
+  </dependencies>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>2.20.1</version>
+        <configuration>
+          <environmentVariables>
+            <RAY_CONFIG>${basedir}/../ray.config.ini</RAY_CONFIG>
+          </environmentVariables>
+          <argLine>-ea
+            -Djava.library.path=${basedir}/../../build/src/plasma:${basedir}/../../build/src/local_scheduler
+            -noverify
+            -DlogOutput=console
+          </argLine>
+          <testSourceDirectory>${basedir}/src/main/java/</testSourceDirectory>
+          <testClassesDirectory>${project.build.directory}/classes/</testClassesDirectory>
+        </configuration>
+      </plugin>
+
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-dependency-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>copy-dependencies</id>
+            <phase>package</phase>
+            <goals>
+              <goal>copy-dependencies</goal>
+            </goals>
+            <configuration>
+              <outputDirectory>${basedir}/lib</outputDirectory>
+              <overWriteReleases>false</overWriteReleases>
+              <overWriteSnapshots>false</overWriteSnapshots>
+              <overWriteIfNewer>true</overWriteIfNewer>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+
+    </plugins>
+  </build>
+
+</project>

java/example/run.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+#first you should run the ../test.sh to build
+ROOT_DIR=$(cd "$(dirname "${BASH_SOURCE:-$0}")"; pwd)
+export RAY_CONFIG=$ROOT_DIR/../ray.config.ini
+java -Djava.library.path=../../build/src/plasma:../../build/src/local_scheduler -cp .:target/ray-example-1.0.jar:lib/* org.ray.example.HelloWorld

java/example/src/main/java/org/ray/example/HelloWorld.java

@@ -0,0 +1,56 @@
+package org.ray.example;
+
+import org.ray.api.Ray;
+import org.ray.api.RayObject;
+import org.ray.api.RayRemote;
+import org.ray.core.RayRuntime;
+import org.ray.util.logger.RayLog;
+
+import java.io.Serializable;
+
+public class HelloWorld implements Serializable{
+
+
+  public static String sayHelloWorld() {
+    RayObject<String> hello = Ray.call(HelloWorld::sayHello);
+    RayObject<String> world = Ray.call(HelloWorld::sayWorld);
+    return Ray.call(HelloWorld::merge, hello, world).get();
+  }
+
+  @RayRemote
+  public static String sayHello() {
+    String ret = "he";
+    ret += "llo";
+    RayLog.rapp.info("real say hello");
+    return ret;
+  }
+
+  @RayRemote
+  public static String sayWorld() {
+    String ret = "world";
+    ret += "!";
+    return ret;
+  }
+
+  @RayRemote
+  public static String merge(String hello, String world) {
+    return hello + "," + world;
+  }
+
+  public static void main(String[] args) throws Exception {
+    try {
+        Ray.init();
+        String helloWorld = HelloWorld.sayHelloWorld();
+        RayLog.rapp.info(helloWorld);
+        assert helloWorld.equals("hello,world!");
+    }
+    catch (Throwable t) {
+      t.printStackTrace();
+    }
+    finally {
+      RayRuntime.getInstance().cleanUp();
+    }
+
+
+  }
+}