service locator pattern

core-java/src/main/java/com/baeldung/designpatterns/service/locator/Cache.java

@@ -0,0 +1,39 @@
+package com.baeldung.designpatterns.service.locator;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class Cache {
+    private List<MessagingService> services;
+
+    public Cache(){
+        services = new ArrayList<MessagingService>();
+    }
+
+    public MessagingService getService(String serviceName){
+
+        for (MessagingService service : services) {
+            if(service.getServiceName().equalsIgnoreCase(serviceName)){
+                System.out.println("Returning cached  " + serviceName + " object");
+                return service;
+            }
+        }
+        return null;
+    }
+
+    public void addService(MessagingService newService){
+        boolean exists = false;
+
+        for (MessagingService service : services) {
+            if(service.getServiceName().equalsIgnoreCase(newService.getServiceName())){
+                exists = true;
+            }
+        }
+        if(!exists){
+            services.add(newService);
+        }
+    }
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/EmailService.java

@@ -0,0 +1,15 @@
+package com.baeldung.designpatterns.service.locator;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class EmailService implements MessagingService {
+
+    public String getMessageBody() {
+        return "email message";
+    }
+
+    public String getServiceName() {
+        return "EmailService";
+    }
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/InitialContext.java

@@ -0,0 +1,17 @@
+package com.baeldung.designpatterns.service.locator;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class InitialContext {
+
+    public Object lookup(String jndiName) {
+
+        if (jndiName.equalsIgnoreCase("EmailService")) {
+            return new EmailService();
+        } else if (jndiName.equalsIgnoreCase("SMSService")) {
+            return new SMSService();
+        }
+        return null;
+    }
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/Main.java

@@ -0,0 +1,12 @@
+package com.baeldung.designpatterns.service.locator;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        MessagingService service = ServiceLocator.getService("EmailService");
+        service.getMessageBody();
+    }
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/MessagingService.java

@@ -0,0 +1,8 @@
+package com.baeldung.designpatterns.service.locator;
+
+public interface MessagingService {
+
+    String getMessageBody();
+
+    String getServiceName();
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/SMSService.java

@@ -0,0 +1,15 @@
+package com.baeldung.designpatterns.service.locator;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class SMSService implements MessagingService {
+
+    public String getMessageBody() {
+        return "sms message";
+    }
+
+    public String getServiceName() {
+        return "SMSService";
+    }
+}

core-java/src/main/java/com/baeldung/designpatterns/service/locator/ServiceLocator.java

@@ -0,0 +1,26 @@
+package com.baeldung.designpatterns.service.locator;
+
+/**
+ * Created by Gebruiker on 4/20/2018.
+ */
+public class ServiceLocator {
+    private static Cache cache;
+
+    static {
+        cache = new Cache();
+    }
+
+    public static MessagingService getService(String jndiName){
+
+        MessagingService service = cache.getService(jndiName);
+
+        if(service != null){
+            return service;
+        }
+
+        InitialContext context = new InitialContext();
+        MessagingService service1 = (MessagingService)context.lookup(jndiName);
+        cache.addService(service1);
+        return service1;
+    }
+}