Question

Let’s say I have a class in my web app called class ‘Foo’. It has an initialise() method that is called when the bean is created using Spring. The initialise() method then tries to load an external service and assign it to a field. If the service could not be contacted, the field will be set to null.

private Service service;  public void initialise() {     // load external service     // set field to the loaded service if contacted     // set to field to null if service could not be contacted } 

When someone calls the method get() on the class ‘Foo’ the service will be invoked if it was started in the initialise() method. If the field for the service is null, I want to try and load the external service.

public String get() {     if (service == null) {         // try and load the service again     }     // perform operation on the service is service is not null } 

Is it possible that I may have sync issues if I would do something like this?

Answer 1

toolkit‘s answer is correct. To solve the problem, just declare your Foo’s initialise() method to be synchronized. You could refactor Foo as:

private Service service;  public synchronized void initialise() {     if (service == null) {         // load external service         // set field to the loaded service if contacted     } }  public String get() {     if (service == null) {                     initialise(); // try and load the service again     }     // perform operation on the service is service is not null }