javax.json: Create json and print

Step 1: Define JsonObject instance by setting necessary properties.

JsonObject json = Json.createObjectBuilder()
.add("firstName", "Ram")
.add("lastName", "Gurram")
.add("id", 32)
.add("male", false)
.add("dateOfBirth", new SimpleDateFormat("DD/MM/YYYY").format(date)).build();

 

Step 2: Conver JsonObject to string.

String result = json.toString();

 

Find the below working application.

 

JsonCreateDemo.java

package com.sample.app;

import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Date;

import javax.json.Json;
import javax.json.JsonObject;

public class JsonCreateDemo {

	public static void main(String args[]) {
		LocalDate dateOfBirth = LocalDate.of(1985, 1, 10);
		Date date = Date.from(dateOfBirth.atStartOfDay(ZoneId.systemDefault()).toInstant());

		JsonObject json = Json.createObjectBuilder()
							.add("firstName", "Ram")
							.add("lastName", "Gurram")
							.add("id", 32)
							.add("male", false)
							.add("dateOfBirth", new SimpleDateFormat("DD/MM/YYYY").format(date)).build();
		
		String result = json.toString();

		System.out.println(result);
	}

}

Output

{"firstName":"Ram","lastName":"Gurram","id":32,"male":false,"dateOfBirth":"10/01/1985"}

 

 

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docker: create, start: Create and start the container

'docker create' command is used to create a container, once the container is created, you can start the container using 'docker start' command.

Step 1: Execute the below command to create a container

docker create -p1234:8080 jboss/wildfly

$docker create -p1234:8080 jboss/wildfly
a523924b741accfb04a72d6322c6197c50b4be0b175b8a2d9e087d22d20a1786
$
$docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                           PORTS               NAMES
a523924b741a        jboss/wildfly       "/opt/jboss/wildfly/…"   3 seconds ago       Created                                              silly_cori

From the output, you can observe that container is created with id 'a523924b741a'.

Step 2: Start the container using 'docker start' command.

$docker start a523924b741a
a523924b741a

open the url 'http://localhost:1234/', you can able to see WildFly server home page.

You can even execute the command 'docker ps -a' to check whether container started or not.

$docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS                           PORTS                    NAMES
a523924b741a        jboss/wildfly       "/opt/jboss/wildfly/…"   About a minute ago   Up 50 seconds                    0.0.0.0:1234->8080/tcp   silly_cori

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Javassist: Create new interface at run time

Using ‘makeInterface’ method, you can create new interface.

Step 1: Get an instance of ClassPool.

ClassPool pool = ClassPool.getDefault();

Step 2: Create an interface using makeInterface method.

CtClass ctClass = pool.makeInterface("com.sample.app.interface.Arithmetic");

Step 3: Define methods

CtMethod sum = new CtMethod(CtClass.intType, "sum", new CtClass[] { CtClass.intType, CtClass.intType }, ctClass);

sum.setBody("return $1 + $2;");

CtMethod areaOfCircle = new CtMethod(CtClass.doubleType, "areaOfCircle", new CtClass[] { CtClass.doubleType },ctClass);

Step 4: Add methods to the interface.

ctClass.addMethod(sum);

ctClass.addMethod(areaOfCircle);

Find the below working application.

App.java

package com.sample.app;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;

public class App {

 public static void main(String args[]) throws Exception {
  ClassPool pool = ClassPool.getDefault();

  CtClass ctClass = pool.makeInterface("com.sample.app.interface.Arithmetic");

  CtMethod sum = new CtMethod(CtClass.intType, "sum", new CtClass[] { CtClass.intType, CtClass.intType },
    ctClass);
  sum.setBody("return $1 + $2;");

  CtMethod areaOfCircle = new CtMethod(CtClass.doubleType, "areaOfCircle", new CtClass[] { CtClass.doubleType },
    ctClass);

  ctClass.addMethod(sum);
  ctClass.addMethod(areaOfCircle);

  ctClass.writeFile("/Users/Shared/assistDemos");

 }
}

Run App.java.

You can observe Arithmetic.class file is generated at folder /Users/Shared/assistDemos.

$tree /Users/Shared/assistDemos
/Users/Shared/assistDemos
└── com
    └── sample
        └── app
            └── interface
                └── Arithmetic.class

4 directories, 1 file

Open Arithmetic.class file in decompiler to see the source code.

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Create file parent directories if they are not exist

Below snippet is used to create parent directories of the file, if those are not exist.

String directoryPath = "Enter file absolute path here";

File file = new File(directoryPath);

file.getParentFile().mkdirs();

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Get File size in java

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