How does Spring Boot load changes in code without restarting the server?

Question

In a Spring Boot application, if you make change in your code, is it possible to see them without restarting the server? If yes, how can that be achieved?

Monetta

Answer 1

Add spring-boot-devtools module to your project, which includes LiveReload server which can be used to trigger a browser refresh whenever a resource has been changed.You can download browser extensions from livereload.com.

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
    </dependency>
</dependencies>

Hierocracy

Answer 2

You only need to add spring-boot-devtools dependency in your pom.xml and yml file property:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <optional>true</optional>
</dependency>

# for not restarting the server every time
spring.devtools.restart.enabled:  false

Gaynor

Answer 3

See the Spring Boot Developer Tools.

Notice:

1. When you change your Java code, the server need to be restarted. The Spring Boot Developer Toolsjust help you to reload it

2. If it is jsp, then you do not have to restart server.

Nehemiah

Answer 4

I'm using intellij, the follow dependency setting works for me.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
    <optional>true</optional>
</dependency> 

Tho

Good answer :) But it's not related to IntelliJ , it's a maven plugin for spring boot development – Quinary

Thank you for the comment, really cool to know that's a solution independent on IDE, I've actually been curious why fg78nc's anwser didn't work for me, any idea what's the effect of tag <scope>runtime</scope> <optional>true</optional> in this context? – Tho

Actually, even with this dependency, hot reloading may not working on IntelliJ out-of-the-box. So, the full solution may also depend on the IDE you're using. – Clarence

Answer 5

Try the following steps and it should work

1. Add the following to pom.xml

   <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>       
            <optional>true</optional>
        </dependency>
   

2. In application.properties

   spring.devtools.restart.enabled=true

Note : Ensure spring boot is restarted once after making changes to the application.properties file.

For additional information please check https://docs.spring.io/spring-boot/docs/1.5.16.RELEASE/reference/html/using-boot-devtools.html

Aforetime

Answer 6

Just enable Build Automatically in the Project tab in STS, if you have the dependency in your pom.xml

Collbaith