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当前正在尝试使用Gson. File解析下面的复杂Json文件，如下所示-
{“名称”：“ABC”，“D1”：“ABC”，“描述”：“ABC”，“标签”：[“A：1”、“B：2”]、“系统1”：{“密钥1”：“AA”，“验证1”：“瓦尔”、“配置文件”：空，“路径”：空，“名称”：空，“位置”：“美国”、“是真的”：假，“路径”：“/ABC”，“国家/地区”：[“A1”、“A2”、“A3”] }，“格式”：{“X”：100，“Y”：100，“位置X”：0，“位置Y”：0 }，“类型”：“A1”}
为解析Json而创建的类

package Model;

import java.util.ArrayList;

public class Gson_toJava {
 private String Name;
 private String D1;
 private String Description;
 ArrayList < Object > Tags = new ArrayList < Object > ();
 System1 System1Object;
 Format1 Format1Object;
 private String Type;

 // Getter Methods 

 public String getName() {
  return Name;
 }

 public String getD1() {
  return D1;
 }

 public String getDescription() {
  return Description;
 }

 public System1 getSystem1() {
  return System1Object;
 }

 public Format1 getFormat1() {
  return Format1Object;
 }

 public String getType() {
  return Type;
 }

 // Setter Methods 

 public void setName(String Name) {
  this.Name = Name;
 }

 public void setD1(String D1) {
  this.D1 = D1;
 }

 public void setDescription(String Description) {
  this.Description = Description;
 }

 public void setSystem1(System1 System1Object) {
  this.System1Object = System1Object;
 }

 public void setFormat1(Format1 Format1Object) {
  this.Format1Object = Format1Object;
 }

 public void setType(String Type) {
  this.Type = Type;
 }
}

package Model;

import java.util.ArrayList;

public class System1 {
 private String Key1;
 private String Val1;
 private String Profile = null;
 private String Path = null;
 private String Name = null;
 private String Location;
 private boolean IsTrue;
 private String Path1;
 ArrayList < Object > Countries = new ArrayList < Object > ();

 // Getter Methods 

 public String getKey1() {
  return Key1;
 }

 public String getVal1() {
  return Val1;
 }

 public String getProfile() {
  return Profile;
 }

 public String getPath() {
  return Path;
 }

 public String getName() {
  return Name;
 }

 public String getLocation() {
  return Location;
 }

 public boolean getIsTrue() {
  return IsTrue;
 }

 public String getPath1() {
  return Path1;
 }

 // Setter Methods 

 public void setKey1(String Key1) {
  this.Key1 = Key1;
 }

 public void setVal1(String Val1) {
  this.Val1 = Val1;
 }

 public void setProfile(String Profile) {
  this.Profile = Profile;
 }

 public void setPath(String Path) {
  this.Path = Path;
 }

 public void setName(String Name) {
  this.Name = Name;
 }

 public void setLocation(String Location) {
  this.Location = Location;
 }

 public void setIsTrue(boolean IsTrue) {
  this.IsTrue = IsTrue;
 }

 public void setPath1(String Path1) {
  this.Path1 = Path1;
 }
}

package Model;

public class Format1 {
 private float X;
 private float Y;
 private float PositionX;
 private float PositionY;

 // Getter Methods 

 public float getX() {
  return X;
 }

 public float getY() {
  return Y;
 }

 public float getPositionX() {
  return PositionX;
 }

 public float getPositionY() {
  return PositionY;
 }

 // Setter Methods 

 public void setX(float X) {
  this.X = X;
 }

 public void setY(float Y) {
  this.Y = Y;
 }

 public void setPositionX(float PositionX) {
  this.PositionX = PositionX;
 }

 public void setPositionY(float PositionY) {
  this.PositionY = PositionY;
 }
}

现在尝试使用以下代码解析Json-

String content = "";
        try {
            content = new String(Files.readAllBytes(Paths.get("label.json")));
        } catch (IOException e) {
            e.printStackTrace();
        }
        Gson_toJava data = new Gson().fromJson(content, Gson_toJava.class);
    System.out.println(data.getDescription());//Returning ABC
    System.out.println(data.getSystem1());// Returning null
    System.out.println(data.getFormat1());// Returning null

我已经更新了类定义，但是仍然不能得到嵌套的字段。下面显示的是堆栈跟踪

ABC
null
Printing stack trace...
java.lang.NullPointerException
    at com.Gson_Example.GsonEampleApplication.main(GsonEampleApplication.java:31)