[[getting-started]] = Getting started [partintro] -- If you're just getting started with Spring Boot, or 'Spring' in general, this is the section for you! Here we answer the basic "`what?`", "`how?`" and "`why?`" questions. You'll find a gentle introduction to Spring Boot along with installation instructions. We'll then build our first Spring Boot application, discussing some core principles as we go. -- [[getting-started-introducing-spring-boot]] == Introducing Spring Boot Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can "`just run`". We take an opinionated view of the Spring platform and third-party libraries so you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration. You can use Spring Boot to create Java applications that can be started using `java -jar` or more traditional war deployments. We also provide a command line tool that runs "`spring scripts`". Our primary goals are: * Provide a radically faster and widely accessible getting started experience for all Spring development. * Be opinionated out of the box, but get out of the way quickly as requirements start to diverge from the defaults. * Provide a range of non-functional features that are common to large classes of projects (e.g. embedded servers, security, metrics, health checks, externalized configuration). * Absolutely no code generation and no requirement for XML configuration. [[getting-started-system-requirements]] == System Requirements Spring Boot {spring-boot-version} requires http://www.java.com[Java 8] and Spring Framework {spring-version} or above. Explicit build support is provided for Maven (3.2+), and Gradle 4. [[getting-started-system-requirements-servlet-containers]] === Servlet containers The following embedded servlet containers are supported out of the box: |=== |Name |Servlet Version |Tomcat 8.5 |3.1 |Jetty 9.4 |3.1 |Undertow 1.3 |3.1 |=== You can also deploy Spring Boot applications to any Servlet 3.0+ compatible container. [[getting-started-installing-spring-boot]] == Installing Spring Boot Spring Boot can be used with "`classic`" Java development tools or installed as a command line tool. Regardless, you will need http://www.java.com[Java SDK v1.8] or higher. You should check your current Java installation before you begin: [indent=0] ---- $ java -version ---- If you are new to Java development, or if you just want to experiment with Spring Boot you might want to try the <> first, otherwise, read on for "`classic`" installation instructions. [[getting-started-installation-instructions-for-java]] === Installation instructions for the Java developer You can use Spring Boot in the same way as any standard Java library. Simply include the appropriate `+spring-boot-*.jar+` files on your classpath. Spring Boot does not require any special tools integration, so you can use any IDE or text editor; and there is nothing special about a Spring Boot application, so you can run and debug as you would any other Java program. Although you _could_ just copy Spring Boot jars, we generally recommend that you use a build tool that supports dependency management (such as Maven or Gradle). [[getting-started-maven-installation]] ==== Maven installation Spring Boot is compatible with Apache Maven 3.2 or above. If you don't already have Maven installed you can follow the instructions at http://maven.apache.org. TIP: On many operating systems Maven can be installed via a package manager. If you're an OSX Homebrew user try `brew install maven`. Ubuntu users can run `sudo apt-get install maven`. Windows users with Chocolatey can run `choco install maven` from an elevated prompt. Spring Boot dependencies use the `org.springframework.boot` `groupId`. Typically your Maven POM file will inherit from the `spring-boot-starter-parent` project and declare dependencies to one or more <>. Spring Boot also provides an optional <> to create executable jars. Here is a typical `pom.xml` file: [source,xml,indent=0,subs="verbatim,quotes,attributes"] ---- 4.0.0 com.example myproject 0.0.1-SNAPSHOT org.springframework.boot spring-boot-starter-parent {spring-boot-version} org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-maven-plugin ifeval::["{spring-boot-repo}" != "release"] spring-snapshots http://repo.spring.io/snapshot true spring-milestones http://repo.spring.io/milestone spring-snapshots http://repo.spring.io/snapshot spring-milestones http://repo.spring.io/milestone endif::[] ---- TIP: The `spring-boot-starter-parent` is a great way to use Spring Boot, but it might not be suitable all of the time. Sometimes you may need to inherit from a different parent POM, or you might just not like our default settings. See <> for an alternative solution that uses an `import` scope. [[getting-started-gradle-installation]] ==== Gradle installation Spring Boot is compatible with Gradle 4. If you don't already have Gradle installed you can follow the instructions at http://www.gradle.org/. Spring Boot dependencies can be declared using the `org.springframework.boot` `group`. Typically your project will declare dependencies to one or more <>. Spring Boot provides a useful <> that can be used to simplify dependency declarations and to create executable jars. .Gradle Wrapper **** The Gradle Wrapper provides a nice way of "`obtaining`" Gradle when you need to build a project. It's a small script and library that you commit alongside your code to bootstrap the build process. See {gradle-user-guide}/gradle_wrapper.html for details. **** Here is a typical `build.gradle` file: [source,groovy,indent=0,subs="verbatim,attributes"] ---- ifeval::["{spring-boot-repo}" == "release"] plugins { id 'org.springframework.boot' version '{spring-boot-version}' id 'java' } endif::[] ifeval::["{spring-boot-repo}" != "release"] buildscript { repositories { jcenter() maven { url 'http://repo.spring.io/snapshot' } maven { url 'http://repo.spring.io/milestone' } } dependencies { classpath 'org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}' } } apply plugin: 'java' apply plugin: 'org.springframework.boot' apply plugin: 'io.spring.dependency-management' endif::[] jar { baseName = 'myproject' version = '0.0.1-SNAPSHOT' } repositories { jcenter() ifeval::["{spring-boot-repo}" != "release"] maven { url "http://repo.spring.io/snapshot" } maven { url "http://repo.spring.io/milestone" } endif::[] } dependencies { compile("org.springframework.boot:spring-boot-starter-web") testCompile("org.springframework.boot:spring-boot-starter-test") } ---- [[getting-started-installing-the-cli]] === Installing the Spring Boot CLI The Spring Boot CLI is a command line tool that can be used if you want to quickly prototype with Spring. It allows you to run http://groovy.codehaus.org/[Groovy] scripts, which means that you have a familiar Java-like syntax, without so much boilerplate code. You don't need to use the CLI to work with Spring Boot but it's definitely the quickest way to get a Spring application off the ground. [[getting-started-manual-cli-installation]] ==== Manual installation You can download the Spring CLI distribution from the Spring software repository: * http://repo.spring.io/{spring-boot-repo}/org/springframework/boot/spring-boot-cli/{spring-boot-version}/spring-boot-cli-{spring-boot-version}-bin.zip[spring-boot-cli-{spring-boot-version}-bin.zip] * http://repo.spring.io/{spring-boot-repo}/org/springframework/boot/spring-boot-cli/{spring-boot-version}/spring-boot-cli-{spring-boot-version}-bin.tar.gz[spring-boot-cli-{spring-boot-version}-bin.tar.gz] Cutting edge http://repo.spring.io/snapshot/org/springframework/boot/spring-boot-cli/[snapshot distributions] are also available. Once downloaded, follow the {github-raw}/spring-boot-project/spring-boot-cli/src/main/content/INSTALL.txt[INSTALL.txt] instructions from the unpacked archive. In summary: there is a `spring` script (`spring.bat` for Windows) in a `bin/` directory in the `.zip` file, or alternatively you can use `java -jar` with the `.jar` file (the script helps you to be sure that the classpath is set correctly). [[getting-started-sdkman-cli-installation]] ==== Installation with SDKMAN! SDKMAN! (The Software Development Kit Manager) can be used for managing multiple versions of various binary SDKs, including Groovy and the Spring Boot CLI. Get SDKMAN! from http://sdkman.io and install Spring Boot with [indent=0,subs="verbatim,quotes,attributes"] ---- $ sdk install springboot $ spring --version Spring Boot v{spring-boot-version} ---- If you are developing features for the CLI and want easy access to the version you just built, follow these extra instructions. [indent=0,subs="verbatim,quotes,attributes"] ---- $ sdk install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-{spring-boot-version}-bin/spring-{spring-boot-version}/ $ sdk default springboot dev $ spring --version Spring CLI v{spring-boot-version} ---- This will install a local instance of `spring` called the `dev` instance. It points at your target build location, so every time you rebuild Spring Boot, `spring` will be up-to-date. You can see it by doing this: [indent=0,subs="verbatim,quotes,attributes"] ---- $ sdk ls springboot ================================================================================ Available Springboot Versions ================================================================================ > + dev * {spring-boot-version} ================================================================================ + - local version * - installed > - currently in use ================================================================================ ---- [[getting-started-homebrew-cli-installation]] ==== OSX Homebrew installation If you are on a Mac and using http://brew.sh/[Homebrew], all you need to do to install the Spring Boot CLI is: [indent=0] ---- $ brew tap pivotal/tap $ brew install springboot ---- Homebrew will install `spring` to `/usr/local/bin`. NOTE: If you don't see the formula, your installation of brew might be out-of-date. Just execute `brew update` and try again. [[getting-started-macports-cli-installation]] ==== MacPorts installation If you are on a Mac and using http://www.macports.org/[MacPorts], all you need to do to install the Spring Boot CLI is: [indent=0] ---- $ sudo port install spring-boot-cli ---- [[getting-started-cli-command-line-completion]] ==== Command-line completion Spring Boot CLI ships with scripts that provide command completion for http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29[BASH] and http://en.wikipedia.org/wiki/Zsh[zsh] shells. You can `source` the script (also named `spring`) in any shell, or put it in your personal or system-wide bash completion initialization. On a Debian system the system-wide scripts are in `/shell-completion/bash` and all scripts in that directory are executed when a new shell starts. To run the script manually, e.g. if you have installed using SDKMAN! [indent=0] ---- $ . ~/.sdkman/candidates/springboot/current/shell-completion/bash/spring $ spring grab help jar run test version ---- NOTE: If you install Spring Boot CLI using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell. [[getting-started-cli-example]] ==== Quick start Spring CLI example Here's a really simple web application that you can use to test your installation. Create a file called `app.groovy`: [source,groovy,indent=0,subs="verbatim,quotes,attributes"] ---- @RestController class ThisWillActuallyRun { @RequestMapping("/") String home() { "Hello World!" } } ---- Then simply run it from a shell: [indent=0] ---- $ spring run app.groovy ---- NOTE: It will take some time when you first run the application as dependencies are downloaded. Subsequent runs will be much quicker. Open http://localhost:8080 in your favorite web browser and you should see the following output: [indent=0] ---- Hello World! ---- [[getting-started-upgrading-from-an-earlier-version]] === Upgrading from an earlier version of Spring Boot If you are upgrading from an earlier release of Spring Boot check the "`release notes`" hosted on the {github-wiki}[project wiki]. You'll find upgrade instructions along with a list of "`new and noteworthy`" features for each release. To upgrade an existing CLI installation use the appropriate package manager command (for example `brew upgrade`) or, if you manually installed the CLI, follow the <> remembering to update your `PATH` environment variable to remove any older references. [[getting-started-first-application]] == Developing your first Spring Boot application Let's develop a simple "`Hello World!`" web application in Java that highlights some of Spring Boot's key features. We'll use Maven to build this project since most IDEs support it. [TIP] ==== The http://spring.io[spring.io] web site contains many "`Getting Started`" guides that use Spring Boot. If you're looking to solve a specific problem; check there first. You can shortcut the steps below by going to https://start.spring.io and choosing the `web` starter from the dependencies searcher. This will automatically generate a new project structure so that you can <>. Check the https://github.com/spring-io/initializr[documentation for more details]. ==== Before we begin, open a terminal to check that you have valid versions of Java and Maven installed. [indent=0] ---- $ java -version java version "1.8.0_102" Java(TM) SE Runtime Environment (build 1.8.0_102-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode) ---- [indent=0] ---- $ mvn -v Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T16:41:47+00:00) Maven home: /usr/local/Cellar/maven/3.3.9/libexec Java version: 1.8.0_102, vendor: Oracle Corporation ---- NOTE: This sample needs to be created in its own folder. Subsequent instructions assume that you have created a suitable folder and that it is your "`current directory`". [[getting-started-first-application-pom]] === Creating the POM We need to start by creating a Maven `pom.xml` file. The `pom.xml` is the recipe that will be used to build your project. Open your favorite text editor and add the following: [source,xml,indent=0,subs="verbatim,quotes,attributes"] ---- 4.0.0 com.example myproject 0.0.1-SNAPSHOT org.springframework.boot spring-boot-starter-parent {spring-boot-version} ifeval::["{spring-boot-repo}" != "release"] spring-snapshots http://repo.spring.io/snapshot true spring-milestones http://repo.spring.io/milestone spring-snapshots http://repo.spring.io/snapshot spring-milestones http://repo.spring.io/milestone endif::[] ---- This should give you a working build, you can test it out by running `mvn package` (you can ignore the "`jar will be empty - no content was marked for inclusion!`" warning for now). NOTE: At this point you could import the project into an IDE (most modern Java IDE's include built-in support for Maven). For simplicity, we will continue to use a plain text editor for this example. [[getting-started-first-application-dependencies]] === Adding classpath dependencies Spring Boot provides a number of "`Starters`" that make easy to add jars to your classpath. Our sample application has already used `spring-boot-starter-parent` in the `parent` section of the POM. The `spring-boot-starter-parent` is a special starter that provides useful Maven defaults. It also provides a <> section so that you can omit `version` tags for "`blessed`" dependencies. Other "`Starters`" simply provide dependencies that you are likely to need when developing a specific type of application. Since we are developing a web application, we will add a `spring-boot-starter-web` dependency -- but before that, let's look at what we currently have. [indent=0] ---- $ mvn dependency:tree [INFO] com.example:myproject:jar:0.0.1-SNAPSHOT ---- The `mvn dependency:tree` command prints a tree representation of your project dependencies. You can see that `spring-boot-starter-parent` provides no dependencies by itself. Let's edit our `pom.xml` and add the `spring-boot-starter-web` dependency just below the `parent` section: [source,xml,indent=0,subs="verbatim,quotes,attributes"] ---- org.springframework.boot spring-boot-starter-web ---- If you run `mvn dependency:tree` again, you will see that there are now a number of additional dependencies, including the Tomcat web server and Spring Boot itself. [[getting-started-first-application-code]] === Writing the code To finish our application we need to create a single Java file. Maven will compile sources from `src/main/java` by default so you need to create that folder structure, then add a file named `src/main/java/Example.java`: [source,java,indent=0] ---- import org.springframework.boot.*; import org.springframework.boot.autoconfigure.*; import org.springframework.stereotype.*; import org.springframework.web.bind.annotation.*; @RestController @EnableAutoConfiguration public class Example { @RequestMapping("/") String home() { return "Hello World!"; } public static void main(String[] args) throws Exception { SpringApplication.run(Example.class, args); } } ---- Although there isn't much code here, quite a lot is going on. Let's step through the important parts. [[getting-started-first-application-annotations]] ==== The @RestController and @RequestMapping annotations The first annotation on our `Example` class is `@RestController`. This is known as a _stereotype_ annotation. It provides hints for people reading the code, and for Spring, that the class plays a specific role. In this case, our class is a web `@Controller` so Spring will consider it when handling incoming web requests. The `@RequestMapping` annotation provides "`routing`" information. It is telling Spring that any HTTP request with the path "`/`" should be mapped to the `home` method. The `@RestController` annotation tells Spring to render the resulting string directly back to the caller. TIP: The `@RestController` and `@RequestMapping` annotations are Spring MVC annotations (they are not specific to Spring Boot). See the {spring-reference}web.html#mvc[MVC section] in the Spring Reference Documentation for more details. [[getting-started-first-application-auto-configuration]] ==== The @EnableAutoConfiguration annotation The second class-level annotation is `@EnableAutoConfiguration`. This annotation tells Spring Boot to "`guess`" how you will want to configure Spring, based on the jar dependencies that you have added. Since `spring-boot-starter-web` added Tomcat and Spring MVC, the auto-configuration will assume that you are developing a web application and setup Spring accordingly. .Starters and Auto-Configuration **** Auto-configuration is designed to work well with "`Starters`", but the two concepts are not directly tied. You are free to pick-and-choose jar dependencies outside of the starters and Spring Boot will still do its best to auto-configure your application. **** [[getting-started-first-application-main-method]] ==== The "`main`" method The final part of our application is the `main` method. This is just a standard method that follows the Java convention for an application entry point. Our main method delegates to Spring Boot's `SpringApplication` class by calling `run`. `SpringApplication` will bootstrap our application, starting Spring which will in turn start the auto-configured Tomcat web server. We need to pass `Example.class` as an argument to the `run` method to tell `SpringApplication` which is the primary Spring component. The `args` array is also passed through to expose any command-line arguments. [[getting-started-first-application-run]] === Running the example At this point our application should work. Since we have used the `spring-boot-starter-parent` POM we have a useful `run` goal that we can use to start the application. Type `mvn spring-boot:run` from the root project directory to start the application: [indent=0,subs="attributes"] ---- $ mvn spring-boot:run . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v{spring-boot-version}) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.222 seconds (JVM running for 6.514) ---- If you open a web browser to http://localhost:8080 you should see the following output: [indent=0] ---- Hello World! ---- To gracefully exit the application hit `ctrl-c`. [[getting-started-first-application-executable-jar]] === Creating an executable jar Let's finish our example by creating a completely self-contained executable jar file that we could run in production. Executable jars (sometimes called "`fat jars`") are archives containing your compiled classes along with all of the jar dependencies that your code needs to run. .Executable jars and Java **** Java does not provide any standard way to load nested jar files (i.e. jar files that are themselves contained within a jar). This can be problematic if you are looking to distribute a self-contained application. To solve this problem, many developers use "`uber`" jars. An uber jar simply packages all classes, from all jars, into a single archive. The problem with this approach is that it becomes hard to see which libraries you are actually using in your application. It can also be problematic if the same filename is used (but with different content) in multiple jars. Spring Boot takes a <> and allows you to actually nest jars directly. **** To create an executable jar we need to add the `spring-boot-maven-plugin` to our `pom.xml`. Insert the following lines just below the `dependencies` section: [source,xml,indent=0,subs="verbatim,quotes,attributes"] ---- org.springframework.boot spring-boot-maven-plugin ---- NOTE: The `spring-boot-starter-parent` POM includes `` configuration to bind the `repackage` goal. If you are not using the parent POM you will need to declare this configuration yourself. See the {spring-boot-maven-plugin-site}/usage.html[plugin documentation] for details. Save your `pom.xml` and run `mvn package` from the command line: [indent=0,subs="attributes"] ---- $ mvn package [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building myproject 0.0.1-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] .... .. [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ myproject --- [INFO] Building jar: /Users/developer/example/spring-boot-example/target/myproject-0.0.1-SNAPSHOT.jar [INFO] [INFO] --- spring-boot-maven-plugin:{spring-boot-version}:repackage (default) @ myproject --- [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ ---- If you look in the `target` directory you should see `myproject-0.0.1-SNAPSHOT.jar`. The file should be around 10 MB in size. If you want to peek inside, you can use `jar tvf`: [indent=0] ---- $ jar tvf target/myproject-0.0.1-SNAPSHOT.jar ---- You should also see a much smaller file named `myproject-0.0.1-SNAPSHOT.jar.original` in the `target` directory. This is the original jar file that Maven created before it was repackaged by Spring Boot. To run that application, use the `java -jar` command: [indent=0,subs="attributes"] ---- $ java -jar target/myproject-0.0.1-SNAPSHOT.jar . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v{spring-boot-version}) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.536 seconds (JVM running for 2.864) ---- As before, to gracefully exit the application hit `ctrl-c`. [[getting-started-whats-next]] == What to read next Hopefully this section has provided you with some of the Spring Boot basics, and got you on your way to writing your own applications. If you're a task-oriented type of developer you might want to jump over to http://spring.io and check out some of the http://spring.io/guides/[getting started] guides that solve specific "`How do I do that with Spring`" problems; we also have Spring Boot-specific _<>_ reference documentation. The http://github.com/{github-repo}[Spring Boot repository] has also a {github-code}/spring-boot-samples[bunch of samples] you can run. The samples are independent of the rest of the code (that is you don't need to build the rest to run or use the samples). Otherwise, the next logical step is to read _<>_. If you're really impatient, you could also jump ahead and read about _<>_.