Difference between CDI and EJB singleton (#6915)

* Singleton injection examples and tests added * code and tests implemented
2019-05-08 16:40:54 +02:00
parent 57ec69ad3b
commit 8209ec4a1f
5 changed files with 286 additions and 0 deletions
@@ -0,0 +1,28 @@
+package com.baeldung.singleton;
+
+public class Car {
+    
+    private String type;
+    private String model;
+    private boolean serviced = false;
+    
+    public Car(String type, String model) {
+        super();
+        this.type = type;
+        this.model = model;
+    }
+
+    public boolean isServiced () {
+        return serviced;
+    }
+    
+    public void setServiced(Boolean serviced) {
+        this.serviced = serviced;
+    }
+
+    @Override
+    public String toString() {
+        return "Car [type=" + type + ", model=" + model + "]";
+    }
+    
+}
@@ -0,0 +1,23 @@
+package com.baeldung.singleton;
+
+import java.util.UUID;
+
+import javax.enterprise.context.Dependent;
+
+import org.springframework.web.context.annotation.RequestScope;
+
+@RequestScope
+public class CarServiceBean {
+
+    private UUID id = UUID.randomUUID();
+
+    public UUID getId() {
+        return this.id;
+    }
+
+    @Override
+    public String toString() {
+        return "CarService [id=" + id + "]";
+    }
+
+}
@@ -0,0 +1,46 @@
+package com.baeldung.singleton;
+
+import java.util.UUID;
+
+import javax.ejb.Singleton;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Singleton
+public class CarServiceEjbSingleton {
+
+    private static Logger LOG = LoggerFactory.getLogger(CarServiceEjbSingleton.class);
+
+    private UUID id = UUID.randomUUID();
+
+    private static int serviceQueue;
+
+    public UUID getId() {
+        return this.id;
+    }
+
+    @Override
+    public String toString() {
+        return "CarServiceEjbSingleton [id=" + id + "]";
+    }
+
+    public int service(Car car) {
+        serviceQueue++;
+        LOG.info("Car {} is being serviced @ CarServiceEjbSingleton - serviceQueue: {}", car, serviceQueue);
+        simulateService(car);
+        serviceQueue--;
+        LOG.info("Car service for {} is completed - serviceQueue: {}", car, serviceQueue);
+        return serviceQueue;
+    }
+    
+    private void simulateService(Car car) {
+        try {
+            Thread.sleep(100);
+            car.setServiced(true);
+        } catch (InterruptedException e) {
+            LOG.error("CarServiceEjbSingleton::InterruptedException: {}", e);
+        }
+    }
+
+}
@@ -0,0 +1,47 @@
+package com.baeldung.singleton;
+
+import java.util.UUID;
+
+import javax.inject.Singleton;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Singleton
+public class CarServiceSingleton {
+
+    private static Logger LOG = LoggerFactory.getLogger(CarServiceSingleton.class);
+
+    private UUID id = UUID.randomUUID();
+
+    private static int serviceQueue;
+
+    public UUID getId() {
+        return this.id;
+    }
+
+    @Override
+    public String toString() {
+        return "CarServiceSingleton [id=" + id + "]";
+    }
+
+    public int service(Car car) {
+        serviceQueue++;
+        LOG.info("Car {} is being serviced @ CarServiceSingleton - serviceQueue: {}", car, serviceQueue);
+        simulateService(car);
+        serviceQueue--;
+        LOG.info("Car service for {} is completed - serviceQueue: {}", car, serviceQueue);
+        return serviceQueue;
+
+    }
+
+    private void simulateService(Car car) {
+        try {
+            Thread.sleep(100);
+            car.setServiced(true);
+        } catch (InterruptedException e) {
+            LOG.error("CarServiceSingleton::InterruptedException: {}", e);
+        }
+    }
+
+}