SpringApplicationBuilder tutorial
last modified July 6, 2020
SpringApplicationBuilder tutorial shows 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.
pom.xml src ├── main │ ├── java │ │ └── com │ │ └── zetcode │ │ ├── Application.java │ │ └── MyRunner.java │ └── resources └── test └── java
This is the project structure.
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>SpringBootApplicationBuilder</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.2.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.jsoup</groupId> <artifactId>jsoup</artifactId> <version>1.12.1</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
Spring Boot starters are a set of convenient dependency descriptors which greatly simplify
Maven configuration. The spring-boot-starter-parent
has some common configurations
for a Spring Boot application. The spring-boot-starter
is the core Spring starter.
The jsoup
dependency is for the JSoup library.
The spring-boot-maven-plugin
provides Spring Boot support in Maven, allowing us
to package executable JAR or WAR archives. Its spring-boot:run
goal runs the
Spring Boot application.
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.
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.
$ mvn -q spring-boot:run -Dspring-boot.run.arguments=--website=http://webcode.me The title is: My html page
This is the output. The command line arguments are passed with
the spring-boot.run.arguments
. The -q
(for quiet)
is a Maven option that turns of Maven messages.
In this tutorial, we have covered SpringApplicationBuilder
.
List Spring Boot tutorials.