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
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
Sit On Your Ass Web Development from Jim Nielsen’s Blog

Articles from blogs I follow around the net

Issue 91 – GDP on the blockchain

The regulator set to take on primary crypto oversight is down to a single Commissioner, and new pro-crypto PACs focus on installing more Republicans in the midterms

via Citation Needed August 27, 2025

V&A East Storehouse and Operation Mincemeat in London

We were back in London for a few days and yesterday had a day of culture. First up: the brand new V&A East Storehouse museum in the Queen Elizabeth Olympic Park near Stratford, which opened on May 31st this year. This is a delightful new format for a mu…

via Simon Willison's Weblog: Entries August 27, 2025

St Jude 2025

via Robb Knight • Posts • Atom Feed August 27, 2025

Generated by openring