Add Java template

template_java/.gitignore

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+# Created by https://www.toptal.com/developers/gitignore/api/java
+# Edit at https://www.toptal.com/developers/gitignore?templates=java
+
+target/
+bin/da_proc.jar
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# End of https://www.toptal.com/developers/gitignore/api/java

template_java/bin/README

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+This is a reserved directory name! Store the binary generated by `build.sh` in this directory

template_java/bin/deploy/README

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+This is a reserved directory name, do not delete or use in your application!

template_java/bin/logs/README

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+This is a reserved directory name, do not delete or use in your application!

template_java/build.sh

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+#!/bin/bash
+
+set -e
+
+# Change the current working directory to the location of the present file
+cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+
+mvn clean compile assembly:single
+mv target/da_project-1.0-SNAPSHOT-jar-with-dependencies.jar bin/da_proc.jar

template_java/cleanup.sh

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+#!/bin/bash
+
+# Change the current working directory to the location of the present file
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )" 
+
+rm -f "$DIR"/bin/da_proc.jar
+rm -rf "$DIR"/target

template_java/pom.xml

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+<?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/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>cs451</groupId>
+  <artifactId>da_project</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>DA_Project</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.11</maven.compiler.source>
+    <maven.compiler.target>1.11</maven.compiler.target>
+  </properties>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+	  <version>3.1.0</version>
+          <configuration>
+            <release>11</release>
+          </configuration>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+	  <version>3.8.1</version>
+          <configuration>
+            <release>11</release>
+          </configuration>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+	  <version>3.2.0</version>
+          <configuration>
+            <release>11</release>
+          </configuration>
+        </plugin>
+        <plugin>
+          <artifactId>maven-assembly-plugin</artifactId>
+          <configuration>
+            <archive>
+              <manifest>
+                <mainClass>cs451.Main</mainClass>
+              </manifest>
+            </archive>
+            <descriptorRefs>
+              <descriptorRef>jar-with-dependencies</descriptorRef>
+            </descriptorRefs>
+          </configuration>
+        </plugin>
+
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

template_java/run.sh

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+#!/bin/bash
+
+# Change the current working directory to the location of the present file
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+
+ret=0
+exec 3>&1; $(java -jar "$DIR"/bin/da_proc.jar "$@" >&3); ret=$?; exec 3>&-
+
+exit $ret

template_java/src/main/java/cs451/BarrierParser.java

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+package cs451;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.InetAddress;
+import java.net.Socket;
+import java.net.UnknownHostException;
+
+public class BarrierParser {
+
+    private static final String BARRIER_KEY = "--barrier";
+
+    private static final int BARRIER_ARGS_NUM = 2;
+    private static final String COLON_REGEX = ":";
+    private static final String IP_START_REGEX = "/";
+
+    private static String ip;
+    private static int port;
+
+    public boolean populate(String key, String value) {
+        if (!key.equals(BARRIER_KEY)) {
+            return false;
+        }
+
+        String[] barrier = value.split(COLON_REGEX);
+        if (barrier.length != BARRIER_ARGS_NUM) {
+            return false;
+        }
+
+        try {
+            String ipTest = InetAddress.getByName(barrier[0]).toString();
+            if (ipTest.startsWith(IP_START_REGEX)) {
+                ip = ipTest.substring(1);
+            } else {
+                ip = InetAddress.getByName(ipTest.split(IP_START_REGEX)[0]).getHostAddress();
+            }
+
+            port = Integer.parseInt(barrier[1]);
+            if (port <= 0) {
+                System.err.println("Barrier port must be a positive number!");
+                return false;
+            }
+        } catch (UnknownHostException e) {
+            e.printStackTrace();
+        }
+
+        return true;
+    }
+
+    public String getIp() {
+        return ip;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+    public static class Barrier {
+
+        public static void waitOnBarrier() {
+            try (Socket socket = new Socket(ip, port)) {
+                InputStream input = socket.getInputStream();
+                InputStreamReader reader = new InputStreamReader(input);
+                System.out.println("Accessing barrier...");
+
+                int character;
+                while ((character = reader.read()) != -1) {}
+            } catch (IOException ex) {
+                System.out.println("I/O error: " + ex.getMessage());
+            }
+        }
+
+    }
+
+}

template_java/src/main/java/cs451/ConfigParser.java

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+package cs451;
+
+import java.io.File;
+
+public class ConfigParser {
+
+    private String path;
+
+    public boolean populate(String value) {
+        File file = new File(value);
+        path = file.getPath();
+        return true;
+    }
+
+    public String getPath() {
+        return path;
+    }
+
+}

template_java/src/main/java/cs451/Constants.java

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+package cs451;
+
+public class Constants {
+
+    public static final int ARG_LIMIT_NO_CONFIG = 8;
+    public static final int ARG_LIMIT_CONFIG = 9;
+
+    // indexes for id
+    public static final int ID_KEY = 0;
+    public static final int ID_VALUE = 1;
+
+    // indexes for hosts
+    public static final int HOSTS_KEY = 2;
+    public static final int HOSTS_VALUE = 3;
+
+    // indexes for barrier
+    public static final int BARRIER_KEY = 4;
+    public static final int BARRIER_VALUE = 5;
+
+    // indexes for output
+    public static final int OUTPUT_KEY = 6;
+    public static final int OUTPUT_VALUE = 7;
+
+    // indexes for config
+    public static final int CONFIG_VALUE = 8;
+}

template_java/src/main/java/cs451/Host.java

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+package cs451;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public class Host {
+
+    private static final String IP_START_REGEX = "/";
+
+    private int id;
+    private String ip;
+    private int port = -1;
+
+    public boolean populate(String idString, String ipString, String portString) {
+        try {
+            id = Integer.parseInt(idString);
+
+            String ipTest = InetAddress.getByName(ipString).toString();
+            if (ipTest.startsWith(IP_START_REGEX)) {
+                ip = ipTest.substring(1);
+            } else {
+                ip = InetAddress.getByName(ipTest.split(IP_START_REGEX)[0]).getHostAddress();
+            }
+
+            port = Integer.parseInt(portString);
+            if (port <= 0) {
+                System.err.println("Port in the hosts file must be a positive number!");
+                return false;
+            }
+        } catch (NumberFormatException e) {
+            if (port == -1) {
+                System.err.println("Id in the hosts file must be a number!");
+            } else {
+                System.err.println("Port in the hosts file must be a number!");
+            }
+            return false;
+        } catch (UnknownHostException e) {
+            e.printStackTrace();
+        }
+
+        return true;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public String getIp() {
+        return ip;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+}

template_java/src/main/java/cs451/HostsParser.java

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+package cs451;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+public class HostsParser {
+
+    private static final String HOSTS_KEY = "--hosts";
+    private static final String SPACES_REGEX = "\\s+";
+
+    private String filename;
+    private List<Host> hosts = new ArrayList<>();
+
+    public boolean populate(String key, String filename) {
+        if (!key.equals(HOSTS_KEY)) {
+            return false;
+        }
+
+        this.filename = filename;
+        try(BufferedReader br = new BufferedReader(new FileReader(filename))) {
+            int lineNum = 1;
+            for(String line; (line = br.readLine()) != null; lineNum++) {
+                if (line.isBlank()) {
+                    continue;
+                }
+
+                String[] splits = line.split(SPACES_REGEX);
+                if (splits.length != 3) {
+                    System.err.println("Problem with the line " + lineNum + " in the hosts file!");
+                    return false;
+                }
+
+                Host newHost = new Host();
+                if (!newHost.populate(splits[0], splits[1], splits[2])) {
+                    return false;
+                }
+
+                hosts.add(newHost);
+            }
+        } catch (IOException e) {
+            System.err.println("Problem with the hosts file!");
+            return false;
+        }
+
+        if (!checkIdRange()) {
+            System.err.println("Hosts ids are not within the range!");
+            return false;
+        }
+
+        // sort by id
+        Collections.sort(hosts, new HostsComparator());
+        return true;
+    }
+
+    private boolean checkIdRange() {
+        int num = hosts.size();
+        for (Host host : hosts) {
+            if (host.getId() < 1 || host.getId() > num) {
+                System.err.println("Id of a host is not in the right range!");
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public boolean inRange(int id) {
+        return id < hosts.size();
+    }
+
+    public List<Host> getHosts() {
+        return hosts;
+    }
+
+    class HostsComparator implements Comparator<Host> {
+
+        public int compare(Host a, Host b) {
+            return a.getId() - b.getId();
+        }
+
+    }
+
+}

template_java/src/main/java/cs451/IdParser.java

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+package cs451;
+
+public class IdParser {
+
+    private static final String ID_KEY = "--id";
+
+    private int id;
+
+    public boolean populate(String key, String value) {
+        if (!key.equals(ID_KEY)) {
+            return false;
+        }
+
+        try {
+            id = Integer.parseInt(value);
+            if (id <= 0) {
+                System.err.println("Id must be a positive number!");
+            }
+        } catch (NumberFormatException e) {
+            System.err.println("Id must be a number!");
+            return false;
+        }
+
+        return true;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+}

template_java/src/main/java/cs451/Main.java

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+package cs451;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.Socket;
+
+public class Main {
+
+    private static void handleSignal() {
+        //immediately stop network packet processing
+        System.out.println("Immediately stopping network packet processing.");
+
+        //write/flush output file if necessary
+        System.out.println("Writing output.");
+    }
+
+    private static void initSignalHandlers() {
+        Runtime.getRuntime().addShutdownHook(new Thread() {
+            @Override
+            public void run() {
+                handleSignal();
+            }
+        });
+    }
+
+    public static void main(String[] args) {
+        Parser parser = new Parser(args);
+        parser.parse();
+
+        initSignalHandlers();
+
+        // example
+        long pid = ProcessHandle.current().pid();
+        System.out.println("My PID is " + pid + ".");
+        System.out.println("Use 'kill -SIGINT " + pid + " ' or 'kill -SIGTERM " + pid + " ' to stop processing packets.");
+
+        System.out.println("My id is " + parser.myId() + ".");
+        System.out.println("List of hosts is:");
+        for (Host host: parser.hosts()) {
+            System.out.println(host.getId() + ", " + host.getIp() + ", " + host.getPort());
+        }
+
+        System.out.println("Barrier: " + parser.barrierIp() + ":" + parser.barrierPort());
+        System.out.println("Output: " + parser.output());
+        // if config is defined; always check before parser.config()
+        if (parser.hasConfig()) {
+            System.out.println("Config: " + parser.config());
+        }
+
+        BarrierParser.Barrier.waitOnBarrier();
+    }
+}

template_java/src/main/java/cs451/OutputParser.java

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+package cs451;
+
+import java.io.File;
+
+public class OutputParser {
+
+    private static final String OUTPUT_KEY = "--output";
+
+    private String path;
+
+    public boolean populate(String key, String value) {
+        if (!key.equals(OUTPUT_KEY)) {
+            return false;
+        }
+
+        File file = new File(value);
+        path = file.getPath();
+        return true;
+    }
+
+    public String getPath() {
+        return path;
+    }
+
+}

template_java/src/main/java/cs451/Parser.java

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+package cs451;
+
+import java.util.List;
+
+public class Parser {
+
+    private String[] args;
+    private long pid;
+    private IdParser idParser;
+    private HostsParser hostsParser;
+    private BarrierParser barrierParser;
+    private OutputParser outputParser;
+    private ConfigParser configParser;
+
+    public Parser(String[] args) {
+        this.args = args;
+    }
+
+    public void parse() {
+        pid = ProcessHandle.current().pid();
+
+        idParser = new IdParser();
+        hostsParser = new HostsParser();
+        barrierParser = new BarrierParser();
+        outputParser = new OutputParser();
+        configParser = null;
+
+        int argsNum = args.length;
+        if (argsNum != Constants.ARG_LIMIT_NO_CONFIG && argsNum != Constants.ARG_LIMIT_CONFIG) {
+            help();
+        }
+
+        if (!idParser.populate(args[Constants.ID_KEY], args[Constants.ID_VALUE])) {
+            help();
+        }
+
+        if (!hostsParser.populate(args[Constants.HOSTS_KEY], args[Constants.HOSTS_VALUE])) {
+            help();
+        }
+
+        if (!hostsParser.inRange(idParser.getId())) {
+            help();
+        }
+
+        if (!barrierParser.populate(args[Constants.BARRIER_KEY], args[Constants.BARRIER_VALUE])) {
+            help();
+        }
+
+        if (!outputParser.populate(args[Constants.OUTPUT_KEY], args[Constants.OUTPUT_VALUE])) {
+            help();
+        }
+
+        if (argsNum == Constants.ARG_LIMIT_CONFIG) {
+            configParser = new ConfigParser();
+            if (!configParser.populate(args[Constants.CONFIG_VALUE])) {
+            }
+        }
+    }
+
+    private void help() {
+        System.err.println("Usage: --id ID --hosts HOSTS --barier NAME:PORT --output OUTPUT [config]");
+        System.exit(1);
+    }
+
+    public int myId() {
+        return idParser.getId();
+    }
+
+    public List<Host> hosts() {
+        return hostsParser.getHosts();
+    }
+
+    public String barrierIp() {
+        return barrierParser.getIp();
+    }
+
+    public int barrierPort() {
+        return barrierParser.getPort();
+    }
+
+    public String output() {
+        return outputParser.getPath();
+    }
+
+    public boolean hasConfig() {
+        return configParser != null;
+    }
+
+    public String config() {
+        return configParser.getPath();
+    }
+
+}