Question

I’m just thinking about this. If I have dao bean in spring and that dao bean has a protected/public property “currentSQL”. It will be value in this property “visible” for all concurent requests or not ?

Example:

@Component
public class FooDAO {

  @Autowired
  private DataSource dataSource;

  private String currentSQL;

  public void doSome()
  {
    currentSQL = "Foo SQL query";
   }

  public String getSome()
  {
    return currentSQL;
  }
}

Is currentSQL property in that example above safe per request or not ?

Answer 1

it depends on how you set the scope of FooDAO bean.

<bean id="fooDAO" class="-" scope="prototype"/>

for every access (request) on fooDAO spring creates a new instance of FooDAO. Then it can be considered as Thread-safe, as long as your local threads don’t use the same instance of FooDAO. If it is the case, you have to handle thread access with “public synchronized void doSome()”

<bean id="fooDAO" class="-" scope="singleton"/>

if your bean Singleton, then it’s not thread-safe. The singleton instance is shared among your application. If this is the case, then you have to synchronize the method.