From f4a4051dca40f99db1d84e6967dafbb6b1af647d Mon Sep 17 00:00:00 2001
From: Jean-Philippe Orsini <orsinije@fr.ibm.com>
Date: Tue, 17 Oct 2017 00:46:24 +0200
Subject: [PATCH] avoid duplicate article instances

---
 war/pom.xml                                        |  4 +--
 .../main/java/pnews/servlet/ArticleFactory.java    |  8 +++++
 .../main/java/pnews/servlet/ArticleProvider.java   | 15 +++++----
 war/src/main/java/pnews/servlet/ArticleStore.java  | 36 ++++++++++++++++++++++
 4 files changed, 53 insertions(+), 10 deletions(-)
 create mode 100644 war/src/main/java/pnews/servlet/ArticleFactory.java
 create mode 100644 war/src/main/java/pnews/servlet/ArticleStore.java

diff --git a/war/pom.xml b/war/pom.xml
index 3b1f825..e68b9c6 100644
--- a/war/pom.xml
+++ b/war/pom.xml
@@ -8,8 +8,8 @@
 
         <properties>
                 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-                <maven.compiler.source>1.7</maven.compiler.source>
-                <maven.compiler.target>1.7</maven.compiler.target>
+                <maven.compiler.source>1.8</maven.compiler.source>
+                <maven.compiler.target>1.8</maven.compiler.target>
         </properties>
 
         <dependencies>
diff --git a/war/src/main/java/pnews/servlet/ArticleFactory.java b/war/src/main/java/pnews/servlet/ArticleFactory.java
new file mode 100644
index 0000000..b89bebb
--- /dev/null
+++ b/war/src/main/java/pnews/servlet/ArticleFactory.java
@@ -0,0 +1,8 @@
+package pnews.servlet;
+
+import pnews.Article;
+
+@FunctionalInterface
+public interface ArticleFactory {
+        Article create();
+}
diff --git a/war/src/main/java/pnews/servlet/ArticleProvider.java b/war/src/main/java/pnews/servlet/ArticleProvider.java
index c6cad50..d3e4f3d 100644
--- a/war/src/main/java/pnews/servlet/ArticleProvider.java
+++ b/war/src/main/java/pnews/servlet/ArticleProvider.java
@@ -120,10 +120,10 @@ public class ArticleProvider {
                 return false;
         }
         
-        private Article toArticle(String link, Category cat, SyndEntry entry, SyndFeed feed) {
+        private static Article toArticle(String link, SyndEntry entry, SyndFeed feed) {
                 String desc, title, thumbnail;
                 Date date;
-
+                
                 thumbnail = null;
                 for (SyndEnclosure e: entry.getEnclosures()) {
                         if (e.getType().startsWith("image/"))
@@ -151,9 +151,9 @@ public class ArticleProvider {
                                      
                 return new Article(link, title, desc, thumbnail, date, title);
         }
-                            
+        
         private void addArticles(Category cat, SyndFeed feed) {
-                String link, feedTitle;
+                String feedTitle;
                 List<Article> articles;
                 Article a;
                 
@@ -162,14 +162,14 @@ public class ArticleProvider {
                 LOG.info("addArticles " + cat.getId() + " " + feedTitle + " number of articles: " + feed.getEntries().size());
                 
                 for (SyndEntry entry: feed.getEntries()) {
-                        link = entry.getLink().trim();
+                        String link = entry.getLink().trim();
                         articles = getArticlesForUpdate(cat);
                         if (exists(link, articles)) {
                                 LOG.fine("addArticles " + link + " is already present");
                                 continue ;
                         }
                         
-                        a = toArticle(link, cat, entry, feed);                        
+                        a = ArticleStore.singleton.getArticle(link, ()->toArticle(link, entry, feed));
                         
                         synchronized (articles) {
                                 articles.add(a);
@@ -185,14 +185,13 @@ public class ArticleProvider {
                                                         return -1;
                                                 return o2.publicationDate.compareTo(o1.publicationDate);
                                         }
-
                                 });
                         }
                 }          
                 
                 LOG.info("addArticles done " + cat.getId());
         }
-        
+             
         private void retrieveArticles(Category cat) throws IllegalArgumentException, MalformedURLException, FeedException, IOException {
                 String[] feeds;
                 
diff --git a/war/src/main/java/pnews/servlet/ArticleStore.java b/war/src/main/java/pnews/servlet/ArticleStore.java
new file mode 100644
index 0000000..0b40cc3
--- /dev/null
+++ b/war/src/main/java/pnews/servlet/ArticleStore.java
@@ -0,0 +1,36 @@
+package pnews.servlet;
+
+import java.lang.ref.WeakReference;
+import java.util.HashMap;
+
+import pnews.Article;
+
+public class ArticleStore {
+        public final static ArticleStore singleton = new ArticleStore();
+        private final HashMap<String, WeakReference<Article>> articles = new HashMap<>();
+        
+        public Article get(String link) {
+                WeakReference<Article> ref;
+                
+                synchronized (articles) {
+                        ref = articles.get(link);
+                        if (ref == null)
+                                return null;
+                        return ref.get();
+                }
+        }
+        
+        public Article getArticle(String link, ArticleFactory factory) {
+                Article result;
+                
+                synchronized (articles) {
+                        result = get(link);
+                        if (result == null) {
+                                result = factory.create();
+                                articles.put(link, new WeakReference<>(result));
+                        }
+                        
+                        return result;
+                }
+        }
+}
-- 
2.7.4