Author: mahmood

Work Queues Sample in RabbitMQ

Server : Consumer

public class Main {

    public static void main(String[] args) throws IOException, TimeoutException {
        String queueName = "queue2";

        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");

        Connection connection = factory.newConnection();

        Channel channel = connection.createChannel();

        channel.queueDeclare(queueName, true, false, false, null);
        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

        channel.basicQos(1);

        Consumer consumer = new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                String message=new String(body,"UTF-8");

                try {
                    doWork(message);
                }
                catch (Exception ex)
                {
                    ex.printStackTrace();
                }
                finally {
                    channel.basicAck(envelope.getDeliveryTag(),false);
                }
            }
        };

        channel.basicConsume(queueName,false,consumer);
    }

    public static void doWork(String message) throws InterruptedException {
        System.out.println(" [x] Received '" + message + "'");

        int sleepTime=new Random().nextInt(2000);

        Thread.sleep(sleepTime);
    }
}

Client : Producer

public class Main {

    public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {

        String queueName = "queue2";

        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");

        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.queueDeclare(queueName, true, false, false, null);

        int count = 0;

        while (count < 100) {

            Date date = new Date();

            String message = String.format("%d : %s", count, date.toString());

            channel.basicPublish("", queueName, MessageProperties.PERSISTENT_TEXT_PLAIN,
                    message.getBytes("UTF-8"));
            System.out.println(String.format(" [x] Sent %s", message));

            Thread.sleep(1000);
            count++;
        }
    }
}

References
https://www.rabbitmq.com/tutorials/tutorial-two-java.html
https://github.com/mhdr/RabbitMQSamples/tree/master/002_WorkQueues

Hello World Sample in RabbitMQ

Server

public class Main {

    public static void main(String[] args) throws IOException, TimeoutException {
        String queueName="Hello";

        ConnectionFactory factory=new ConnectionFactory();
        factory.setHost("localhost");

        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.queueDeclare(queueName,false,false,false,null);

        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");


        Consumer consumer=new DefaultConsumer(channel){
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {

                String message=new String(body,"UTF-8");
                System.out.println(" [x] Received '" + message + "'");
            }
        };

        channel.basicConsume(queueName,true,consumer);
    }
}

Client

public class Main {
    public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {

        String queueName="Hello";

        ConnectionFactory factory=new ConnectionFactory();
        factory.setHost("localhost");

        Connection connection= factory.newConnection();
        Channel channel= connection.createChannel();

        channel.queueDeclare(queueName,false,false,false,null);


        int count=0;

        while (count<100){
            Date date=new Date();
            String message=String.format("Hello World : %s", date.toString());

            channel.basicPublish("",queueName,null,message.getBytes("UTF-8"));

            System.out.println(" [x] Sent '" + message + "'");
            count++;

            Thread.sleep(1000);
        }

        channel.close();
        connection.close();
    }
}

References
https://www.rabbitmq.com/tutorials/tutorial-one-java.html
https://github.com/mhdr/RabbitMQSamples/tree/master/001_HelloWorld

Working with greenDAO on Android

build.gradle

buildscript {
    repositories {
        jcenter()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle

apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"
    defaultConfig {
        applicationId "ir.mhdr.a097"
        minSdkVersion 17
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'org.greenrobot:greendao:3.2.2'

    // This is only needed if you want to use encrypted databases
    compile 'net.zetetic:android-database-sqlcipher:3.5.6'

    testCompile 'junit:junit:4.12'
}

App.java

public class App extends Application {

    public static final boolean ENCRYPTED = false;

    @Override
    public void onCreate() {
        super.onCreate();

        DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(this, ENCRYPTED ? "notes-db-encrypted" : "notes-db");
        Database db = ENCRYPTED ? helper.getEncryptedWritableDb("super-secret") : helper.getWritableDb();
        Statics.daoSession = new DaoMaster(db).newSession();
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="ir.mhdr.a097">

    <application
        android:name=".App"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Statice.java

public class Statics {

    public static DaoSession daoSession;
}

Note.java

@Entity(indexes = {
        @Index(value = "text, date DESC", unique = true)
})
public class Note {

    @Id(autoincrement = true)
    private Long id;

    @Index(unique = true)
    private String uuid;

    @NotNull
    private String text;

    @Property(nameInDb = "date")
    private Date date;

    @Transient
    private int tempUsageCount;

@Generated(hash = 102375063)
public Note(Long id, String uuid, @NotNull String text, Date date) {
    this.id = id;
    this.uuid = uuid;
    this.text = text;
    this.date = date;
}
@Generated(hash = 1272611929)
public Note() {
}
public Long getId() {
    return this.id;
}
public void setId(Long id) {
    this.id = id;
}
public String getText() {
    return this.text;
}
public void setText(String text) {
    this.text = text;
}
public Date getDate() {
    return this.date;
}
public void setDate(Date date) {
    this.date = date;
}
public String getUuid() {
    return this.uuid;
}
public void setUuid(String uuid) {
    this.uuid = uuid;
}
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private DaoSession daoSession;
    private NoteDao noteDao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        daoSession = Statics.daoSession;
        noteDao = daoSession.getNoteDao();

        Note note = new Note();
        note.setUuid(UUID.randomUUID().toString());
        note.setDate(new Date());
        note.setText("Hello World");

        noteDao.save(note);
    }
}

if using Kotlin

android {
    ...
    sourceSets {
        main.java.srcDirs += 'build/generated/source/greendao'
    }
}

References
http://greenrobot.org/greendao/documentation/
https://github.com/mhdr/AndroidSamples/tree/master/097
https://github.com/greenrobot/greenDAO/issues/395

@PathVariable in Spring Boot

    @RequestMapping("/news/{year}/{month}/{day}/{title}")
    public ModelAndView news(HttpServletRequest request, HttpServletResponse response,
                             @PathVariable int year, @PathVariable int month, @PathVariable int day,
                             @PathVariable String title) {

        SessionBL sessionManager = new SessionBL(request, response);

        String postUrl = String.format("/%d/%d/%d/%s", year, month, day, title);

        ModelAndView modelAndView = new ModelAndView("index");
        modelAndView.addObject("version", new Statics().getVersion());
        return modelAndView;
    }

References
http://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html#mvc-ann-requestmapping-uri-templates-regex
https://www.mkyong.com/spring-mvc/spring-rest-requestmapping-extract-incorrectly-if-value-contains/

Install and Manage RabbitMQ on Ubuntu

echo 'deb http://www.rabbitmq.com/debian/ testing main' | sudo tee /etc/apt/sources.list.d/rabbitmq.list
wget -O- https://www.rabbitmq.com/rabbitmq-release-signing-key.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install rabbitmq-server

Enabling the Management Console

sudo rabbitmq-plugins enable rabbitmq_management
http://[your droplet's IP]:15672/

The default username and password are both set “guest” for the log in.

RabbitMQ MQTT Adapter

sudo rabbitmq-plugins enable rabbitmq_mqtt

Managing on Ubuntu

# To start the service:
service rabbitmq-server start

# To stop the service:
service rabbitmq-server stop

# To restart the service:
service rabbitmq-server restart

# To check the status:
service rabbitmq-server status

add new user

rabbitmqctl add_user test test
rabbitmqctl set_user_tags test administrator
rabbitmqctl set_permissions -p / test ".*" ".*" ".*"

delete guest

rabbitmqctl delete_user guest

References
https://www.rabbitmq.com/install-debian.html
https://www.digitalocean.com/community/tutorials/how-to-install-and-manage-rabbitmq
https://www.rabbitmq.com/plugins.html
https://www.rabbitmq.com/man/rabbitmqctl.1.man.html#add_user
https://stackoverflow.com/questions/22850546/cant-access-rabbitmq-web-management-interface-after-fresh-install

Create a Modal Bottom Sheet

build.gradle

compile 'com.android.support:design:<latest-library-version>'

Create a class that extends BottomSheetDialogFragment , inflated with the layout that will be used as the content of the modal dialog.

public class BottomSheetFragment extends BottomSheetDialogFragment {


    public BottomSheetFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_bottom_sheet, container, false);
    }

}

Create an instance of the modal bottom sheet and show it with the show method, passing the FragmentManager and a string tag as parameters.

CustomBottomSheetDialog bottomSheetDialog = CustomBottomSheetDialog.getInstance();
bottomSheetDialog.show(getSupportFragmentManager(), "Custom Bottom Sheet");

References
https://github.com/mhdr/AndroidSamples/tree/master/096
https://mayojava.github.io/android/bottom-sheets-android/