Package com.vaadin.flow.internal

Class CssBundler

java.lang.Object
com.vaadin.flow.internal.CssBundler
public class CssBundler extends Object
Utility methods to handle application theme CSS content.

For internal use only. May be renamed or removed in a future release.

Since:
25.1

  • Constructor Details

    • CssBundler

      public CssBundler()

  • Method Details

    • inlineImportsForThemes

      public static String inlineImportsForThemes(File themeFolder, File cssFile, tools.jackson.databind.JsonNode themeJson) throws IOException
      Recurse over CSS import and inlines all ot them into a single CSS block in themes folder under src/main/frontend/themes/<theme-name>.

      Unresolvable imports are put on the top of the resulting code, because @import statements must come before any other CSS instruction, otherwise the import is ignored by the browser.

      Along with import resolution and code inline, URLs (url('image.png') referencing theme resources or assets are rewritten to be correctly served by Vaadin at runtime.

      Parameters:
      themeFolder - location of theme folder on the filesystem.
      cssFile - the CSS file to process.
      themeJson - the theme configuration, usually stored in theme.json file.
      Returns:
      the processed stylesheet content, with inlined imports and rewritten URLs.
      Throws:
      IOException - if filesystem resources can not be read.

    • inlineImports

      public static String inlineImports(File themeFolder, File cssFile, tools.jackson.databind.JsonNode themeJson, File nodeModulesFolder) throws IOException
      Recurse over CSS import and inlines all of them into a single CSS block.

      Unresolvable imports are put on the top of the resulting code, because @import statements must come before any other CSS instruction, otherwise the import is ignored by the browser.

      This overload supports resolving imports from node_modules in addition to relative paths.

      Parameters:
      themeFolder - location of theme folder on the filesystem. May be null if not processing theme files.
      cssFile - the CSS file to process.
      themeJson - the theme configuration, usually stored in theme.json file. May be null.
      nodeModulesFolder - the node_modules folder for resolving npm package imports. May be null if node_modules resolution is not needed.
      Returns:
      the processed stylesheet content, with inlined imports and rewritten URLs.
      Throws:
      IOException - if filesystem resources can not be read.

    • inlineImportsForPublicResources

      public static String inlineImportsForPublicResources(File baseFolder, File cssFile, String contextPath) throws IOException
      Inlines imports for CSS files located under public static resources (e.g. META-INF/resources).
      Parameters:
      baseFolder - base folder the imports and url() references are relative to
      cssFile - the CSS file to process
      contextPath - that url() are rewritten to and rebased onto
      Returns:
      the processed stylesheet content with inlined imports only
      Throws:
      IOException - if filesystem resources cannot be read

    • inlineImportsForStaticResourcesRelative

      public static String inlineImportsForStaticResourcesRelative(File baseFolder, File cssFile, File nodeModulesFolder) throws IOException
      Inlines imports for CSS files located under public static resources (e.g. META-INF/resources) at build time, rewriting relative url(...) references so they are expressed relative to the entry CSS file's folder.

      Unlike inlineImportsForPublicResources(File, File, String), this variant does not prepend a servlet context path. The resulting URLs are purely relative, which is required when the CSS is processed at build time and the deployment context path is not yet known.

      Parameters:
      baseFolder - folder of the entry CSS file; inlined url(...) references are rewritten to paths relative to this folder.
      cssFile - the CSS file to process.
      nodeModulesFolder - the node_modules folder for resolving npm package imports, or null if node_modules resolution is not needed.
      Returns:
      the processed stylesheet content, with inlined imports and rewritten URLs.
      Throws:
      IOException - if filesystem resources cannot be read.
      Since:
      25.1.4

    • minifyCss

      public static String minifyCss(String css)
      Minify CSS content by removing comments and unnecessary whitespace.

      This method performs basic CSS minification:

      • Remove CSS comments
      • Collapse multiple whitespace characters
      • Remove whitespace around special characters like braces and colons
      • Remove trailing semicolons before closing braces
      Parameters:
      css - the CSS content to minify
      Returns:
      the minified CSS content

    • isValidLayerName

      public static boolean isValidLayerName(String layer)
      Returns whether the given value is a valid CSS cascade layer name: one or more CSS identifiers separated by dots, such as theme or theme.base.
      Parameters:
      layer - the layer name to check, not null
      Returns:
      true if the value is a valid layer name

    • validateLayerName

      public static void validateLayerName(String layer)
      Checks that the given value is a valid CSS cascade layer name: one or more CSS identifiers separated by dots, such as theme or theme.base.
      Parameters:
      layer - the layer name to check, not null
      Throws:
      IllegalArgumentException - if the value is not a valid layer name

    • createInvalidLayerNameMessage

      public static String createInvalidLayerNameMessage(String layer)
      Creates the message that explains why the given value is not a valid CSS cascade layer name.
      Parameters:
      layer - the invalid layer name
      Returns:
      the error message

    • createLayerImport

      public static String createLayerImport(String url, String layer)
      Creates a CSS @import rule that loads the style sheet at the given URL into the given cascade layer.

      A <link rel="stylesheet"> cannot put a style sheet into a layer, so a layered style sheet is loaded through this rule in a <style> element instead.

      Parameters:
      url - the URL of the style sheet, not null
      layer - a valid cascade layer name, see validateLayerName(String)
      Returns:
      the @import rule

    • wrapInLayer

      public static String wrapInLayer(String css, String layer)
      Wraps the given style sheet content into a @layer block so that it applies in the given cascade layer.

      The content must not contain @import rules, as those are not allowed inside a block and a browser would silently drop them.

      Parameters:
      css - the style sheet content, not null
      layer - a valid cascade layer name, see validateLayerName(String)
      Returns:
      the content wrapped into a @layer block
      Throws:
      IllegalArgumentException - if the layer name is not valid or the content contains an @import rule