使用GSON将JSON反序列化为Java对象时遇到麻烦

Question

我一直在努力学习GSON，但我很挣扎。我试图反序列化JSON文件到Java对象，使用GSON。我在这里读了无数的问题，但无论如何，我都不明白我到底做错了什么。

这是我的JSON文本:

{
"movies": [
{
"name": "The Shawshank Redemption",
"url": "https://parsehub.com/sandbox/moviedetails?movie=The%20Shawshank%20Redemption",
"IMAX": "06:00 PM",
"rating": "9 . 2",
"cast": [
{
"character": "Andy Dufresne",
"actor": "Tim Robbins"
},
{
"character": "Ellis Boyd 'Red' Redding",
"actor": "Morgan Freeman"
},
{
"character": "Warden Norton",
"actor": "Bob Gunton"
},
{
"character": "Heywood",
"actor": "William Sadler"
}
]
},
{
"name": "Schindler's List",
"url": "https://parsehub.com/sandbox/moviedetails?movie=Schindler%27s%20List",
"IMAX": "06:15 PM",
"rating": "8 . 9",
"cast": [
{
"character": "Oskar Schindler",
"actor": "Liam Neeson"
},
{
"character": "Itzhak Stern",
"actor": "Ben Kingsley"
},
{
"character": "Amon Goeth",
"actor": "Ralph Fiennes"
}
]
}
]
}

下面是我的Java代码:

import com.google.gson.Gson;
import java.io.*;
import java.lang.reflect.Type;
import java.util.ArrayList;
public class Main {
public static void main(String[] args) throws FileNotFoundException {
Gson gson = new Gson();
Movies[] movies = gson.fromJson(new FileReader("src/main/input.json"), (Type) Movies.class);
System.out.println(movies[0]);
}
class Movies {
String name;
String url;
String IMAX;
String rating;
ArrayList<Cast> cast;
}
class Cast {
ArrayList<CastMember> castMembers;
}
class CastMember{
String character;
String actor;
}
}

当我运行这个时，我得到以下错误:

Exception in thread "main" java.lang.ClassCastException: class com.Main$Movies cannot be cast to class [Lcom.Main$Movies; (com.Main$Movies and [Lcom.Main$Movies; are in unnamed module of loader 'app')
at com.Main.main(Main.java:13)

Answer 1

要反序列化的JSON表示一个对象，上面有一个对象列表。您试图反序列化到的Java对象需要与之匹配。

首先，创建新类MovieList。

class MovieList {
List<Movie> movies;
}

更新你的Movies类为Movie，因为它代表一个电影。

class Movie {
String name;
String url;
String IMAX;
String rating;
List<Cast> cast;
}

现在尝试用下面的

调用gson.fromJson(...)

MovieList movieList = gson.fromJson(new FileReader("src/main/input.json"), MovieList.class);
System.out.println(movieList.getMovies().get(0));

Answer 2

尝试使用

Gson gson = new Gson();
Movies[] movies = gson.fromJson(new JsonReader(new FileReader("src/main/input.json"))),Movies[].class);

或者类似

的东西

Type listType = new TypeToken<List<Movies>>() {}.getType();
List<Movies> movies = new Gson().fromJson(new JsonReader(new FileReader("src/main/input.json"))), listType);