Json Array to Java List

Author: lokeshgupta1981

pom.xml

@@ -117,6 +117,11 @@
       <artifactId>gson</artifactId>
       <version>2.10.1</version>
     </dependency>
+    <dependency>
+      <groupId>org.json</groupId>
+      <artifactId>json</artifactId>
+      <version>20230227</version>
+    </dependency>
     <dependency>
       <groupId>org.apache.commons</groupId>
       <artifactId>commons-compress</artifactId>

src/main/java/com/howtodoinjava/DoNotCommit.java

@@ -0,0 +1,91 @@
+package com.howtodoinjava.json;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.reflect.TypeToken;
+import com.google.gson.Gson;
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.json.JSONArray;
+import org.json.JSONObject;
+import org.junit.jupiter.api.Assertions;
+
+public class JsonArrayToList {
+
+  public static void main(String[] args) throws IOException, URISyntaxException {
+
+    URL fileUrl = JsonArrayToList.class.getClassLoader().getResource("data.json");
+    Path filePath = Paths.get(fileUrl.toURI());
+    String jsonArray = Files.readString(filePath);
+
+    System.out.println(jsonArray);
+
+    usingJson(jsonArray);
+    usingGson(jsonArray);
+    usingJackson(jsonArray);
+  }
+
+  static void usingJson(String json) {
+    JSONArray jsonArray = new JSONArray(json);
+    List<Person> arrayList = new ArrayList<>();
+
+    for (int i = 0; i < jsonArray.length(); i++) {
+
+      JSONObject jsonPerson = jsonArray.getJSONObject(i);
+
+      long id = jsonPerson.getLong("id");
+      String name = jsonPerson.getString("name");
+      int age = jsonPerson.getInt("age");
+
+      Person person = new Person(id, name, age);
+      arrayList.add(person);
+    }
+
+    Assertions.assertEquals(3, arrayList.size());
+    Assertions.assertEquals(1, arrayList.get(0).getId());
+    Assertions.assertEquals("Alex", arrayList.get(0).getName());
+    Assertions.assertEquals(41, arrayList.get(0).getAge());
+  }
+
+  static void usingGson(String jsonArray) {
+    Gson gson = new Gson();
+    Type listType = new TypeToken<List<Person>>() {}.getType();
+
+    List<Person> gsonList = gson.fromJson(jsonArray, listType);
+    Assertions.assertEquals(3, gsonList.size());
+    Assertions.assertEquals(1, gsonList.get(0).getId());
+    Assertions.assertEquals("Alex", gsonList.get(0).getName());
+    Assertions.assertEquals(41, gsonList.get(0).getAge());
+  }
+
+  static void usingJackson(String jsonArray) throws JsonProcessingException {
+    ObjectMapper objectMapper = new ObjectMapper();
+    TypeReference<List<Person>> jacksonTypeReference = new TypeReference<>() {};
+
+    List<Person> jacksonList = objectMapper.readValue(jsonArray, jacksonTypeReference);
+    Assertions.assertEquals(3, jacksonList.size());
+    Assertions.assertEquals(1, jacksonList.get(0).getId());
+    Assertions.assertEquals("Alex", jacksonList.get(0).getName());
+    Assertions.assertEquals(41, jacksonList.get(0).getAge());
+  }
+}
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+class Person {
+  long id;
+  String name;
+  int age;
+}

src/main/java/com/howtodoinjava/json/JsonArrayToList.java

@@ -1,11 +1,13 @@
-import java.util.concurrent.StructuredTaskScope;
+package com.howtodoinjava.newFeatures.java21;
+
+//import java.util.concurrent.StructuredTaskScope;
 
 public class ScopedValueTest {
 
   //public static ThreadLocal<String> CONTEXT = ThreadLocal.withInitial(() -> null);
   //public static InheritableThreadLocal<String> CONTEXT = new InheritableThreadLocal();
 
-  private static final ScopedValue<String> CONTEXT = ScopedValue.newInstance();
+  //private static final ScopedValue<String> CONTEXT = ScopedValue.newInstance();
 
 
 
@@ -33,15 +35,15 @@ public static void main(String[] args) {
 
     ScopedValueTest instance = new ScopedValueTest();
 
-    ScopedValue.runWhere(CONTEXT, "Test Value", () -> {
+    /*ScopedValue.runWhere(CONTEXT, "Test Value", () -> {
 
       System.out.println("In parent thread start the scoped value is: " + CONTEXT.get());
       instance.doSomething();
       System.out.println("In parent thread end the scoped value is: " + CONTEXT.get());
     });
 
     System.out.println("Outside bounded scope isBound() is: " + CONTEXT.isBound()); 
-    System.out.println("Outside bounded scope the scoped value is: " + CONTEXT.orElse(null));
+    System.out.println("Outside bounded scope the scoped value is: " + CONTEXT.orElse(null));*/
 
 
 
@@ -72,17 +74,17 @@ public static void main(String[] args) {
     parentThread.start();*/
   }
 
-  public void doSomething() {
+  /*public void doSomething() {
     System.out.println("In doSomething() and parent scope: " + CONTEXT.get());
     ScopedValue.runWhere(CONTEXT, "Changed Value", () -> {
       System.out.println("In doSomething() and child scope: " + CONTEXT.get());
       doSomethingAgain();
     });
-  }
+  }*/
 
-  public void doSomethingAgain() {
+  /*public void doSomethingAgain() {
     System.out.println("In doSomethingAgain() and child scope: " + CONTEXT.get());
-  }
+  }*/
 
   /*static void doSomething() {
       System.out.println("Scoped Value in doSomething(): " + CONTEXT.get());

src/main/java/com/howtodoinjava/newFeatures/java21/ScopedValueTest.java

@@ -0,0 +1,5 @@
+[
+  {"id":1,"name":"Alex","age":41},
+  {"id":2,"name":"Brian","age":42},
+  {"id":3,"name":"Charles","age":43}
+]