war/src/main/java/pnews/servlet/ArticleStore.java

   1 package pnews.servlet;
   2
   3 import java.lang.ref.WeakReference;
   4 import java.util.ArrayList;
   5 import java.util.HashMap;
   6 import java.util.logging.Logger;
   7
   8 import pnews.Article;
   9
  10 public class ArticleStore {
  11         public final static ArticleStore singleton = new ArticleStore();
  12         private final HashMap<String, WeakReference<Article>> articles = new HashMap<>();
  13         private final static Logger LOG = Logger.getLogger(ArticleStore.class.getName());
  14
  15         public Article get(String link) {
  16                 WeakReference<Article> ref;
  17                 Article result;
  18
  19                 synchronized (articles) {
  20                         ref = articles.get(link);
  21                         if (ref == null) {
  22                                 return null;
  23                         }
  24
  25                         result = ref.get();
  26                         if (result == null) {
  27                                 LOG.info("Article has been released from memory: " + link);
  28                                 articles.remove(link);
  29                         }
  30
  31                         return result;
  32                 }
  33         }
  34
  35         public Article getArticle(String link, ArticleFactory factory) {
  36                 Article result;
  37
  38                 synchronized (articles) {
  39                         result = get(link);
  40                         if (result == null) {
  41                                 result = factory.create();
  42                                 articles.put(link, new WeakReference<>(result));
  43                                 LOG.info("Article has been added: " + result.link);
  44                         }
  45
  46                         return result;
  47                 }
  48         }
  49
  50         public long size() {
  51                 synchronized (this) {
  52                         return articles.size();
  53                 }
  54         }
  55
  56         public Article[] getArticles() {
  57                 ArrayList<Article> result;
  58                 Article a;
  59
  60                 synchronized (articles) {
  61                         result = new ArrayList<>(articles.size());
  62
  63                         for (WeakReference<Article> r: articles.values()) {
  64                                 a = r.get();
  65                                 if (a != null)
  66                                         result.add(a);
  67                         }
  68
  69                         return result.toArray(new Article[] {});
  70                 }
  71         }
  72 }