SpringApplicationBuilder

last modified August 2, 2023

In this article we show how to use SpringApplicationBuilder to create a simple Spring Boot application.

Spring is a popular Java application framework for creating enterprise applications. Spring Boot is an evolution of Spring framework which helps create stand-alone, production-grade Spring based applications with minimal effort.

SpringApplication

SpringApplication is a class to bootstrap a Spring application from a Java main method. It creates an appropriate ApplicationContext instance (depending on the classpath), registers a CommandLinePropertySource to expose command line arguments as Spring properties, refreshes the application context, loading all singleton beans, and triggers any CommandLineRunner beans.

SpringApplicationBuilder

SpringApplicationBuilder is a builder for SpringApplication and ApplicationContext instances with convenient fluent API and context hierarchy support.

Spring Boot example

The following application is a simple Spring Boot console application which uses SpringApplicationBuilder to set up a Spring Boot application.

The application takes an argument from the user; it expects a full URL of a website and returns its title.

build.gradle … src ├── main │ ├── java │ │ └── com │ │ └── zetcode │ │ ├── Application.java │ │ └── MyRunner.java │ └── resources └── test └── java

This is the project structure.

build.gradle

plugins { id ‘org.springframework.boot’ version ‘3.1.1’ id ‘io.spring.dependency-management’ version ‘1.1.0’ id ‘java’ }

group = ‘com.zetcode’ version = ‘0.0.1-SNAPSHOT’ sourceCompatibility = ‘17’

repositories { mavenCentral() }

dependencies { implementation ‘org.springframework.boot:spring-boot-starter’ implementation ‘org.jsoup:jsoup:1.16.1’ }

Spring Boot starters are a set of convenient dependency descriptors which greatly simplify the configuration. The spring-boot-starter is the core Spring starter. The jsoup dependency is for the JSoup library.

com/zetcode/MyRunner.java

package com.zetcode;

import java.util.List; import org.jsoup.Jsoup; import org.jsoup.nodes.Document; import org.springframework.boot.ApplicationArguments; import org.springframework.boot.ApplicationRunner; import org.springframework.stereotype.Component;

@Component public class MyRunner implements ApplicationRunner {

@Override
public void run(ApplicationArguments args) throws Exception {

    if (!args.containsOption("website")) {

        System.err.println("no website specified");
    } else {

        List<String> vals = args.getOptionValues("website");
        String url = vals.get(0);

        Document doc = Jsoup.connect(url).get();
        String title = doc.title();
        System.out.printf("The title is: %s%n", title);
    }
}

}

After the Spring application is loaded, any bean that implements ApplicationRunner is executed.

if (!args.containsOption(“website”)) {

We check if there is a –website option specified on the command line.

List<String> vals = args.getOptionValues(“website”); String url = vals.get(0);

We get the value of the option.

Document doc = Jsoup.connect(url).get(); String title = doc.title(); System.out.printf(“The title is: %s%n”, title);

With JSoup, we get the title of the specified website.

com/zetcode/Application.java

package com.zetcode;

import org.springframework.boot.Banner; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.builder.SpringApplicationBuilder;

@SpringBootApplication public class Application {

public static void main(String[] args) {

    new SpringApplicationBuilder(Application.class)
            .bannerMode(Banner.Mode.OFF)
            .logStartupInfo(false)
            .build()
            .run(args);
}

}

Application is the entry point which sets up Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.

new SpringApplicationBuilder(Application.class) .bannerMode(Banner.Mode.OFF) .logStartupInfo(false) .build() .run(args);

The SpringApplicationBuilder is used to build the Spring application. We turn off the banner and the startup information.

$ ./gradlew bootRun -q –args=–website=http://webcode.me The title is: My html page

The command line arguments are passed with the –args. The -q (for quiet) is a Gradle option that turns of Gradle messages.

In this article we have covered SpringApplicationBuilder.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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