Spring Security, Webjars, and MIME type error

May 22, 2017 | java | programming | ci |

I volunteered to be JLO (Java Language Owner) at CircleCI and I am currently working on getting a sample Spring Framework project running on CircleCI 2.0. I made a simple app bootstrapped with the Spring Initializer. I included Spring Security for the first time and I decided to try out WebJars for static Javascript libraries such as bootstrap. I am using Thymeleaf for templating.The app does not actually do anything yet but I ran into a pretty strange issue today that I wanted to write up here. My home page is pretty straightforward.

<!DOCTYPE html>
<html xmlns:th="https://www.thymeleaf.org">
<head>
    <title>CircleCI Spring Demo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<span class="p">&lt;</span><span class="nt">link</span> <span class="na">rel</span><span class="o">=</span><span class="s">"stylesheet"</span> <span class="na">th:href</span><span class="o">=</span><span class="s">"@{/webjars/bootstrap/3.3.7/css/bootstrap.min.css}"</span> <span class="p">/&gt;</span>

<span class="p">&lt;</span><span class="nt">link</span> <span class="na">rel</span><span class="o">=</span><span class="s">"stylesheet"</span> <span class="na">th:href</span><span class="o">=</span><span class="s">"@{/css/style.css}"</span> <span class="na">href</span><span class="o">=</span><span class="s">"../static/css/style.css"</span> <span class="p">/&gt;</span>

</head>
<body>
<span class="p">&lt;</span><span class="nt">nav</span> <span class="na">class</span><span class="o">=</span><span class="s">"navbar"</span><span class="p">&gt;</span>
    <span class="p">&lt;</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"container"</span><span class="p">&gt;</span>
        <span class="p">&lt;</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"navbar-header"</span><span class="p">&gt;</span>
            <span class="p">&lt;</span><span class="nt">a</span> <span class="na">class</span><span class="o">=</span><span class="s">"navbar-brand"</span> <span class="na">href</span><span class="o">=</span><span class="s">"#"</span><span class="p">&gt;</span>CircleCI Demo Spring<span class="p">&lt;/</span><span class="nt">a</span><span class="p">&gt;</span>
        <span class="p">&lt;/</span><span class="nt">div</span><span class="p">&gt;</span>
        <span class="p">&lt;</span><span class="nt">div</span> <span class="na">id</span><span class="o">=</span><span class="s">"navbar"</span> <span class="na">class</span><span class="o">=</span><span class="s">"collapse navbar-collapse"</span><span class="p">&gt;</span>
            <span class="p">&lt;</span><span class="nt">ul</span> <span class="na">class</span><span class="o">=</span><span class="s">"nav navbar-nav"</span><span class="p">&gt;</span>
                <span class="p">&lt;</span><span class="nt">li</span> <span class="na">class</span><span class="o">=</span><span class="s">"active"</span><span class="p">&gt;&lt;</span><span class="nt">a</span> <span class="na">href</span><span class="o">=</span><span class="s">"#"</span><span class="p">&gt;</span>Home<span class="p">&lt;/</span><span class="nt">a</span><span class="p">&gt;&lt;/</span><span class="nt">li</span><span class="p">&gt;</span>
                <span class="p">&lt;</span><span class="nt">li</span><span class="p">&gt;&lt;</span><span class="nt">a</span> <span class="na">href</span><span class="o">=</span><span class="s">"#"</span><span class="p">&gt;</span>About<span class="p">&lt;/</span><span class="nt">a</span><span class="p">&gt;&lt;/</span><span class="nt">li</span><span class="p">&gt;</span>
            <span class="p">&lt;/</span><span class="nt">ul</span><span class="p">&gt;</span>
        <span class="p">&lt;/</span><span class="nt">div</span><span class="p">&gt;</span>
    <span class="p">&lt;/</span><span class="nt">div</span><span class="p">&gt;</span>
<span class="p">&lt;/</span><span class="nt">nav</span><span class="p">&gt;</span>

<span class="p">&lt;</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"container"</span><span class="p">&gt;</span>
    <span class="p">&lt;</span><span class="nt">h1</span><span class="p">&gt;</span> CircleCI Spring Demo <span class="p">&lt;/</span><span class="nt">h1</span><span class="p">&gt;</span>
<span class="p">&lt;/</span><span class="nt">div</span><span class="p">&gt;</span>

<span class="p">&lt;</span><span class="nt">script</span> <span class="na">th:src</span><span class="o">=</span><span class="s">"@{/webjars/bootstrap/3.3.7/js/bootstrap.min.js}"</span><span class="p">&gt;&lt;/</span><span class="nt">script</span><span class="p">&gt;</span>

</body>
</html>

However, when I tried to load up the app with mvn spring-boot:run none of the styles showed up and console showed the following error message:

Resource interpreted as Stylesheet but transferred with MIME type text/html

It turns out, that a default spring-security config will basically block any request unless you whitelist it. The MIME type is a red herring since what is actually happening is that my spring-security config is redirecting all unauthenticated users to my login page (which is login.html) instead of serving up the stylesheet from the/webjars directory. The solution is to update my security configuration to whitelist anything that comes from /webjars

package com.circleci.demojavaspring;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests()
.antMatchers("/", "/home", "/webjars/**").permitAll()
.anyRequest().authenticated()
.and()
.formLogin()
.loginPage("/login")
.permitAll()
.and()
.logout()
.permitAll();
}
}

Now, the styles load as expected.

Thank you for reading! Share your thoughts with me on bluesky, mastodon, or via email.

Check out some more stuff to read down below.

Most popular posts this month

Recent Favorite Blog Posts

This is a collection of the last 8 posts that I bookmarked.

Give Your Spouse the Gift of a Couple's Email Domain from mtlynch.io
Skip the Next iPhone from Articles on Jose M.
Have smart glasses finally hit an inflection point? from The Torment Nexus
The McPhee method from the jsomers.net blog
Pluralistic: LLMs are slot-machines (16 Aug 2025) from Pluralistic: Daily links from Cory Doctorow
Pluralistic: Bluesky creates the world's weirdest, hardest-to-understand binding arbitration clause (15 Aug 2025) from Pluralistic: Daily links from Cory Doctorow
Just a Little More Context Bro, I Promise, and It’ll Fix Everything from Jim Nielsen’s Blog
The Futzing Fraction from Deciphering Glyph

Articles from blogs I follow around the net

Futureverse announces restructuring two years after raising $54 million

In 2023, there was no shortage of buzzy press coverage for Futureverse, which promised to build a metaverse and gaming-focused blockchain. They partnered with Ready Player One author Ernest Cline to build the "Readyverse". Th…

via Web3 is Going Just Great September 30, 2025

New site, kinda

If you’re reading this blog using RSS or via email (when I remember to send the content via email), you likely didn’t notice it. And if you’re reading my blog in the browser but are not a sharp observer, chances are, you also didn’t notice it. A n…

via Manuel Moreale — Everything Feed September 30, 2025

Pluralistic: Announcing the Enshittification tour (30 Sep 2025)

Today's links Announcing the Enshittification tour: Come say hi, why dontcha? Hey look at this: Delights to delectate. Object permanence: HP defeat device; It Gets Better; OPM hack endangers CIA in Beijing; Self-driving cars crash. Upcoming appearance…

via Pluralistic: Daily links from Cory Doctorow September 30, 2025

Generated by openring