fix: Use WeakHashMap for caching proxy classes

src/main/java/io/appium/java_client/proxy/Helpers.java

@@ -16,7 +16,10 @@
 
 package io.appium.java_client.proxy;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
+import java.util.Map;
+import java.util.WeakHashMap;
 import lombok.Value;
 import net.bytebuddy.ByteBuddy;
 import net.bytebuddy.description.method.MethodDescription;
@@ -32,14 +35,15 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static java.util.Objects.requireNonNull;
 import static net.bytebuddy.matcher.ElementMatchers.namedOneOf;
 
+/**
+ * The type Helpers.
+ */
 public class Helpers {
     public static final Set<String> OBJECT_METHOD_NAMES = Stream.of(Object.class.getMethods())
             .map(Method::getName)
@@ -50,7 +54,18 @@ public class Helpers {
     // the performance and to avoid extensive memory usage for our case, where
     // the amount of instrumented proxy classes we create is low in comparison to the amount
     // of proxy instances.
-    private static final ConcurrentMap<ProxyClassSignature, Class<?>> CACHED_PROXY_CLASSES = new ConcurrentHashMap<>();
+    private static final Map<ProxyClassSignature, Class<?>> CACHED_PROXY_CLASSES = Collections.synchronizedMap(new WeakHashMap<>());
+
+    /**
+     * Gets CACHED_PROXY_CLASSES size.
+     * Used for cache clear up tests {@see io.appium.java_client.pagefactory_tests.widget.tests.combined.CombinedWidgetTest}.
+     *
+     * @return the cached proxy classes size
+     */
+    @VisibleForTesting
+    public static int getCachedProxyClassesSize() {
+        return CACHED_PROXY_CLASSES.size();
+    }
 
     private Helpers() {
     }

src/test/java/io/appium/java_client/pagefactory_tests/widget/tests/combined/CombinedWidgetTest.java

@@ -6,6 +6,7 @@
 import io.appium.java_client.pagefactory_tests.widget.tests.AbstractStubWebDriver;
 import io.appium.java_client.pagefactory_tests.widget.tests.DefaultStubWidget;
 import io.appium.java_client.pagefactory_tests.widget.tests.android.DefaultAndroidWidget;
+import io.appium.java_client.proxy.Helpers;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
@@ -20,6 +21,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.lessThan;
 import static org.openqa.selenium.support.PageFactory.initElements;
 
 
@@ -57,6 +59,7 @@ public static Stream<Arguments> data() {
     @ParameterizedTest
     @MethodSource("data")
     void checkThatWidgetsAreCreatedCorrectly(AbstractApp app, WebDriver driver, Class<?> widgetClass) {
+        assertProxyClassCacheGrowth();
         initElements(new AppiumFieldDecorator(driver), app);
         assertThat("Expected widget class was " + widgetClass.getName(),
                 app.getWidget().getSubWidget().getSelfReference().getClass(),
@@ -161,4 +164,22 @@ public List<PartiallyCombinedWidget> getWidgets() {
             return multipleWidgets;
         }
     }
+
+
+    /**
+     * Assert proxy class cache growth for this test class.
+     * The (@link io.appium.java_client.proxy.Helpers#CACHED_PROXY_CLASSES) should be populated during these tests.
+     * Prior to the Caching issue being resolved
+     * - the CACHED_PROXY_CLASSES would grow indefinitely, resulting in an Out Of Memory exception.
+     * - this ParameterizedTest would have the CACHED_PROXY_CLASSES grow to 266 entries.
+     */
+    private void assertProxyClassCacheGrowth() {
+        System.gc(); //Trying to force a collection for more accurate check numbers
+        int thresholdSize = 50;
+        assertThat(
+            "Proxy Class Cache threshold is " + thresholdSize,
+            Helpers.getCachedProxyClassesSize(),
+            lessThan(thresholdSize)
+        );
+    }
 }