Use jackson's TypeReference to deserialize into generic classes without warnings

Author: TheMythologist

src/main/java/seedu/address/commons/util/ConfigUtil.java

@@ -4,6 +4,8 @@
 import java.nio.file.Path;
 import java.util.Optional;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import seedu.address.commons.core.Config;
 import seedu.address.commons.exceptions.DataLoadingException;
 
@@ -13,7 +15,7 @@
 public class ConfigUtil {
 
     public static Optional<Config> readConfig(Path configFilePath) throws DataLoadingException {
-        return JsonUtil.readJsonFile(configFilePath, Config.class);
+        return JsonUtil.readJsonFile(configFilePath, new TypeReference<Config>() {});
     }
 
     public static void saveConfig(Config config, Path configFilePath) throws IOException {

src/main/java/seedu/address/commons/util/JsonUtil.java

@@ -12,6 +12,7 @@
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -43,21 +44,21 @@ static <T> void serializeObjectToJsonFile(Path jsonFile, T objectToSerialize) th
         FileUtil.writeToFile(jsonFile, toJsonString(objectToSerialize));
     }
 
-    static <T> T deserializeObjectFromJsonFile(Path jsonFile, Class<T> classOfObjectToDeserialize)
+    static <T> T deserializeObjectFromJsonFile(Path jsonFile, TypeReference<T> typeRef)
             throws IOException {
-        return fromJsonString(FileUtil.readFromFile(jsonFile), classOfObjectToDeserialize);
+        return fromJsonString(FileUtil.readFromFile(jsonFile), typeRef);
     }
 
     /**
      * Returns the JSON object from the given file or {@code Optional.empty()} object if the file is not found.
      * If any values are missing from the file, default values will be used, as long as the file is a valid JSON file.
      *
      * @param filePath cannot be null.
-     * @param classOfObjectToDeserialize JSON file has to correspond to the structure in the class given here.
+     * @param typeRef JSON file has to correspond to the structure in the {@oode TypeReference} given here.
      * @throws DataLoadingException if loading of the JSON file failed.
      */
     public static <T> Optional<T> readJsonFile(
-            Path filePath, Class<T> classOfObjectToDeserialize) throws DataLoadingException {
+            Path filePath, TypeReference<T> typeRef) throws DataLoadingException {
         requireNonNull(filePath);
 
         if (!Files.exists(filePath)) {
@@ -68,7 +69,7 @@ public static <T> Optional<T> readJsonFile(
         T jsonFile;
 
         try {
-            jsonFile = deserializeObjectFromJsonFile(filePath, classOfObjectToDeserialize);
+            jsonFile = deserializeObjectFromJsonFile(filePath, typeRef);
         } catch (IOException e) {
             logger.warning("Error reading from jsonFile file " + filePath + ": " + e);
             throw new DataLoadingException(e);
@@ -97,8 +98,8 @@ public static <T> void saveJsonFile(T jsonFile, Path filePath) throws IOExceptio
      * @param <T> The generic type to create an instance of
      * @return The instance of T with the specified values in the JSON string
      */
-    public static <T> T fromJsonString(String json, Class<T> instanceClass) throws IOException {
-        return objectMapper.readValue(json, instanceClass);
+    public static <T> T fromJsonString(String json, TypeReference<T> typeRef) throws IOException {
+        return objectMapper.readValue(json, typeRef);
     }
 
     /**

src/main/java/seedu/address/storage/JsonAddressBookStorage.java

@@ -7,6 +7,8 @@
 import java.util.Optional;
 import java.util.logging.Logger;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import seedu.address.commons.core.LogsCenter;
 import seedu.address.commons.exceptions.DataLoadingException;
 import seedu.address.commons.exceptions.IllegalValueException;
@@ -46,7 +48,7 @@ public Optional<ReadOnlyAddressBook> readAddressBook(Path filePath) throws DataL
         requireNonNull(filePath);
 
         Optional<JsonSerializableAddressBook> jsonAddressBook = JsonUtil.readJsonFile(
-                filePath, JsonSerializableAddressBook.class);
+                filePath, new TypeReference<JsonSerializableAddressBook>() {});
         if (!jsonAddressBook.isPresent()) {
             return Optional.empty();
         }

src/main/java/seedu/address/storage/JsonUserPrefsStorage.java

@@ -4,6 +4,8 @@
 import java.nio.file.Path;
 import java.util.Optional;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import seedu.address.commons.exceptions.DataLoadingException;
 import seedu.address.commons.util.JsonUtil;
 import seedu.address.model.ReadOnlyUserPrefs;
@@ -36,7 +38,7 @@ public Optional<UserPrefs> readUserPrefs() throws DataLoadingException {
      * @throws DataLoadingException if the file format is not as expected.
      */
     public Optional<UserPrefs> readUserPrefs(Path prefsFilePath) throws DataLoadingException {
-        return JsonUtil.readJsonFile(prefsFilePath, UserPrefs.class);
+        return JsonUtil.readJsonFile(prefsFilePath, new TypeReference<UserPrefs>() {});
     }
 
     @Override

src/test/java/seedu/address/commons/util/JsonUtilTest.java

@@ -7,6 +7,8 @@
 
 import org.junit.jupiter.api.Test;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import seedu.address.testutil.SerializableTestClass;
 import seedu.address.testutil.TestUtil;
 
@@ -32,7 +34,7 @@ public void deserializeObjectFromJsonFile_noExceptionThrown() throws IOException
         FileUtil.writeToFile(SERIALIZATION_FILE, SerializableTestClass.JSON_STRING_REPRESENTATION);
 
         SerializableTestClass serializableTestClass = JsonUtil
-                .deserializeObjectFromJsonFile(SERIALIZATION_FILE, SerializableTestClass.class);
+                .deserializeObjectFromJsonFile(SERIALIZATION_FILE, new TypeReference<SerializableTestClass>() {});
 
         assertEquals(serializableTestClass.getName(), SerializableTestClass.getNameTestValue());
         assertEquals(serializableTestClass.getListOfLocalDateTimes(), SerializableTestClass.getListTestValues());

src/test/java/seedu/address/storage/JsonSerializableAddressBookTest.java

@@ -8,6 +8,8 @@
 
 import org.junit.jupiter.api.Test;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import seedu.address.commons.exceptions.IllegalValueException;
 import seedu.address.commons.util.JsonUtil;
 import seedu.address.model.AddressBook;
@@ -23,7 +25,7 @@ public class JsonSerializableAddressBookTest {
     @Test
     public void toModelType_typicalPersonsFile_success() throws Exception {
         JsonSerializableAddressBook dataFromFile = JsonUtil.readJsonFile(TYPICAL_PERSONS_FILE,
-                JsonSerializableAddressBook.class).get();
+                new TypeReference<JsonSerializableAddressBook>() {}).get();
         AddressBook addressBookFromFile = dataFromFile.toModelType();
         AddressBook typicalPersonsAddressBook = TypicalPersons.getTypicalAddressBook();
         assertEquals(addressBookFromFile, typicalPersonsAddressBook);
@@ -32,14 +34,14 @@ public void toModelType_typicalPersonsFile_success() throws Exception {
     @Test
     public void toModelType_invalidPersonFile_throwsIllegalValueException() throws Exception {
         JsonSerializableAddressBook dataFromFile = JsonUtil.readJsonFile(INVALID_PERSON_FILE,
-                JsonSerializableAddressBook.class).get();
+                new TypeReference<JsonSerializableAddressBook>() {}).get();
         assertThrows(IllegalValueException.class, dataFromFile::toModelType);
     }
 
     @Test
     public void toModelType_duplicatePersons_throwsIllegalValueException() throws Exception {
         JsonSerializableAddressBook dataFromFile = JsonUtil.readJsonFile(DUPLICATE_PERSON_FILE,
-                JsonSerializableAddressBook.class).get();
+                new TypeReference<JsonSerializableAddressBook>() {}).get();
         assertThrows(IllegalValueException.class, JsonSerializableAddressBook.MESSAGE_DUPLICATE_PERSON,
                 dataFromFile::toModelType);
     }