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04a: ⏯ Spring MVC RESTful with JPA, Hibernate & MySQL beginner video tutorial

Related Links 1. Spring MVC RESTful with JPA, Hibernate & MySQL database beginner step by step. … Read more ›...

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04a: ⏯ Spring MVC with Thymeleaf beginner video tutorial

Related Links 1. Spring MVC with Thymeleaf and JavaConfigs. … Read more ›...

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05: Akka tutorial in Java – calculating the factorials concurrently

This tutorial extends the previous tutorial Simple Akka tutorial in Java step by step. This is a non trivial example of calculating the factorial for a range of numbers in parallel. Step 1: The main class “FactorialCalculatorMain.java” takes a range: start and end as input arguments, … Read more ›...

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05: Docker Tutorial – Client & Server on separate containers & networking

In this tutorial, let’s run a Java socket client & a server in two separate Docker containers. Both the client & server are continuously run, and networked by creating a Docker network. MyClient.java

package com.myapp;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class MyClient {
    public static void main(String[] args) throws IOException {
        if (args.length != 1) {
            System.err
                    .println("Pass the server IP as the sole command line argument");
            return;
        }
        try (Socket socket = new Socket(args[0], 8888);
                Scanner sc = new Scanner(System.in);
                Scanner in = new Scanner(socket.getInputStream())) {

            OutputStream os = socket.getOutputStream();
            PrintWriter out = new PrintWriter(os);

            while (true) {
                while(sc.hasNextLine()) {
                    String msg = sc.nextLine();
                    System.out.println("Client sending: " + msg);
                    out.println(msg);
                    out.flush();

                    System.out.println("Server response: " + in.nextLine());
                }
            }
        }
    }
}

package com.myapp;

import java.io.IOException;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.net.Socket;

import java.util.Scanner;

public class MyClient {

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

if (args.length != 1) {

System.err

.println("Pass the server IP as the sole command line argument");

return;

}

try (Socket socket = new Socket(args[0], 8888);

Scanner sc = new Scanner(System.in);

Scanner in = new Scanner(socket.getInputStream())) {

OutputStream os = socket.getOutputStream();

PrintWriter out = new PrintWriter(os);

while (true) {

while(sc.hasNextLine()) {

String msg = sc.nextLine();

System.out.println("Client sending: " + msg);

out.println(msg);

out.flush();

System.out.println("Server response: " + in.nextLine());

}

MyServer.java

package com.myapp;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

public class MyServer {

    public static void main(String[] args) throws IOException {
        try (ServerSocket listener = new ServerSocket(8888)) {
            System.out.println("The server is running...");
            while (true) {
                try (Socket socket = listener.accept();
                        Scanner in = new Scanner(socket.getInputStream())) {
                    PrintWriter out = new PrintWriter(socket.getOutputStream(),
                            true);
                    while (in.hasNextLine()) {
                        String msg = in.nextLine();
                        System.out.println("Server received: " + msg);
                        out.println(msg.toUpperCase());
                    }
                }
            }
        }
    }

}

package com.myapp;

import java.io.IOException;

import java.io.PrintWriter;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.Scanner;

public class MyServer {

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

try (ServerSocket listener = new ServerSocket(8888)) {

System.out.println("The server is running...");

while (true) {

try (Socket socket = listener.accept();

Scanner in = new Scanner(socket.getInputStream())) {

PrintWriter out = new PrintWriter(socket.getOutputStream(),

true);

while (in.hasNextLine()) {

String msg = in.nextLine();

System.out.println("Server received: " + msg);

out.println(msg.toUpperCase());

}

Dockerfile.client

FROM alpine:3.6

MAINTAINER java-success.com
 
WORKDIR /app

USER root

# install required packages
RUN apk add --no-cache openssh openssl openjdk8 rsync bash procps nss maven

# set JAVA_HOME
ENV JAVA_HOME /usr/lib/jvm/java-1.8-openjdk
ENV PATH $PATH:$JAVA_HOME/bin

COPY src/main/java/com/myapp/MyClient.java com/myapp/MyClient.java

RUN javac com/myapp/MyClient.java

EXPOSE 8888
ENTRYPOINT ["java"]
CMD ["com.myapp.MyClient", "myserver"]

FROM alpine:3.6

MAINTAINER java-success.com

WORKDIR /app

USER root

# install required packages

RUN apk add --no-cache openssh openssl openjdk8 rsync bash procps nss maven

# set JAVA_HOME

ENV JAVA_HOME /usr/lib/jvm/java-1.8-openjdk

ENV PATH $PATH:$JAVA_HOME/bin

COPY src/main/java/com/myapp/MyClient.java com/myapp/MyClient.java

RUN javac com/myapp/MyClient.java

EXPOSE 8888

ENTRYPOINT ["java"]

CMD ["com.myapp.MyClient", "myserver"]

Note that “ … Read more ›...

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05: Drools with rules in an excel spreadsheet – Global variables & variable capture

This extends 04: Drools with rules in an excel spreadsheet – Data validation .

Step 1: Enhance the Trade.java POJO with “actualValues” field and “getFieldValue(String fieldNames)” method.


package com.mytutorial.pojo;

import java.lang.reflect.Field;
import org.apache.commons.lang.StringUtils;

public class Trade {
    private String tradeId;
    private String tradeDate;
    private String symbol;
    private String price;
    private String volume;
    private String totalPrice;
    private String buyerId;
    private String sellerId;

    private String actualValues;

    public Trade(String tradeId, String tradeDate, String symbol, String price, String volume, String totalPrice,
            String buyerId, String sellerId) {
        super();
        this.tradeId = tradeId;
        this.tradeDate = tradeDate;
        this.symbol = symbol;
        this.price = price;
        this.volume = volume;
        this.totalPrice = totalPrice;
        this.buyerId = buyerId;
        this.sellerId = sellerId;
    }

    public String getTradeId() {
        return tradeId;
    }

    public void setTradeId(String tradeId) {
        this.tradeId = tradeId;
    }

    public String getTradeDate() {
        return tradeDate;
    }

    public void setTradeDate(String tradeDate) {
        this.tradeDate = tradeDate;
    }

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

    public String getVolume() {
        return volume;
    }

    public void setVolume(String volume) {
        this.volume = volume;
    }

    public String getTotalPrice() {
        return totalPrice;
    }

    public void setTotalPrice(String totalPrice) {
        this.totalPrice = totalPrice;
    }

    public String getBuyerId() {
        return buyerId;
    }

    public void setBuyerId(String buyerId) {
        this.buyerId = buyerId;
    }

    public String getSellerId() {
        return sellerId;
    }

    public void setSellerId(String sellerId) {
        this.sellerId = sellerId;
    }

    public String getActualValues() {
        return actualValues;
    }

    public void setActualValues(String actualValues) {
        this.actualValues = actualValues;
    }

    //reflection to get field values
    public String getFieldValue(String fieldNames) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {

        if (StringUtils.isEmpty(fieldNames)) {
            throw new IllegalArgumentException();
        }

        String[] splits = fieldNames.split("\\,");
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < splits.length; i++) {
            Field field = this.getClass().getDeclaredField(splits[i].trim());
            field.setAccessible(true);
            sb.append((String) field.get(this));

            if (i < splits.length - 1) {
                sb.append("|");
            }
        }

        return sb.toString();
    }

    @Override
    public String toString() {
        return "Trade [tradeId=" + tradeId + ", tradeDate=" + tradeDate + ", symbol=" + symbol + ", price=" + price
                + ", volume=" + volume + ", totalPrice=" + totalPrice + ", buyerId=" + buyerId + ", sellerId="
                + sellerId + ", actualValues=" + actualValues + "]";
    }
}

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package com.mytutorial.pojo;

import java.lang.reflect.Field;

import org.apache.commons.lang.StringUtils;

public class Trade {

private String tradeId;

private String tradeDate;

private String symbol;

private String price;

private String volume;

private String totalPrice;

private String buyerId;

private String sellerId;

private String actualValues;

public Trade(String tradeId, String tradeDate, String symbol, String price, String volume, String totalPrice,

String buyerId, String sellerId) {

super();

this.tradeId = tradeId;

this.tradeDate = tradeDate;

this.symbol = symbol;

this.price = price;

this.volume = volume;

this.totalPrice = totalPrice;

this.buyerId = buyerId;

this.sellerId = sellerId;

}

public String getTradeId() {

return tradeId;

}

public void setTradeId(String tradeId) {

this.tradeId = tradeId;

}

public String getTradeDate() {

return tradeDate;

}

public void setTradeDate(String tradeDate) {

this.tradeDate = tradeDate;

}

public String getSymbol() {

return symbol;

}

public void setSymbol(String symbol) {

this.symbol = symbol;

}

public String getPrice() {

return price;

}

public void setPrice(String price) {

this.price = price;

}

public String getVolume() {

return volume;

}

public void setVolume(String volume) {

this.volume = volume;

}

public String getTotalPrice() {

return totalPrice;

}

public void setTotalPrice(String totalPrice) {

this.totalPrice = totalPrice;

}

public String getBuyerId() {

return buyerId;

}

public void setBuyerId(String buyerId) {

this.buyerId = buyerId;

}

public String getSellerId() {

return sellerId;

}

public void setSellerId(String sellerId) {

this.sellerId = sellerId;

}

public String getActualValues() {

return actualValues;

}

public void setActualValues(String actualValues) {

this.actualValues = actualValues;

}

//reflection to get field values

public String getFieldValue(String fieldNames) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {

if (StringUtils.isEmpty(fieldNames)) {

throw new IllegalArgumentException();

}

String[] splits = fieldNames.split("\\,");

StringBuilder sb = new StringBuilder();

for (int i = 0; i < splits.length; i++) {

Field field = this.getClass().getDeclaredField(splits[i].trim());

field.setAccessible(true);

sb.append((String) field.get(this));

if (i < splits.length - 1) {

sb.append("|");

}

return sb.toString();

}

@Override

public String toString() {

return "Trade [tradeId=" + tradeId + ", tradeDate=" + tradeDate + ", symbol=" + symbol + ", price=" + price

+ ", volume=" + volume + ", totalPrice=" + totalPrice + ", buyerId=" + buyerId + ", sellerId="

+ sellerId + ", actualValues=" + actualValues + "]";

}

Step 2: trades-rules.xls with “

…

05: Kubernetes useful commands with kubectl for development & debugging

This extends Install Kubernetes (i.e. minikube) on Mac.

Step 1: Start the Docker.app on Mac, and then start the minikube cluster from a terminal.


~]$ minikube start

~]$ minikube start

Step 2: Create a pod.yaml manifest file to create a new pod that runs nginx image.

…

05. Spring Cloud routing with Netflix’s Zuul

Q. What is Netflix’s Zuul usecase in Micro Services Architecture? A. In a typical micro service architecture you have many micro services running on different hosts and ports. The challenge with this type of architecture is how different clients like browser based Web Applications, Mobile based apps, … Read more...

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05. ⏯ Getting started with Eclipse & Maven beginner video tutorial

05.Getting started with Eclipse IDE & Maven step by step tutorial

In the tutorial “Setting up Eclipse IDE step by step tutorial” we looked at installing Eclipse IDE, importing an existing Java project folder into eclipse, and creating a Java project within Eclipse. Industrial strength Java applications will be using Eclipse with Maven.

Configure Eclipse to work with Maven

We have already have a modified “settings.xml”

…

05a: ⏯ Spring 4 MVC RESTful Web Service Video Tutorial

05a: ⏯ Spring MVC web app with JPA, Hibernate & MySQL video tutorial

Related Link 1. Spring MVC Web Application with JPA, Hibernate & MySQL step by step. … Read more ›...

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05E. Explain Java and Maven set up via Q&As

This is an extension posts outlining setting up & getting started with Java & Maven.

Q1. What is the difference between JDK & JRE?
A1. JDK: You can download a copy of the Java Development Kit (JDK) for your operating system like Windows 64 bit,

…

06: Capture throughput & latencies with “Metrics Core” tutorial

“Metrics Core” is a very handy framework to gather insights & tune performance of high-throughput and low-latency services. Here is a very simple core Java multi-threaded application that gathers metrics with this library. Step 1: Create a maven project Press enter for all prompts to use the default values. …...

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Blog Archives

04a: ⏯ Spring MVC RESTful with JPA, Hibernate & MySQL beginner video tutorial

04a: ⏯ Spring MVC with Thymeleaf beginner video tutorial

05: Akka tutorial in Java – calculating the factorials concurrently

05: Docker Tutorial – Client & Server on separate containers & networking

05: Drools with rules in an excel spreadsheet – Global variables & variable capture

05: Kubernetes useful commands with kubectl for development & debugging

05. Spring Cloud routing with Netflix’s Zuul

05. ⏯ Getting started with Eclipse & Maven beginner video tutorial

05.Getting started with Eclipse IDE & Maven step by step tutorial

05a: ⏯ Spring 4 MVC RESTful Web Service Video Tutorial

05a: ⏯ Spring MVC web app with JPA, Hibernate & MySQL video tutorial

05E. Explain Java and Maven set up via Q&As

06: Capture throughput & latencies with “Metrics Core” tutorial

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