Add reflection utils

Author: xxlabaza

src/main/java/io/appulse/utils/ReflectionUtils.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.appulse.utils;
+
+import static java.util.Optional.empty;
+import static java.util.Optional.ofNullable;
+
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.Optional;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+
+import lombok.NonNull;
+import lombok.SneakyThrows;
+import lombok.val;
+
+/**
+ * Different reflection helpers.
+ *
+ * @author Artem Labazin
+ * @since 1.0.1
+ */
+public final class ReflectionUtils {
+
+  /**
+   * Extracts field value from object by its name.
+   *
+   * @param obj  object, from which need to extract field's value.
+   * @param name field's name
+   *
+   * @return optional - field's value or nothing.
+   */
+  @SneakyThrows
+  public static Optional<Object> getFieldValueFrom (@NonNull Object obj, @NonNull String name) {
+    val optional = findIn(obj, Class::getDeclaredFields, field -> field.getName().equals(name));
+    if (optional.isPresent()) {
+      val field = optional.get();
+      AccessController.doPrivileged(new PrivilegedAction<Object>() {
+
+        @Override
+        public Object run () {
+          field.setAccessible(true);
+          return null;
+        }
+      });
+      val value = field.get(obj);
+      return ofNullable(value);
+    }
+    return empty();
+  }
+
+  /**
+   * Invoke method of object with specified arguments.
+   *
+   * @param obj     object
+   * @param name    method's name
+   * @param arguments optional arguments for method
+   *
+   * @return method's invocation result.
+   */
+  @SneakyThrows
+  public static Object invokeMethodOf (@NonNull Object obj, @NonNull String name, Object... arguments) {
+    val optional = findIn(obj, Class::getDeclaredMethods, method -> method.getName().equals(name));
+    if (optional.isPresent()) {
+      val method = optional.get();
+      return method.invoke(obj, arguments);
+    }
+    return null;
+  }
+
+  // Searches method/field in object by predicate.
+  private static <T> Optional<T> findIn (Object obj, Function<Class<?>, T[]> extractor, Predicate<T> predicate) {
+    Class<?> current = obj.getClass();
+
+    while (current != null) {
+      val values = extractor.apply(current);
+      val optional = Stream.of(values)
+          .filter(predicate)
+          .findFirst();
+
+      if (optional.isPresent()) {
+        return optional;
+      }
+      current = current.getSuperclass();
+    }
+    return empty();
+  }
+
+  private ReflectionUtils () {
+  }
+}

src/test/java/io/appulse/utils/ReflectionUtilsTest.java

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.appulse.utils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+import lombok.Setter;
+import org.junit.Test;
+
+/**
+ *
+ * @author Artem Labazin
+ */
+public class ReflectionUtilsTest {
+
+    @Test
+    public void getFieldValueFrom () {
+        ChildClass object = new ChildClass("Artem", 27);
+
+        assertThat(ReflectionUtils.getFieldValueFrom(object, "name"))
+                .isPresent()
+                .hasValue("Artem");
+
+        assertThat(ReflectionUtils.getFieldValueFrom(object, "age"))
+                .isPresent()
+                .hasValue(27);
+
+        assertThat(ReflectionUtils.getFieldValueFrom(object, "popa"))
+                .isNotPresent();
+    }
+
+    @Test
+    public void invokeMethodOf () {
+        ChildClass object = new ChildClass("Artem", 27);
+
+        assertThat(ReflectionUtils.invokeMethodOf(object, "getName"))
+                .isNotNull()
+                .isEqualTo("Artem");
+
+        assertThat(ReflectionUtils.invokeMethodOf(object, "getAge"))
+                .isNotNull()
+                .isEqualTo(27);
+
+        assertThat(object.isFlag()).isFalse();
+        assertThat(ReflectionUtils.invokeMethodOf(object, "setFlag", true))
+                .isNull();
+        assertThat(object.isFlag()).isTrue();
+
+        assertThat(ReflectionUtils.invokeMethodOf(object, "popa"))
+                .isNull();
+    }
+
+    @Getter
+    @RequiredArgsConstructor
+    class ParentClass {
+
+        private final int age;
+    }
+
+    @Getter
+    class ChildClass extends ParentClass {
+
+        private final String name;
+
+        @Setter
+        private boolean flag;
+
+        ChildClass (String name, int age) {
+            super(age);
+            this.name = name;
+        }
+    }
+}