🏷 Jakarta EE
5 patterns
Topic: Jakarta EE
All Java patterns related to Jakarta EE — java.evolved
Enterprise
EJB Timer vs Jakarta Scheduler
Old
@Stateless
public class ReportGenerator {
@Resource
TimerService timerService;
@PostConstruct
public void init() {
timerService.createCalendarTimer(
new ScheduleExpression()
.hour("2").minute("0"));
}
@Timeout
public void generateReport(Timer timer) {
// runs every day at 02:00
buildDailyReport();
}
}
Modern
@ApplicationScoped
public class ReportGenerator {
@Resource
ManagedScheduledExecutorService scheduler;
@PostConstruct
public void init() {
scheduler.scheduleAtFixedRate(
this::generateReport,
0, 24, TimeUnit.HOURS);
}
public void generateReport() {
buildDailyReport();
}
}
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JDK 11+
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Enterprise
EJB versus CDI
Old
@Stateless
public class OrderEJB {
@EJB
private InventoryEJB inventory;
public void placeOrder(Order order) {
// container-managed transaction
inventory.reserve(order.getItem());
}
}
Modern
@ApplicationScoped
public class OrderService {
@Inject
private InventoryService inventory;
@Transactional
public void placeOrder(Order order) {
inventory.reserve(order.getItem());
}
}
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JDK 11+
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Enterprise
JNDI Lookup vs CDI Injection
Old
public class OrderService {
private DataSource ds;
public void init() throws NamingException {
InitialContext ctx = new InitialContext();
ds = (DataSource) ctx.lookup(
"java:comp/env/jdbc/OrderDB");
}
public List<Order> findAll()
throws SQLException {
try (Connection con = ds.getConnection()) {
// query orders
}
}
}
Modern
@ApplicationScoped
public class OrderService {
@Inject
@Resource(name = "jdbc/OrderDB")
DataSource ds;
public List<Order> findAll()
throws SQLException {
try (Connection con = ds.getConnection()) {
// query orders
}
}
}
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JDK 11+
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Enterprise
JSF Managed Bean vs CDI Named Bean
Old
@ManagedBean
@SessionScoped
public class UserBean implements Serializable {
@ManagedProperty("#{userService}")
private UserService userService;
private String name;
public String getName() { return name; }
public void setName(String name) {
this.name = name;
}
public void setUserService(UserService svc) {
this.userService = svc;
}
}
Modern
@Named
@SessionScoped
public class UserBean implements Serializable {
@Inject
private UserService userService;
private String name;
public String getName() { return name; }
public void setName(String name) {
this.name = name;
}
}
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JDK 11+
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Enterprise
Singleton EJB vs CDI @ApplicationScoped
Old
@Singleton
@Startup
@ConcurrencyManagement(
ConcurrencyManagementType.CONTAINER)
public class ConfigCache {
private Map<String, String> cache;
@PostConstruct
public void load() {
cache = loadFromDatabase();
}
@Lock(LockType.READ)
public String get(String key) {
return cache.get(key);
}
@Lock(LockType.WRITE)
public void refresh() {
cache = loadFromDatabase();
}
}
Modern
@ApplicationScoped
public class ConfigCache {
private volatile Map<String, String> cache;
@PostConstruct
public void load() {
cache = loadFromDatabase();
}
public String get(String key) {
return cache.get(key);
}
public void refresh() {
cache = loadFromDatabase();
}
}
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JDK 11+
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