Fixes #449.

Author: simonbrowndotje

changelog.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v5.0.1 (unreleased)
+
+-structurizr-core: Fixes https://github.com/structurizr/java/issues/449 (allow text/plain content types when loading themes).
+
 ## v5.0.0 (28th October 2025)
 
 - structurizr-autolayout: Adds support for custom padding view/viewset properties: `structurizr.groupPadding`,`structurizr.boundaryPadding`, and `structurizr.deploymentNodePadding`.

gradle.properties

@@ -5,4 +5,4 @@ signing.secretKeyRingFile=/some/path
 ossrhUsername=username
 ossrhPassword=password
 
-version=5.0.0
+version=5.0.1

structurizr-client/src/main/java/com/structurizr/http/RemoteContent.java

@@ -6,6 +6,7 @@
 public final class RemoteContent {
 
     public static final String CONTENT_TYPE_JSON = "application/json";
+    public static final String CONTENT_TYPE_PLAIN_TEXT = "text/plain";
 
     private final String content;
     private final byte[] bytes;

structurizr-client/src/main/java/com/structurizr/view/ThemeUtils.java

@@ -90,7 +90,7 @@ public static void loadThemes(Workspace workspace, HttpClient httpClient) throws
         for (String themeLocation : workspace.getViews().getConfiguration().getThemes()) {
             if (Url.isUrl(themeLocation)) {
                 RemoteContent remoteContent = httpClient.get(themeLocation);
-                if (remoteContent.getContentType().equals(RemoteContent.CONTENT_TYPE_JSON)) {
+                if (remoteContent.getContentType().startsWith(RemoteContent.CONTENT_TYPE_JSON) || remoteContent.getContentType().startsWith(RemoteContent.CONTENT_TYPE_PLAIN_TEXT)) {
                     Theme theme = fromJson(remoteContent.getContentAsString());
                     String baseUrl = themeLocation.substring(0, themeLocation.lastIndexOf('/') + 1);
 

structurizr-client/src/test/java/com/structurizr/view/ThemeUtilsTests.java

@@ -26,7 +26,7 @@ void loadThemes_DoesNothingWhenNoThemesAreDefined() throws Exception {
 
     @Test
     @Tag("IntegrationTest")
-    void loadThemes_LoadsThemesWhenThemesAreDefined() throws Exception {
+    void loadThemes_LoadsThemesWhenThemesAreDefined_AndContentTypeIsApplicationJson() throws Exception {
         Workspace workspace = new Workspace("Name", "Description");
         SoftwareSystem softwareSystem = workspace.getModel().addSoftwareSystem("Name");
         softwareSystem.addTags("Amazon Web Services - Alexa For Business");
@@ -47,6 +47,29 @@ void loadThemes_LoadsThemesWhenThemesAreDefined() throws Exception {
         assertEquals("https://static.structurizr.com/themes/amazon-web-services-2020.04.30/alexa-for-business.png", style.getIcon());
     }
 
+    @Test
+    @Tag("IntegrationTest")
+    void loadThemes_LoadsThemesWhenThemesAreDefined_AndContentTypeIsPlainText() throws Exception {
+        Workspace workspace = new Workspace("Name", "Description");
+        SoftwareSystem softwareSystem = workspace.getModel().addSoftwareSystem("Name");
+        softwareSystem.addTags("Amazon Web Services - Alexa For Business");
+        workspace.getViews().getConfiguration().setThemes("https://raw.githubusercontent.com/structurizr/themes/refs/heads/master/amazon-web-services-2020.04.30/theme.json");
+
+        HttpClient httpClient = new HttpClient();
+        httpClient.allow(".*");
+        ThemeUtils.loadThemes(workspace, httpClient);
+
+        // there should still be zero styles in the workspace
+        assertEquals(0, workspace.getViews().getConfiguration().getStyles().getElements().size());
+
+        // but we should be able to find a style included in the theme
+        ElementStyle style = workspace.getViews().getConfiguration().getStyles().findElementStyle(softwareSystem);
+        assertNotNull(style);
+        assertEquals("#d6242d", style.getStroke());
+        assertEquals("#d6242d", style.getColor());
+        assertEquals("https://raw.githubusercontent.com/structurizr/themes/refs/heads/master/amazon-web-services-2020.04.30/alexa-for-business.png", style.getIcon());
+    }
+
     @Test
     void toJson() throws Exception {
         Workspace workspace = new Workspace("Name", "Description");