pref: RSS/Atom (#1342)

* 1.Add the lastBuildDate in RSS.
2.Add the updated in Atom.
3.Change the date format in RSS and Atom
4.Add the lastModified in the response header.

* fix code style

src/main/java/run/halo/app/controller/content/ContentFeedController.java

@@ -5,7 +5,12 @@ import static org.springframework.data.domain.Sort.Direction.DESC;
 import freemarker.template.Template;
 import freemarker.template.TemplateException;
 import java.io.IOException;
+import java.sql.Timestamp;
+import java.text.SimpleDateFormat;
 import java.util.List;
+import java.util.Locale;
+import java.util.OptionalLong;
+import javax.servlet.http.HttpServletResponse;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.RegExUtils;
 import org.springframework.data.domain.Page;
@@ -47,6 +52,8 @@ public class ContentFeedController {
 
     private static final String XML_MEDIA_TYPE = MediaType.APPLICATION_XML_VALUE + UTF_8_SUFFIX;
 
+    private static final String LAST_MODIFIED_HEADER = "Last-Modified";
+
     private final PostService postService;
 
     private final CategoryService categoryService;
@@ -70,7 +77,7 @@ public class ContentFeedController {
     }
 
     /**
-     * Get post rss
+     * Get post rss.
      *
      * @param model model
      * @return rss xml content
@@ -79,8 +86,13 @@ public class ContentFeedController {
      */
     @GetMapping(value = {"feed", "feed.xml", "rss", "rss.xml"}, produces = XML_MEDIA_TYPE)
     @ResponseBody
-    public String feed(Model model) throws IOException, TemplateException {
+    public String feed(Model model, HttpServletResponse response)
-        model.addAttribute("posts", buildPosts(buildPostPageable(optionService.getRssPageSize())));
+        throws IOException, TemplateException {
+        List<PostDetailVO> posts = buildPosts(buildPostPageable(optionService.getRssPageSize()));
+        model.addAttribute("posts", posts);
+        Timestamp lastModified = this.getLastModifiedTime(posts);
+        this.lastModified2ResponseHeader(response, lastModified);
+        model.addAttribute("lastModified", lastModified);
         Template template = freeMarker.getConfiguration().getTemplate("common/web/rss.ftl");
         return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
     }
@@ -97,13 +109,18 @@ public class ContentFeedController {
     @GetMapping(value = {"feed/categories/{slug}",
         "feed/categories/{slug}.xml"}, produces = XML_MEDIA_TYPE)
     @ResponseBody
-    public String feed(Model model, @PathVariable(name = "slug") String slug)
+    public String feed(Model model, @PathVariable(name = "slug") String slug,
+        HttpServletResponse response)
         throws IOException, TemplateException {
         Category category = categoryService.getBySlugOfNonNull(slug);
         CategoryDTO categoryDTO = categoryService.convertTo(category);
+        List<PostDetailVO> posts =
+            buildCategoryPosts(buildPostPageable(optionService.getRssPageSize()), categoryDTO);
         model.addAttribute("category", categoryDTO);
-        model.addAttribute("posts",
+        model.addAttribute("posts", posts);
-            buildCategoryPosts(buildPostPageable(optionService.getRssPageSize()), categoryDTO));
+        Timestamp lastModified = this.getLastModifiedTime(posts);
+        this.lastModified2ResponseHeader(response, lastModified);
+        model.addAttribute("lastModified", lastModified);
         Template template = freeMarker.getConfiguration().getTemplate("common/web/rss.ftl");
         return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
     }
@@ -118,8 +135,13 @@ public class ContentFeedController {
      */
     @GetMapping(value = {"atom", "atom.xml"}, produces = XML_MEDIA_TYPE)
     @ResponseBody
-    public String atom(Model model) throws IOException, TemplateException {
+    public String atom(Model model, HttpServletResponse response)
-        model.addAttribute("posts", buildPosts(buildPostPageable(optionService.getRssPageSize())));
+        throws IOException, TemplateException {
+        List<PostDetailVO> posts = buildPosts(buildPostPageable(optionService.getRssPageSize()));
+        model.addAttribute("posts", posts);
+        Timestamp lastModified = this.getLastModifiedTime(posts);
+        this.lastModified2ResponseHeader(response, lastModified);
+        model.addAttribute("lastModified", lastModified);
         Template template = freeMarker.getConfiguration().getTemplate("common/web/atom.ftl");
         return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
     }
@@ -136,13 +158,18 @@ public class ContentFeedController {
     @GetMapping(value = {"atom/categories/{slug}",
         "atom/categories/{slug}.xml"}, produces = XML_MEDIA_TYPE)
     @ResponseBody
-    public String atom(Model model, @PathVariable(name = "slug") String slug)
+    public String atom(Model model, @PathVariable(name = "slug") String slug,
+        HttpServletResponse response)
         throws IOException, TemplateException {
         Category category = categoryService.getBySlugOfNonNull(slug);
         CategoryDTO categoryDTO = categoryService.convertTo(category);
+        List<PostDetailVO> posts =
+            buildCategoryPosts(buildPostPageable(optionService.getRssPageSize()), categoryDTO);
         model.addAttribute("category", categoryDTO);
-        model.addAttribute("posts",
+        model.addAttribute("posts", posts);
-            buildCategoryPosts(buildPostPageable(optionService.getRssPageSize()), categoryDTO));
+        Timestamp lastModified = this.getLastModifiedTime(posts);
+        this.lastModified2ResponseHeader(response, lastModified);
+        model.addAttribute("lastModified", lastModified);
         Template template = freeMarker.getConfiguration().getTemplate("common/web/atom.ftl");
         return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
     }
@@ -248,4 +275,19 @@ public class ContentFeedController {
         });
         return posts.getContent();
     }
+
+    private Timestamp getLastModifiedTime(List<PostDetailVO> posts) {
+        OptionalLong lastModifiedTimestamp =
+            posts.stream().mapToLong(post -> post.getEditTime().getTime()).max();
+        if (lastModifiedTimestamp.isEmpty()) {
+            return new Timestamp(System.currentTimeMillis());
+        }
+        return new Timestamp(lastModifiedTimestamp.getAsLong());
+    }
+
+    private void lastModified2ResponseHeader(HttpServletResponse response, Timestamp time) {
+        SimpleDateFormat dateFormat =
+            new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.ENGLISH);
+        response.setHeader(LAST_MODIFIED_HEADER, dateFormat.format(time));
+    }
 }

src/main/resources/templates/common/web/atom.ftl

@@ -14,7 +14,7 @@
             <subtitle type="text">${user.description!}</subtitle>
         </#if>
     </#if>
-    <updated>${.now?iso_local}</updated>
+    <updated>${lastModified?iso_local}</updated>
     <#if category??>
         <id>${category.fullPath!}</id>
     <#else>

src/main/resources/templates/common/web/rss.ftl

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
+<#setting locale="en_US">
 <rss version="2.0">
     <channel>
         <#if category??>
@@ -21,6 +22,7 @@
             </#if>
         </#if>
         <generator>Halo ${version!}</generator>
+        <lastBuildDate>${lastModified?string('EEE, dd MMM yyyy HH:mm:ss z')}</lastBuildDate>
         <#if posts?? && posts?size gt 0>
             <#list posts as post>
                 <item>
@@ -35,7 +37,7 @@
                             <![CDATA[${post.summary!}]]>
                         </#if>
                     </description>
-                    <pubDate>${post.createTime?iso_local}</pubDate>
+                    <pubDate>${post.createTime?string('EEE, dd MMM yyyy HH:mm:ss z')}</pubDate>
                 </item>
             </#list>
         </#if>