Bael 9411 (#18748)

* BAEL-9411

* BAEL-9411 update the field accessible

---------

Co-authored-by: Wynn Teo <[email protected]>

Author: wynnteo

core-java-modules/core-java-reflection-3/src/main/java/com/baeldung/reflection/stringvalue/DynamicFieldDemo.java

@@ -0,0 +1,5 @@
+package com.baeldung.reflection.stringvalue;
+
+public class DynamicFieldDemo {
+    public String title = "Dynamic Access";
+}

core-java-modules/core-java-reflection-3/src/main/java/com/baeldung/reflection/stringvalue/PrivateFieldDemo.java

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+package com.baeldung.reflection.stringvalue;
+
+public class PrivateFieldDemo {
+    private String secret = "Hidden Value";
+}

core-java-modules/core-java-reflection-3/src/main/java/com/baeldung/reflection/stringvalue/PublicFieldDemo.java

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+package com.baeldung.reflection.stringvalue;
+
+public class PublicFieldDemo {
+    public String name = "Baeldung";
+}

core-java-modules/core-java-reflection-3/src/main/java/com/baeldung/reflection/stringvalue/User.java

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+package com.baeldung.reflection.stringvalue;
+
+public class User {
+    private String username = "baeldung_user";
+}

core-java-modules/core-java-reflection-3/src/test/java/com/baeldung/reflection/stringvalue/StringValueReflectionUnitTest.java

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+package com.baeldung.reflection.stringvalue;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.lang.reflect.Field;
+import java.util.Objects;
+
+import org.junit.jupiter.api.Test;
+
+public class StringValueReflectionUnitTest {
+
+    @Test
+    void givenPublicStringField_whenAccessWithReflection_thenReturnValue() throws Exception {
+        PublicFieldDemo example = new PublicFieldDemo();
+        Field field = PublicFieldDemo.class.getField("name");
+        String value = (String) field.get(example);
+        assertEquals("Baeldung", value);
+    }
+
+    @Test
+    void givenPrivateStringField_whenAccessWithReflection_thenReturnValue() throws Exception {
+        PrivateFieldDemo example = new PrivateFieldDemo();
+        Field field = PrivateFieldDemo.class.getDeclaredField("secret");
+        field.setAccessible(true);
+        String value = (String) field.get(example);
+        assertEquals("Hidden Value", value);
+    }
+
+    @Test
+    void givenFieldNameVariable_whenAccessWithReflection_thenReturnValue() throws Exception {
+        DynamicFieldDemo example = new DynamicFieldDemo();
+        String fieldName = "title";
+        Field field = DynamicFieldDemo.class.getField(fieldName);
+        String value = (String) field.get(example);
+        assertEquals("Dynamic Access", value);
+    }
+
+    public static String getFieldValueAsString(Object obj, String fieldName) throws Exception {
+        Field field = obj.getClass().getDeclaredField(fieldName);
+        boolean accessible = field.canAccess(obj);
+
+        try {
+            if (!accessible) {
+                field.setAccessible(true);
+            }
+            return Objects.toString(field.get(obj), null);
+        } finally {
+            if (!accessible) {
+                field.setAccessible(false);
+            }
+        }
+    }
+
+    @Test
+    void givenObjectAndFieldName_whenUseUtilityMethod_thenReturnStringValue() throws Exception {
+        User user = new User();
+        String value = getFieldValueAsString(user, "username");
+        assertEquals("baeldung_user", value);
+    }
+}