Spring Boot 2.2.2

[Christian Swindler]

Thisguide provides a sampling of how Spring Boot helps you accelerate application development. As you read more Spring Getting Started guides, you will see more use cases for Spring Boot. This guide is meant to give you a quick taste of Spring Boot. If you want to create your own Spring Boot-based project, visit Spring Initializr, fill in your project details, pick your options, and download a bundled up project as a zip file.

Like most Spring Getting Started guides, you can start from scratch and complete each step or you can bypass basic setup steps that are already familiar to you. Either way, you end up with working code.

Spring Boot offers a fast way to build applications. It looks at your classpath and at the beans you have configured, makes reasonable assumptions about what you are missing, and adds those items. With Spring Boot, you can focus more on business features and less on infrastructure.

Is Spring MVC on the classpath? There are several specific beans you almost always need, and Spring Boot adds them automatically. A Spring MVC application also needs a servlet container, so Spring Boot automatically configures embedded Tomcat.

These are just a few examples of the automatic configuration Spring Boot provides. At the same time, Spring Boot does not get in your way. For example, if Thymeleaf is on your path, Spring Boot automatically adds a SpringTemplateEngine to your application context. But if you define your own SpringTemplateEngine with your own settings, Spring Boot does not add one. This leaves you in control with little effort on your part.

The class is flagged as a @RestController, meaning it is ready for use by Spring MVC to handle web requests. @GetMapping maps / to the index() method. When invoked from a browser or by using curl on the command line, the method returns pure text. That is because @RestController combines @Controller and @ResponseBody, two annotations that results in web requests returning data rather than a view.

The Spring Initializr creates a simple application class for you. However, in this case, it is too simple. You need to modify the application class to match the following listing (from src/main/java/com/example/springboot/Application.java):

@EnableAutoConfiguration: Tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings. For example, if spring-webmvc is on the classpath, this annotation flags the application as a web application and activates key behaviors, such as setting up a DispatcherServlet.

There is also a CommandLineRunner method marked as a @Bean, and this runs on start up. It retrieves all the beans that were created by your application or that were automatically added by Spring Boot. It sorts them and prints them out.

MockMvc comes from Spring Test and lets you, through a set of convenient builder classes, send HTTP requests into the DispatcherServlet and make assertions about the result. Note the use of @AutoConfigureMockMvc and @SpringBootTest to inject a MockMvc instance. Having used @SpringBootTest, we are asking for the whole application context to be created. An alternative would be to ask Spring Boot to create only the web layers of the context by using @WebMvcTest. In either case, Spring Boot automatically tries to locate the main application class of your application, but you can override it or narrow it down if you want to build something different.

As well as mocking the HTTP request cycle, you can also use Spring Boot to write a simple full-stack integration test. For example, instead of (or as well as) the mock test shown earlier, we could create the following test (from src/test/java/com/example/springboot/HelloControllerITest.java):

The embedded server starts on a random port because of webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT, and the actual port is configured automatically in the base URL for the TestRestTemplate.

If you are building a web site for your business, you probably need to add some management services. Spring Boot provides several such services (such as health, audits, beans, and more) with its actuator module.

Spring Boot is an open source Java-based framework used to create a micro Service. It is developed by Pivotal Team and is used to build stand-alone and production ready spring applications. This chapter will give you an introduction to Spring Boot and familiarizes you with its basic concepts.

Micro Service is an architecture that allows the developers to develop and deploy services independently. Each service running has its own process and this achieves the lightweight model to support business applications.

Spring Boot provides a good platform for Java developers to develop a stand-alone and production-grade spring application that you can just run. You can get started with minimum configurations without the need for an entire Spring configuration setup.

Spring Boot automatically configures your application based on the dependencies you have added to the project by using @EnableAutoConfiguration annotation. For example, if MySQL database is on your classpath, but you have not configured any database connection, then Spring Boot auto-configures an in-memory database.

Spring Boot Auto Configuration automatically configures your Spring application based on the JAR dependencies you added in the project. For example, if MySQL database is on your class path, but you have not configured any database connection, then Spring Boot auto configures an in-memory database.

The entry point of the Spring Boot Application is the class contains @SpringBootApplication annotation. This class should have the main method to run the Spring Boot application. @SpringBootApplication annotation includes Auto- Configuration, Component Scan, and Spring Boot Configuration.

Spring Boot application scans all the beans and package declarations when the application initializes. You need to add the @ComponentScan annotation for your class file to scan your components added in your project.

I'm having difficulties in debugging a Java spring-boot application on IntelliJ IDEA community Edition. The main problem is, that the IDE won't stop on a breakpoint, even the program surely executes through it. How can I make the the IntelliJ IDEA to stop on the breakpoint?

When running the application in debug mode, the IntelliJ debugger attaches to the Java process that it starts itself (by appending the appropriate parameters, -agentlib:jdwp etc, to the Java command line).

Quite often, these Java processes might then fork a new instance, which is not getting the same parameters, and because it is in a separate process, is not connected to the debugger. This can be confusing.

The spring-boot:run Maven goal, in addition to forking a new JVM, creates even more confusion, because it sometimes does fork and sometimes doesn't, depending on the options it gets, among other things. Some of this can be found in the documentation, but it's not always obvious.

You should first check whether the Java process actually is being debugged at all. When you start the application from IntelliJ, you will see messages scrolling by in the Run / Debug tab. At the top, there's the command line that is being executed. It should contain the debugger parameters (-agentlib:jdwp etc) and it should be followed by a message saying "Connected to the target VM", which is the debugger confirming that it has contact.

Next, if you are unsure if the JVM has been forked, you can check the process list in your OS, for example under MacOS and *nix you can use ps aux grep java. The Java processes typically have a giant parameter list, most of which is the class path. The actual application being run is at the very end of the command line. If the JVM was forked, you have the process running the Maven goal, and another one running the Spring application. Then your debugger will be connected to the process you are not interested in, and your breakpoints won't work.

So go to edit configurations-> Remote -> +. Then start your application normally through intelliJ. Then switch to the newly created remote configuration. Instead of running it, press debug. Now debugger should be ready, and you can set breakpoints and the debugger will stop to them.

You can use this workaround in IntelliJ Community edition to debug java application with standard module (through mvn spring-boot:run) without needing to create a dedicated debug listener in intelliJ configuration (it will be created on the fly) :

NB:the solution provided by @stinger would only work in IntelliJ Idea Ultimate Edition, it will not work in IntelliJ Community Edition, which is the one asked in the question, but I don't have enough reputation yet to add a comment on his answer. @stinger 's solution is yet preferred if you use Ultimate Edition

We assume that the project code is in your local machine (Windows OS) and you have a deployment of your project on an Ubuntu VM in your server (or your VMWare workstation). and these two machines are in the same network (they can ping eachother)

First of all, add the a new Run/Debug configuration using the menu Run>Edit Configuration and then hit the + button at the top left corner and choose the "Remote" option. Keep the configuration parameters as is and just define a name for your new config.

Right click on the top of the putty session window and select "Change Settings.." option. Go to the path Connection>SSH>Tunnels in the left side options tree. Now add two port forwarding records such as the following picture (one Local, which forwards the localhost 5005 port to your remote server IP with the same port number, and one Remote who forwards the remote 5005 port to the 5005 port on localhost machine)

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