Example - 1

In the following Java example a Customer Entity EJB provides access to customer information in a database for a business application.

private String id;private String firstName;private String lastName;private Address address;public Customer() {...}public Customer(String id, String firstName, String lastName) {...}@Idpublic String getCustomerId() {...}public synchronized void setCustomerId(String id) {...}public String getFirstName() {...}public synchronized void setFirstName(String firstName) {...}public String getLastName() {...}public synchronized void setLastName(String lastName) {...}@OneToOne()public Address getAddress() {...}public synchronized void setAddress(Address address) {...}@Entitypublic class Customer implements Serializable {}

However, the customer entity EJB uses the synchronized keyword for the set methods to attempt to provide thread safe synchronization for the member variables. The use of synchronized methods violate the restriction of the EJB specification against the use synchronization primitives within EJBs. Using synchronization primitives may cause inconsistent behavior of the EJB when used within different EJB containers.