Category: java

how to create spring boot application

Post author By Rajesh Kumar
Post date April 11, 2020
No Comments on how to create spring boot application

database password encryption in spring boot

In this tutorial, we will learn how to create spring boot application

What is Spring boot

Spring Boot makes it easy to create stand-alone, production-grade application. It internally use Spring framework and have embedded tomcat servers, nor need to deploy war in any servers

Also easy to create,configure&run

What You Will learn

End of this tutorial, you will learn to create a spring boot application

Annotation

@SpringBootApplication

Dependency

<parent>                                                              
  <groupId>org.springframework.boot</groupId>                         
  <artifactId>spring-boot-starter-parent</artifactId>                 
  <version>2.2.6.RELEASE</version>                                    
  <relativePath /> <!-- lookup parent from repository -->             
</parent>

Time needed: 30 minutes

Steps

Navigate to Spring initializr website
Click on this url https://start.spring.io/
Choose project as Maven
In this tutorial I am using Maven. You can use gradle or groovy also
Choose language as Java
Here I am using Java. But we have option for Kotlin & Groovy also
Spring Boot Version
Please select the stable version, I am using 2.2.6
Enter Group,artifact,Name & description
Enter the groupid,artifactid&name as you wanted
Packaging as Jar
Choose Jar, But you have option for war also
Java Verison
Here I am using java 8
Add Spring Web as dependency
In case you going you want to expose rest service, Click on the add dependency and select spring web.
Click on the Genreate
Once you filled all these details click on the Generate Button.
It will download .rar format
Extract the downloaded file
Once your download complete, Extract the downloaded .rar file
Import in Eclipse
After Extracting, Import the project in eclipse
Navigate to Main Class
Navigate to Main class which will be under src/main/java
and Make sure the class have @SpringBootApplication annotation
Run
Right click the class and choose the Run As –> Java Application
Verify logs
Once your application starts you can see below logs in console

Tomcat started on port(s): 8080 (http) with context path ''
Updating port to 8080
Started StudentApplication in 22.834 seconds (JVM running for 24.503)

create netflix eureka discovery server using spring boot

register spring boot micro-services to eureka discovery

Tags java, java8, microservices, springboot

microservices spring-boot

register spring boot micro-services to eureka discovery

Post author By Rajesh Kumar
Post date April 10, 2020
No Comments on register spring boot micro-services to eureka discovery

This tutorial is a continuation of our previous tutorial, Here we will learn about register spring boot micro-services to eureka discovery

If you want to learn about eureka please refer my previous post https://beginnersbug.com/create-netflix-eureka-discovery-server-using-spring-boot/

Prerequisite

JDK
Eclipse
Spring boot micro service knowledge
Netflix Eureka knowledge

Annotation used to register

@EnableDiscoveryClient

Dependency

<parent>                                                                
  <groupId>org.springframework.boot</groupId>                           
  <artifactId>spring-boot-starter-parent</artifactId>                   
  <version>2.2.6.RELEASE</version>                                      
  <relativePath /> <!-- lookup parent from repository -->               
</parent> 

<dependency>                                                            
  <groupId>org.springframework.cloud</groupId>                          
  <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>   
</dependency> 

<dependency>                                                            
  <groupId>org.springframework.boot</groupId>                           
  <artifactId>spring-boot-starter-web</artifactId>                      
</dependency>

<dependencyManagement>                                                  
  <dependencies>                                                        
    <dependency>                                                        
      <groupId>org.springframework.cloud</groupId>                      
      <artifactId>spring-cloud-dependencies</artifactId>                
      <version>${spring-cloud.version}</version>                        
      <type>pom</type>                                                  
      <scope>import</scope>                                             
    </dependency>                                                       
  </dependencies>                                                       
</dependencyManagement>

application.properties

server.port=8080
spring.application.name=student
eureka.client.registerWithEureka=true
eureka.client.fetchRegistry=true
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka

Main Class

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class StudentApplication {

	public static void main(String[] args) {
		SpringApplication.run(StudentApplication.class, args);
	}
}

Register spring boot

Time needed: 30 minutes

Steps

Create a spring boot application
Use https://start.spring.io/ to create spring boot application
Add Dependency
Add eureka discovery client and spring web dependency in the text box
Click on the generate
Once you clicked Generate you project will download
Import into your IDE
Import the downloaded project into your IDE. Here I used eclipse IDE for my development
Add @EnableDiscoveryClient annotation
Once you imported you project in IDE, Go to the Main class and add @EnableDiscoveryClient annotation.
This annotation will register spring boot micro-services to eureka discovery
change application.properties
eureka.client.registerWithEureka=true
eureka.client.fetchRegistry=true
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka
Build and Run
Now you can run your application
Testing
Open browser and navigate to http://localhost:8761/
You can see your student micro service under Instances

Exception

In case if you didn’t configure the properties properly, you might get below exception.

TransportException: Cannot execute request on any known server

Solution

Confirm below property in your application.properties

eureka<span class="token punctuation">.</span>client<span class="token punctuation">.</span>serviceUrl<span class="token punctuation">.</span>defaultZone<span class="token operator">=</span>http<span class="token operator">:</span><span class="token operator">/</span><span class="token operator">/</span>localhost<span class="token operator">:</span><span class="token number">8761</span><span class="token operator">/</span>eureka

Make sure your discovery server is running on http://localhost:8761

Github

https://github.com/rkumar9090/student

create netflix eureka discovery server using spring boot

Tags discovery-server, eureka, java, microservices, springboot

microservices spring-boot

create netflix eureka discovery server using spring boot

Post author By Rajesh Kumar
Post date April 8, 2020
No Comments on create netflix eureka discovery server using spring boot

Here we are going to create netflix eureka discovery server using spring boot

What is Discovery Server

Discovery server is an application which hold basic information like host name, port about all the micro-services.

What is Eureka

Eureka is the project name of Discovery server which is created by Netflix.

What is the annotation for discovery server

@EnableEurekaServer

Dependency

<parent>                                                             
  <groupId>org.springframework.boot</groupId>                        
  <artifactId>spring-boot-starter-parent</artifactId>                
  <version>2.2.6.RELEASE</version>                                   
  <relativePath /> <!-- lookup parent from repository -->            
</parent>   

<dependency>                                                         
  <groupId>org.springframework.cloud</groupId>                       
  <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>

<dependencyManagement>                                               
  <dependencies>                                                     
    <dependency>                                                     
      <groupId>org.springframework.cloud</groupId>                   
      <artifactId>spring-cloud-dependencies</artifactId>             
      <version>${spring-cloud.version}</version>                     
      <type>pom</type>                                               
      <scope>import</scope>                                          
    </dependency>                                                    
  </dependencies>                                                    
</dependencyManagement>

pom.xml

https://github.com/rkumar9090/discovery-server/blob/master/pom.xml

application.properties

server.port=8761
eureka.client.registerWithEureka= false
eureka.client.fetchRegistry= false

Main class

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class DiscoveryServerApplication {

	public static void main(String[] args) {
		SpringApplication.run(DiscoveryServerApplication.class, args);
	}
}

How to create Discovery Server

Here we are going to create discovery server with the help of spring boot and with help of some annotation

Time needed: 30 minutes

Steps

Spring Initializer
Navigate to https://start.spring.io/
Add Eureka Server Dependency
In the dependency text box add eureka server as dependency
Click on Generate
Once you entered group id, artifact-id& dependency click on Generate
Import the downloaded project in your favorite IDE
Once you clicked Generate you project will download, after that you can import in your IDE
Add @EnableEurekaServer in the main class
Once you imported you project in IDE, Go to the Main class and add @EnableEurekaServer annotation
Change application.properties
Replace your application.properties with below content
server.port=8761
eureka.client.registerWithEureka= false
eureka.client.fetchRegistry= false
Build and Run
Now you can run your application
Testing
Open browser and navigate to http://localhost:8761/

Register Spring boot with Eureka

Refer below article to register spring boot micro services with eureka discovery server
https://beginnersbug.com/register-spring-boot-micro-services-to-eureka-discovery/

Github

https://github.com/rkumar9090/discovery-server

register spring boot micro-services to eureka discovery

Tags discovery-server, eureka, java, micorservices, netflix, springboot

file java

get the last modified date of a file in Java

Post author By Rajesh Kumar
Post date April 5, 2020
No Comments on get the last modified date of a file in Java

In this post, we will learn about get the last modified date of a file in Java

It returns the value in long format,

we need to use SimpleDateFormat to convert into date format

Syntax

file.lastModified();

Example


import java.io.File;
import java.text.SimpleDateFormat;

public class LastModifedDate {

	public static void main(String[] args) {
		try {
			File file = new File("C:\\Project.log");
		
			if (file.exists()) {
				long lastModified = file.lastModified();

				SimpleDateFormat sdf = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
				System.out.println(sdf.format(lastModified));

			} else {
				System.err.println("File path is not correct ");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/files/LastModifedDate.java

how to read a file from java with example

Tags file, java, lastmodifieddate

Interview java String

count number of words in string using java

Post author By Rajesh Kumar
Post date April 3, 2020
No Comments on count number of words in string using java

In this post, we will learn about count number of words in string using java

In below example we using split method to count number of words in a sentence.

If String have more than one space consecutively, then we need to replace with one string using below code

sentence.replaceAll("\\s+", " ").trim();

Syntax

properString.split(" ");

Example using split

public class CountWords {

	public static void main(String[] args) {

		try {
			String sentence = "    The pen    is mightier than the sword . ";
			String properString = sentence.replaceAll("\\s+", " ").trim();
			String[] split = properString.split(" ");
			System.out.println("The sentence have " + split.length + " words");

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

The sentence have 8 words

Example using StringTokenizer

import java.util.StringTokenizer;

public class CountWords {

	public static void main(String[] args) {
		try {
			String sentence = "    The pen    is mightier than the sword . ";
			StringTokenizer tokens = new StringTokenizer(sentence);
			System.out.println("The sentence have " + tokens.countTokens() + " words");

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

The sentence have 8 words

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/strings/CountWordsUsingSplit.java

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/strings/CountWordsUsingTokenzier.java

find the first occurrence of a character in string using java

Tags count, java, string, words

java String

find the first occurrence of a character in string using java

Post author By Rajesh Kumar
Post date April 1, 2020
No Comments on find the first occurrence of a character in string using java

In this post, we will learn to find the first occurrence of a character in string using java

As like in above image we are going to take String “BeginnersBug” for our example.

This array starts from 0 index to 11.

In this example, we are going to find the first occurrence of character ‘e’. which is 1

Note: that indexOf is case sensitive. It will return -1 if the character is not found

Syntax

	int indexOf = s.indexOf('e');

Example

public class FirstOccurance {

	public static void main(String[] args) {
		try {
			String s = "BeginnersBug";
			int indexOf = s.indexOf('e');
			System.out.println("The first occurance of e is " + indexOf);
		} catch (Exception e) {
			e.printStackTrace();
		}

	}
}

Example

The first occurance of e is 1

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/strings/FirstOccurance.java

find the last index of a character in string using java

Tags firstindex, java, string

java String

find the last index of a character in string using java

Post author By Rajesh Kumar
Post date March 31, 2020
No Comments on find the last index of a character in string using java

In this post, we will learn to find the last index of a character in string using java

As like in above image we are going to take String “BeginnersBug” for our example.

This array starts from 0 index to 11.

In this example, we are going to find the last occurrence of character ‘B’. which is 9

Note: that lastIndexOf is case sensitive. It will return -1 if the character is not found

Syntax

s.lastIndexOf('B');

Example

public class LastIndex {

	public static void main(String[] args) {
		try {
			String s = "BeginnersBug";
			int indexOf = s.lastIndexOf('B');
			System.out.println("The last index of B is " + indexOf);

		} catch (Exception e) {
			e.printStackTrace();
		}

	}
}

Output

The last index of B is 9

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/strings/LastIndex.java

find the first occurrence of a character in string using java

Convert String to lowercase using java

Tags java, lastindex, string

java properties

how to write properties file in java

Post author By Rajesh Kumar
Post date March 29, 2020
No Comments on how to write properties file in java

In this tutorial, we will learn how to write properties file in java

we are going to use FileOutputStream to write in file. It is going to write on classpath

Syntax

properties.store(new FileOutputStream("database.properties"), "Comments: Updated from java");

Example Create new property file

import java.io.FileOutputStream;
import java.util.Properties;

public class WriteProperties {

	public static void main(String[] args) {
		try {

			Properties properties = new Properties();
			properties.setProperty("database.url", "jdbc:mysql://localhost:3306/beginnersbug");
			properties.setProperty("database.username", "root");
			properties.setProperty("database.password", "password");
			properties.store(new FileOutputStream("database.properties"), "Comments: Updated from java");
			System.out.println("File has writen successfully");
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Output

File has writen successfully

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/WriteProperties.java

how to load property file in java

Tags java, properties, write

java

java.sql.SQLTimeoutException Query Timeout

Post author By Rajesh Kumar
Post date March 28, 2020
No Comments on java.sql.SQLTimeoutException Query Timeout

In this tutorial, we will learn about java.sql.SQLTimeoutException Query Timeout

It is always good to do proactive coding. As part of database connection configuration we need to take care of certain parameters

Timeout is one of those properties. If don’t configured well you might get below exception

java.sql.SQLTimeoutException The Query has Timed Out

Root Cause for query timeout

Your application runs a long query with database. you will have this exception.

Solution

setQueryTimeout
- Sets the number of seconds the driver will wait for a Statement object to execute to the given number of seconds.
- default value is 0. which means infinite
setSelectMethod cursor
- By setting the property to “cursor,”. you can create a server-side cursor that can fetch smaller chunks of data at a time
- default value is direct.
setSendStringParametersAsUnicode false
- Set to false string parameters are sent to the server in an ASCII/MBCS format, not in UNICODE
- default value is true

Reference

https://github.com/Microsoft/mssql-jdbc/issues/634

Tags java, sql, timeout

java properties

how to load property file in java

Post author By Rajesh Kumar
Post date March 27, 2020
No Comments on how to load property file in java

In this post, we will learn how to load property file in java. Properties file is used to store and retrieve values from file.

It is stored as key and value pair. Below is an sample property file

database.properties

database.url=jdbc:mysql://localhost:3306/beginnersbug
database.username=root
database.password=password

Read properties from absolute path

import java.io.FileReader;
import java.util.Properties;

public class LoadProperty {

	public static void main(String[] args) {
		try {
			FileReader reader = new FileReader("D:\\BB\\Workspace\\database.properties");

			Properties p = new Properties();
			p.load(reader);

			System.out.println(p.getProperty("database.url"));
			System.out.println(p.getProperty("database.username"));
			System.out.println(p.getProperty("database.password"));

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Output

jdbc:mysql://localhost:3306/beginnersbug
root
password

Read properties from class path

Please make sure you have database.properties in class path. else you will get Please check the file present in classpath

Syntax

LoadPropertyFromClassPath.class.getResourceAsStream("database.properties");


import java.io.InputStream;
import java.util.Properties;

public class LoadPropertyFromClassPath {

	public static void main(String[] args) {
		try {
			Properties prop = new Properties();
			InputStream stream = LoadPropertyFromClassPath.class.getResourceAsStream("database.properties");
			if (stream != null) {
				prop.load(stream);
				System.out.println(prop.getProperty("database.url"));
				System.out.println(prop.getProperty("database.username"));
				System.out.println(prop.getProperty("database.password"));
			} else {
				System.err.println("Please check the file present in classpath");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Output

jdbc:mysql://localhost:3306/beginnersbug
root
password

Print all the values from property file

Syntax

prop.keySet().stream().map(key -> key + ": " + prop.getProperty(key.toString()))
						.forEach(System.out::println);

Example

import java.io.InputStream;
import java.util.Properties;

public class PrintPropertis {

	public static void main(String[] args) {
		try {
			Properties prop = new Properties();
			InputStream stream = LoadPropertyFromClassPath.class.getResourceAsStream("database.properties");
			if (stream != null) {
				prop.load(stream);
				prop.keySet().stream().map(key -> key + ": " + prop.getProperty(key.toString()))
						.forEach(System.out::println);
			} else {
				System.err.println("Please check the file present in classpath");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

Output

database.password: password
database.url: jdbc:mysql://localhost:3306/beginnersbug
database.username: root

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/LoadProperty.java

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/LoadPropertyFromClassPath.java

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/PrintPropertis.java

how to read a file from java with example

delete a file from java code

Tags java, properties

What is Spring boot

What You Will learn

Annotation

Dependency

Related Articles

Prerequisite

Annotation used to register

Dependency

application.properties

Main Class

Register spring boot

Exception

Solution

Github

Related Articles

What is Discovery Server

What is Eureka

What is the annotation for discovery server

Dependency

pom.xml

application.properties

Main class

How to create Discovery Server

Register Spring boot with Eureka

Github

Related Articles

Syntax

Example

Github

Related Articles

Syntax

Example using split

Output

Example using StringTokenizer

Output

Github

Related Articles

Syntax

Example

Example

Github

Related Articles

Syntax

Example

Output

Github

Related Articles

Syntax

Example Create new property file

Output

Github

Related Articles

Root Cause for query timeout

Solution

Reference

database.properties

Read properties from absolute path

Output

Read properties from class path

Syntax

Output

Print all the values from property file

Syntax

Example

Output

Github

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