Updating spring boot static resources after deploying JAR file

Question

I have developed a REST API with Spring Boot. I've used Angular for front-end and added its files to resources/static. Everything is working fine.

I currently deploy my application in fat JAR format. The spring boot application does not change very often but I have to change the front-end day by day. Is there any way to somehow inject the updated angular files to currently deployed JAR file? Or I should change the packaging to WAR and use external tomcat server?

Answer 1

Literally, yes, you can update an existing jar file by using the jar command :

jar uf jar-file input-file(s)

However, you still need to restart the process.

I assume, your question is more about hot deployment or hot swapping - how to add new files without stopping a running process.

In the case of a spring-boot application with an embedded Tomcat in a production environment , you still need to restart it.

So, the easiest way to achieve a hot deploy of an angular front-end is to split your jar, extract an angular app, and deploy it separately.

As you mentioned, you can deploy a war with an angular app to a Tomcat instance. If you use a Linux based machine, I would recommend packing the angular app to a tar/zip and extracting it to an Apache httpd or nginx web server.

Also, you can use, for example, docker-compose for live reloading .

In the case of a development environment , it's much easier, because you can make use of an IDE support combined with spring-boot-devtools to achieve hot swapping, more explained at spring-boot docs .

Answer 2

In theory you can define any directory as source of your static files:

@Configuration
public class ResourceConfig implements WebMvcConfigurer{

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry
      .addResourceHandler("/resources/**")
      .addResourceLocations("file:///e:/app/resources/public/")
     //other options
}}

No idea if it works in production, I've done some prototyping only. There is a bit more on Baeldung page (old article, but updated to Spring 5), and official spring docs