WW-5640 Add WebJars support to Struts core

core/pom.xml

@@ -153,6 +153,17 @@
             <artifactId>caffeine</artifactId>
         </dependency>
 
+        <dependency>
+            <groupId>org.webjars</groupId>
+            <artifactId>webjars-locator-lite</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.webjars</groupId>
+            <artifactId>jquery</artifactId>
+            <scope>test</scope>
+        </dependency>
+
         <dependency>
             <groupId>jakarta.servlet</groupId>
             <artifactId>jakarta.servlet-api</artifactId>

core/src/main/java/org/apache/struts2/StrutsConstants.java

@@ -195,6 +195,16 @@ public final class StrutsConstants {
      */
     public static final String STRUTS_UI_STATIC_CONTENT_PATH = "struts.ui.staticContentPath";
 
+    /**
+     * Whether WebJars support is enabled (serving and URL building)
+     */
+    public static final String STRUTS_WEBJARS_ENABLED = "struts.webjars.enabled";
+
+    /**
+     * Optional comma-separated allowlist of WebJar names permitted to be served (empty = all)
+     */
+    public static final String STRUTS_WEBJARS_ALLOWLIST = "struts.webjars.allowlist";
+
     /**
      * A global flag to enable/disable html body escaping in tags, can be overwritten per tag
      */
@@ -434,6 +444,11 @@ public final class StrutsConstants {
      */
     public static final String STRUTS_STATIC_CONTENT_LOADER = "struts.staticContentLoader";
 
+    /**
+     * The {@link org.apache.struts2.webjars.WebJarUrlProvider} implementation class
+     */
+    public static final String STRUTS_WEBJARS_URL_PROVIDER = "struts.webjars.urlProvider";
+
     /**
      * The {@link org.apache.struts2.UnknownHandlerManager} implementation class
      */

core/src/main/java/org/apache/struts2/components/WebJar.java

@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.struts2.components;
+
+import jakarta.servlet.http.HttpServletRequest;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.struts2.inject.Inject;
+import org.apache.struts2.util.ValueStack;
+import org.apache.struts2.views.annotations.StrutsTag;
+import org.apache.struts2.views.annotations.StrutsTagAttribute;
+import org.apache.struts2.webjars.WebJarUrlProvider;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Optional;
+
+/**
+ * <p>Resolves a version-less WebJar resource path to a servable URL and writes it to the output
+ * (or stores it in a variable when {@code var} is set). Compose it with {@code <s:script>}/{@code <s:link>}
+ * or a raw {@code <link>}/{@code <script>} element.</p>
+ *
+ * <b>Examples</b>
+ * <pre>
+ *   &lt;link rel="stylesheet" href="&lt;s:webjar path="bootstrap/css/bootstrap.min.css" /&gt;" /&gt;
+ *   &lt;@s.webjar path="jquery/jquery.min.js"/&gt;
+ * </pre>
+ */
+@StrutsTag(
+    name = "webjar",
+    tldTagClass = "org.apache.struts2.views.jsp.WebJarTag",
+    description = "Resolve a version-less WebJar resource path to a servable URL")
+public class WebJar extends ContextBean {
+
+    private static final Logger LOG = LogManager.getLogger(WebJar.class);
+
+    protected String path;
+
+    private final HttpServletRequest request;
+    private WebJarUrlProvider webJarUrlProvider;
+
+    public WebJar(ValueStack stack, HttpServletRequest request) {
+        super(stack);
+        this.request = request;
+    }
+
+    @Inject
+    public void setWebJarUrlProvider(WebJarUrlProvider webJarUrlProvider) {
+        this.webJarUrlProvider = webJarUrlProvider;
+    }
+
+    @Override
+    public boolean end(Writer writer, String body) {
+        String logicalPath = findString(path);
+        Optional<String> url = (logicalPath == null)
+            ? Optional.empty()
+            : webJarUrlProvider.resolveUrl(logicalPath, request);
+
+        if (url.isPresent()) {
+            if (StringUtils.isNotBlank(getVar())) {
+                putInContext(url.get());
+            } else {
+                try {
+                    writer.write(url.get());
+                } catch (IOException e) {
+                    LOG.error("Could not write WebJar URL for path '{}'", path, e);
+                }
+            }
+        }
+        return super.end(writer, body);
+    }
+
+    @StrutsTagAttribute(required = true,
+        description = "The version-less WebJar resource path, e.g. bootstrap/css/bootstrap.min.css")
+    public void setPath(String path) {
+        this.path = path;
+    }
+}

core/src/main/java/org/apache/struts2/config/StrutsBeanSelectionProvider.java

@@ -84,6 +84,7 @@
 import org.apache.struts2.validator.ActionValidatorManager;
 import org.apache.struts2.views.freemarker.FreemarkerManager;
 import org.apache.struts2.views.util.UrlHelper;
+import org.apache.struts2.webjars.WebJarUrlProvider;
 
 /**
  * Selects the implementations of key framework extension points, using the loaded
@@ -430,6 +431,7 @@ public void register(ContainerBuilder builder, LocatableProperties props) {
         alias(PatternMatcher.class, StrutsConstants.STRUTS_PATTERNMATCHER, builder, props);
         alias(ContentTypeMatcher.class, StrutsConstants.STRUTS_CONTENT_TYPE_MATCHER, builder, props);
         alias(StaticContentLoader.class, StrutsConstants.STRUTS_STATIC_CONTENT_LOADER, builder, props);
+        alias(WebJarUrlProvider.class, StrutsConstants.STRUTS_WEBJARS_URL_PROVIDER, builder, props);
         alias(UnknownHandlerManager.class, StrutsConstants.STRUTS_UNKNOWN_HANDLER_MANAGER, builder, props);
         alias(UrlHelper.class, StrutsConstants.STRUTS_URL_HELPER, builder, props);
 

core/src/main/java/org/apache/struts2/dispatcher/DefaultStaticContentLoader.java

@@ -27,6 +27,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.struts2.StrutsConstants;
+import org.apache.struts2.webjars.WebJarUrlProvider;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -39,6 +40,8 @@
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
 import java.util.StringTokenizer;
 
 /**
@@ -70,6 +73,8 @@
  */
 public class DefaultStaticContentLoader implements StaticContentLoader {
 
+    protected static final String WEBJARS_REQUEST_PREFIX = "/webjars/";
+
     /**
      * Provide a logging instance.
      */
@@ -107,6 +112,13 @@ public class DefaultStaticContentLoader implements StaticContentLoader {
 
     protected boolean devMode;
 
+    protected WebJarUrlProvider webJarUrlProvider;
+
+    @Inject
+    public void setWebJarUrlProvider(WebJarUrlProvider webJarUrlProvider) {
+        this.webJarUrlProvider = webJarUrlProvider;
+    }
+
     /**
      * Modify state of StrutsConstants.STRUTS_SERVE_STATIC_CONTENT setting.
      *
@@ -209,6 +221,14 @@ protected List<String> parse(String packages) {
     public void findStaticResource(String path, HttpServletRequest request, HttpServletResponse response)
         throws IOException {
         String name = cleanupPath(path);
+
+        if (name.startsWith(WEBJARS_REQUEST_PREFIX)) {
+            if (!findWebJarResource(name, path, request, response)) {
+                sendNotFound(response);
+            }
+            return;
+        }
+
         for (String pathPrefix : pathPrefixes) {
             URL resourceUrl = findResource(buildPath(name, pathPrefix));
             if (resourceUrl != null) {
@@ -231,6 +251,32 @@ public void findStaticResource(String path, HttpServletRequest request, HttpServ
             }
         }
 
+        sendNotFound(response);
+    }
+
+    /**
+     * Resolve and serve a WebJar asset requested under {@code <staticContentPath>/webjars/**}.
+     *
+     * @param name    the request path with the static-content prefix stripped, e.g. {@code /webjars/jquery/jquery.min.js}
+     * @param path    the original request path (used for content-type detection)
+     * @return true if the asset was resolved and streamed; false otherwise (caller sends 404)
+     */
+    protected boolean findWebJarResource(String name, String path, HttpServletRequest request, HttpServletResponse response)
+        throws IOException {
+        String logicalPath = name.substring(WEBJARS_REQUEST_PREFIX.length());
+        Optional<String> resource = webJarUrlProvider.resolveResourcePath(logicalPath);
+        if (resource.isEmpty()) {
+            return false;
+        }
+        URL resourceUrl = findResource(resource.get());
+        if (resourceUrl == null) {
+            return false;
+        }
+        process(resourceUrl.openStream(), path, request, response);
+        return true;
+    }
+
+    protected void sendNotFound(HttpServletResponse response) {
         try {
             response.sendError(HttpServletResponse.SC_NOT_FOUND);
         } catch (IOException e1) {
@@ -321,32 +367,43 @@ protected String buildPath(String name, String packagePrefix) throws Unsupported
     }
 
 
+    /**
+     * Maps a lower-case file extension to its content type. Not using the code provided by
+     * activation.jar to avoid adding yet another dependency; this covers the files we serve up
+     * (Struts' own static assets plus WebJar assets).
+     */
+    private static final Map<String, String> CONTENT_TYPES = Map.ofEntries(
+        Map.entry("js", "text/javascript"),
+        Map.entry("mjs", "text/javascript"),
+        Map.entry("css", "text/css"),
+        Map.entry("html", "text/html"),
+        Map.entry("txt", "text/plain"),
+        Map.entry("gif", "image/gif"),
+        Map.entry("jpg", "image/jpeg"),
+        Map.entry("jpeg", "image/jpeg"),
+        Map.entry("png", "image/png"),
+        Map.entry("svg", "image/svg+xml"),
+        Map.entry("ico", "image/x-icon"),
+        Map.entry("woff2", "font/woff2"),
+        Map.entry("woff", "font/woff"),
+        Map.entry("ttf", "font/ttf"),
+        Map.entry("otf", "font/otf"),
+        Map.entry("eot", "application/vnd.ms-fontobject"),
+        Map.entry("json", "application/json"),
+        Map.entry("map", "application/json"));
+
     /**
      * Determine the content type for the resource name.
      *
      * @param name The resource name
-     * @return The mime type
+     * @return The mime type, or {@code null} if the extension is unknown
      */
     protected String getContentType(String name) {
-        // NOT using the code provided activation.jar to avoid adding yet another dependency
-        // this is generally OK, since these are the main files we server up
-        if (name.endsWith(".js")) {
-            return "text/javascript";
-        } else if (name.endsWith(".css")) {
-            return "text/css";
-        } else if (name.endsWith(".html")) {
-            return "text/html";
-        } else if (name.endsWith(".txt")) {
-            return "text/plain";
-        } else if (name.endsWith(".gif")) {
-            return "image/gif";
-        } else if (name.endsWith(".jpg") || name.endsWith(".jpeg")) {
-            return "image/jpeg";
-        } else if (name.endsWith(".png")) {
-            return "image/png";
-        } else {
+        int dot = name.lastIndexOf('.');
+        if (dot < 0) {
             return null;
         }
+        return CONTENT_TYPES.get(name.substring(dot + 1));
     }
 
     /**

core/src/main/java/org/apache/struts2/views/freemarker/tags/StrutsModels.java

@@ -53,6 +53,7 @@ public class StrutsModels {
     protected RadioModel radio;
     protected SelectModel select;
     protected SetModel set;
+    protected WebJarModel webjar;
     protected SubmitModel submit;
     protected ResetModel reset;
     protected TextAreaModel textarea;
@@ -339,6 +340,13 @@ public SetModel getSet() {
         return set;
     }
 
+    public WebJarModel getWebjar() {
+        if (webjar == null) {
+            webjar = new WebJarModel(stack, req, res);
+        }
+        return webjar;
+    }
+
     public PropertyModel getProperty() {
         if (property == null) {
             property = new PropertyModel(stack, req, res);

core/src/main/java/org/apache/struts2/views/freemarker/tags/WebJarModel.java

@@ -0,0 +1,37 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.struts2.views.freemarker.tags;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.apache.struts2.components.Component;
+import org.apache.struts2.components.WebJar;
+import org.apache.struts2.util.ValueStack;
+
+public class WebJarModel extends TagModel {
+
+    public WebJarModel(ValueStack stack, HttpServletRequest req, HttpServletResponse res) {
+        super(stack, req, res);
+    }
+
+    @Override
+    protected Component getBean() {
+        return new WebJar(stack, req);
+    }
+}