我有一个具有这种结构的用户对象:
class User {
private String id;
private String name;
private Map<String, Object> properties;
// GETTERS & SETTERS
}
我有一个具有这种结构的 JSON 字符串:
{
"user": {
"id:"123456789",
"name:"azerty",
"emailHash":"123456789", // not used in User class
"properties": {
"p1":1,
"p2":"test",
"p3":[1, 2, 3, 4],
"p4":{
etc...
}
}
}
}
属性的键是字符串,属性的值可以是字符串、整数、数组、 boolean 值、映射等。
我尝试像这样用 Gson 反序列化这个 JSON 字符串:
JsonParser parser = new JsonParser();
JsonElement element = parser.parse(jsonString);
JsonObject object = element.getAsJsonObject();
GsonBuilder builder = new GsonBuilder();
builder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
Gson gson = builder.create();
User user = (User) gson.fromJson(object.get("user"), new TypeToken<User>() {}.getType());
字段“id”和“name”已正确注入(inject),但字段“properties”保持为空。
你知道我做错了什么吗? 预先感谢您的帮助!
最佳答案
对我来说,这段代码:
public class Main {
public static void main(String[] args) throws IOException {
GsonBuilder builder = new GsonBuilder();
builder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
Gson gson = builder.create();
FileInputStream inputStream = new FileInputStream(new File("bobi.json"));
InputStreamReader reader = new InputStreamReader(inputStream);
User user = gson.fromJson(reader, User.class);
System.out.println(user.getName());
System.out.println(user.getId());
for (String property : user.getProperties().keySet()) {
System.out.println("Key: " + property + " value: " + user.getProperties().get(property));
}
reader.close();
}
打印这个:
azerty
123456789
Key: p1 value: 1.0
Key: p2 value: test
Key: p3 value: [1.0, 2.0, 3.0, 4.0]
Key: p4 value: {}
但是,请记住,我已经在我解析的文件中剥离了包装 json 对象。文件是:
{
"id":"123456789",
"name" : "azerty",
"emailHash":"123456789",
"properties": {
"p1":1,
"p2":"test",
"p3":[1, 2, 3, 4],
"p4":{
}
}
}
我还为 name
和 id
添加了结束双引号,您的示例中没有。
OP 请求的 User
类。出于打印的原因,我添加了 getter 和 setter:
import java.util.Map;
class User {
private String id;
private String name;
private Map<String, Object> properties;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Map<String, Object> getProperties() {
return properties;
}
public void setProperties(Map<String, Object> properties) {
this.properties = properties;
}
}
关于java - 使用 Gson 反序列化 Map<String, Object> 字段,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/14263114/