Ehcache article source code (#751)

* - created packages for each logical part of application
- created validator for WebsiteUser rest API
- created ValidatorEventRegister class which fixes known bug for not
detecting generated events
- created custom Exception Handler which creates better response
messages

* Code formatting

* formated pom.xml
replaced for loops with streams
fixed bug while getting all beans

* removed unnecessary code
changed repository type

* - added test for Spring Data REST APIs
- changed bad request return code
- formated code

* - added source code for ehcache article
- added ehcache dependency to pom.xml

* - added test for ehcache article
- removed main method which was only for testing purposes

spring-all/src/test/java/org/baeldung/ehcache/SquareCalculatorTest.java

@@ -0,0 +1,43 @@
+package org.baeldung.ehcache;
+
+import static org.junit.Assert.*;
+
+import org.baeldung.ehcache.calculator.SquaredCalculator;
+import org.baeldung.ehcache.config.CacheHelper;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SquareCalculatorTest {
+    SquaredCalculator squaredCalculator = new SquaredCalculator();
+    CacheHelper cacheHelper = new CacheHelper();
+
+    @Before
+    public void setup() {
+        squaredCalculator.setCache(cacheHelper);
+
+    }
+
+    @Test
+    public void whenCalculatingSquareValueOnce_thenCacheDontHaveValues() {
+        for (int i = 10; i < 15; i++) {
+            assertFalse(cacheHelper.getSquareNumberCache().containsKey(i));
+            System.out.println("Square value of " + i + " is: "
+                    + squaredCalculator.getSquareValueOfNumber(i) + "\n");
+        }
+    }
+
+    @Test
+    public void whenCalculatingSquareValueAgain_thenCacheHasAllValues() {
+        for (int i = 10; i < 15; i++) {
+            assertFalse(cacheHelper.getSquareNumberCache().containsKey(i));
+            System.out.println("Square value of " + i + " is: "
+                    + squaredCalculator.getSquareValueOfNumber(i) + "\n");
+        }
+        
+        for (int i = 10; i < 15; i++) {
+            assertTrue(cacheHelper.getSquareNumberCache().containsKey(i));
+            System.out.println("Square value of " + i + " is: "
+                    + squaredCalculator.getSquareValueOfNumber(i) + "\n");
+        }
+    }
+}