Use DirectoryBrowserSupport to serve FileParameterValue

This will allow the use of Resource Root URLs for those files.

Additionally, minor UI improvements:
- Explicitly indicate when no file was uploaded
- Do not show original file name on the UI, nobody cares

core/src/main/java/hudson/model/FileParameterValue.java

@@ -226,46 +226,11 @@ public class FileParameterValue extends ParameterValue {
      *
      * @param request
      * @param response
-     * @throws ServletException
-     * @throws IOException
      */
-    public void doDynamic(StaplerRequest request, StaplerResponse response) throws ServletException, IOException {
-        if (("/" + originalFileName).equals(request.getRestOfPath())) {
-            AbstractBuild build = (AbstractBuild)request.findAncestor(AbstractBuild.class).getObject();
-            File fileParameter = getLocationUnderBuild(build);
-
-            if (!ALLOW_FOLDER_TRAVERSAL_OUTSIDE_WORKSPACE) {
-                File fileParameterFolder = getFileParameterFolderUnderBuild(build);
-
-                //TODO can be replaced by Util#isDescendant in 2.80+
-                Path child = fileParameter.getAbsoluteFile().toPath().normalize();
-                Path parent = fileParameterFolder.getAbsoluteFile().toPath().normalize();
-                if (!child.startsWith(parent)) {
-                    throw new IllegalStateException("The fileParameter tried to escape the expected folder: " + location);
-                }
-            }
-
-            if (fileParameter.isFile()) {
-                try (InputStream data = Files.newInputStream(fileParameter.toPath())) {
-                    long lastModified = fileParameter.lastModified();
-                    long contentLength = fileParameter.length();
-                    if (request.hasParameter("view")) {
-                        response.serveFile(request, data, lastModified, contentLength, "plain.txt");
-                    } else {
-                        String csp = SystemProperties.getString(DirectoryBrowserSupport.class.getName() + ".CSP", DirectoryBrowserSupport.DEFAULT_CSP_VALUE);
-                        if (!csp.trim().equals("")) {
-                            // allow users to prevent sending this header by setting empty system property
-                            for (String header : new String[]{"Content-Security-Policy", "X-WebKit-CSP", "X-Content-Security-Policy"}) {
-                                response.setHeader(header, csp);
-                            }
-                        }
-                        response.serveFile(request, data, lastModified, contentLength, originalFileName);
-                    }
-                } catch (InvalidPathException e) {
-                    throw new IOException(e);
-                }
-            }
-        }
+    public DirectoryBrowserSupport doDynamic(StaplerRequest request, StaplerResponse response) {
+        AbstractBuild build = (AbstractBuild)request.findAncestor(AbstractBuild.class).getObject();
+        File fileParameter = getFileParameterFolderUnderBuild(build);
+        return new DirectoryBrowserSupport(build, new FilePath(fileParameter), Messages.FileParameterValue_IndexTitle(), "folder.png", false);
     }
 
     /**

core/src/main/resources/hudson/model/FileParameterValue/value.jelly

@@ -26,16 +26,23 @@ THE SOFTWARE.
 <j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define"
 	xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form"
 	xmlns:i="jelly:fmt" xmlns:p="/lib/hudson/project">
-        <j:set var="escapeEntryTitleAndDescription" value="false"/>
-        <f:entry title="${h.escape(it.name)}" description="${it.formattedDescription}">
-        <j:if test="${it.originalFileName != null}">
-            <j:invokeStatic var="encodedName" className="hudson.Util" method="rawEncode">
-                <j:arg value="${it.name}" />
-            </j:invokeStatic>
-            <j:set var="path" value="parameter/${encodedName}/${it.originalFileName}"/>
-            <a href="${path}">${it.originalFileName}</a>
-            <st:nbsp/>
-            <a href="${path}?view">${%view}</a>
-        </j:if>
+    <j:set var="escapeEntryTitleAndDescription" value="false"/>
+    <f:entry title="${h.escape(it.name)}" description="${it.formattedDescription}">
+        <j:choose>
+            <j:when test="${it.originalFileName != null and it.originalFileName != ''}">
+                <j:invokeStatic var="encodedName" className="hudson.Util" method="rawEncode">
+                    <j:arg value="${it.name}" />
+                </j:invokeStatic>
+                <j:set var="path" value="parameter/${encodedName}/${encodedName}"/>
+                <a href="${path}">${%open}</a>
+                <st:nbsp/>
+                <a href="${path}/*view*">${%view}</a>
+            </j:when>
+            <j:otherwise>
+                <em>
+                    ${%nofile}
+                </em>
+            </j:otherwise>
+        </j:choose>
     </f:entry>
 </j:jelly>

core/src/main/resources/hudson/model/FileParameterValue/value.properties

@@ -0,0 +1 @@
+nofile=(No file was uploaded)

core/src/main/resources/hudson/model/Messages.properties

@@ -412,3 +412,5 @@ ManagementLink.Category.TROUBLESHOOTING=Troubleshooting
 ManagementLink.Category.TOOLS=Tools and Actions
 ManagementLink.Category.MISC=Other
 ManagementLink.Category.UNCATEGORIZED=Uncategorized
+
+FileParameterValue.IndexTitle=File Parameters