How to get static resource (js, css) as ClassPathResource in Spring Boot?

Question

I have a requirement to be able to generate PDFs from a Spring Boot Template. For this, I am using a PDF rendering library (FlyingSaucer) which mostly does the job correctly. There is one issue, however: when I have "href" tags on the page, they do not resolve correctly when the PDF renderer tries to render the HTML. For example, if I have the following code:

<link rel="stylesheet" type="text/css" th:href="@{/css/index.css}" />

It resolves correctly in the browser, but when I try to retrieve this as a ClassPath resource using the following code:

new ClassPathResource("/css/index").getInputStream()

Spring Boot says that the file does not exist. This is odd to me, as I thought that Spring Boot adds all static content to the classpath.

Below is the folder structure of my project, which (I think) follows the correct Spring Boot convetion:

Can I get a handle on some Spring resource (through autowiring, the application context, etc) to resolve these URLs just as it does when the browser requests them? I could probably get around this by hardcoding "resources/static/" to the beginning of the url string, but I'd prefer a more dynamic solution.

amant singh · Accepted Answer · 2017-01-12 06:08:29Z

2

Use this:

new ClassPathResource("static/css/index.css").getInputStream();

answered Jan 12, 2017 at 6:08

amant singh

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3 Comments

Pell000 Over a year ago

Is there some way that I dont have to hard code "/static"?

amant singh Over a year ago

In spring, the standard classpath for resources is "src/main/resources". So you will have to append the full path after that. Obviously you can get advantage of pattern matching etc but in the end you will have to provide it anyway.

Pell000 Over a year ago

See my answer. I managed to do this without providing the full path by using some Spring components. I think "src/main/resources/static" is also put on the class path. If my understanding is wrong, however, please let me know.

Pell000 · Accepted Answer · 2017-01-18 05:06:05Z

After trying out various solutions, I managed to come up with one that, despite the answer given by Amant Simgh, doesn't require me to hardcode any paths. I threw a bunch of things at my solution (using images, deploying to a tomcat container, running "bootRun", using webjars), and it seemed to work in every case.

Internally, Spring Boot uses the ResourceHttpRequestHandler class to resolve resources. This allows Spring Boot applications to @Autowire a ResourceHttpRequestHandler bean. So, in order to get a static resource from the backend from java code, you can do the following:

@Autowired
ResourceHttpRequestHandler resourceHandler;

String uri = "/css/mycss.css";
Resource resource;
for (ResourceResolver resourceResolver : resourceHandler.getResourceResolvers())
{
    resource = resourceResolver.resolveResource(null, uri, resourceHandler.getLocations(), null);
    if (resource != null)
        break;
}

This is essentially what SpringBoot is doing when you request a static resource.

IMPORTANT: if your application has a context path (i.e., you deploy a "myapp" application, then the context path will be "/myapp/"), then you must remove the context path from the URI in the example above. Fortunately, this can be easily done through the following:

ServletContext context = // get servlet context somehow
String uriWithoutContext = uri.replace(context.getContextPath(), "");

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