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PObest practice for thread safe session bean in spring?
 

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  1. PObest practice for thread safe session bean in spring?
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    <p>I'm wondering what is the best practice for making a session bean thread safe.</p> <p>Let's assume I have this session bean and its service:</p> <pre><code>@Component @Scope(value = WebApplicationContext.SCOPE_SESSION, proxyMode = ScopedProxyMode.TARGET_CLASS) class Cart { private HashSet&lt;Item&gt; items = new HashSet&lt;Item&gt;(); private int counter = 0; public HashSet&lt;Item&gt; getItems() { return items; } public int getCounter() { return counter; } } @Service class CartService { @Autowired private Cart cart; public void addItem(Item item) throws FullException { if (cart.getCounter() &gt; 1234) { throw new FullException(); } cart.getItems().add(item); } } </code></pre> <p>The code above is not thread safe and will cause issues when multiple threads (of the same session, eg. by asynchronous Ajax-requests) perform a <code>CartService.addItem(Item)</code>.</p> <p>I think I'm not the first with this problem, but my researches didn't bring me to a best practice.</p> <p>The worst thing I could do would synchronize addItem() as CartService is shared by multiple sessions. Synchronizing on cart in <code>CartService.addItem()</code> seems to me similarly bad, as Cart is a proxied bean. Which I understand as all sessions would still synchronize on the same object.</p> <p>One acceptable solution seems to be a synchronized block on <code>Cart.getItems()</code> in <code>CartService.addItem()</code>:</p> <pre><code>@Service class CartService { @Autowired private Cart cart; public void addItem(Item item) { synchronized(cart.getItems()) { if (cart.getCounter() &gt; 1234) { throw new FullException(); } cart.getItems().add(item); } } } </code></pre> <p>Is there any best practice? Maybe spring has something to offer for this problem?</p>
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