Ehcache code (#734)

* - 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

spring-all/src/main/java/org/baeldung/ehcache/app/App.java

@@ -0,0 +1,24 @@
+package org.baeldung.ehcache.app;
+
+import org.baeldung.ehcache.calculator.SquaredCalculator;
+import org.baeldung.ehcache.config.CacheHelper;
+
+public class App {
+
+    public static void main(String[] args) {
+
+        SquaredCalculator squaredCalculator = new SquaredCalculator();
+        CacheHelper cacheHelper = new CacheHelper();
+
+        squaredCalculator.setCache(cacheHelper);
+
+        calculate(squaredCalculator);
+        calculate(squaredCalculator);
+    }
+
+    private static void calculate(SquaredCalculator squaredCalculator) {
+        for (int i = 10; i < 15; i++) {
+            System.out.println("Square value of " + i + " is: " + squaredCalculator.getSquareValueOfNumber(i) + "\n");
+        }
+    }
+}

spring-all/src/main/java/org/baeldung/ehcache/calculator/SquaredCalculator.java

@@ -0,0 +1,24 @@
+package org.baeldung.ehcache.calculator;
+
+import org.baeldung.ehcache.config.CacheHelper;
+
+public class SquaredCalculator {
+    private CacheHelper cache;
+
+    public int getSquareValueOfNumber(int input) {
+        if (cache.getSquareNumberCache().containsKey(input)) {
+            return cache.getSquareNumberCache().get(input);
+        }
+
+        System.out.println("Calculating square value of " + input + " and caching result.");
+
+        int squaredValue = (int) Math.pow(input, 2);
+        cache.getSquareNumberCache().put(input, squaredValue);
+
+        return squaredValue;
+    }
+
+    public void setCache(CacheHelper cache) {
+        this.cache = cache;
+    }
+}

spring-all/src/main/java/org/baeldung/ehcache/config/CacheHelper.java

@@ -0,0 +1,25 @@
+package org.baeldung.ehcache.config;
+
+import org.ehcache.Cache;
+import org.ehcache.CacheManager;
+import org.ehcache.config.builders.CacheConfigurationBuilder;
+import org.ehcache.config.builders.CacheManagerBuilder;
+import org.ehcache.config.builders.ResourcePoolsBuilder;
+
+public class CacheHelper {
+
+    private CacheManager cacheManager;
+    private Cache<Integer, Integer> squareNumberCache;
+
+    public CacheHelper() {
+        cacheManager = CacheManagerBuilder.newCacheManagerBuilder().withCache("squaredNumber", CacheConfigurationBuilder.newCacheConfigurationBuilder(Integer.class, Integer.class, ResourcePoolsBuilder.heap(10))).build();
+        cacheManager.init();
+
+        squareNumberCache = cacheManager.getCache("squaredNumber", Integer.class, Integer.class);
+    }
+
+    public Cache<Integer, Integer> getSquareNumberCache() {
+        return squareNumberCache;
+    }
+
+}