如何将包含自定义对象列表的映射字段的自定义对象转换为 json？

Question

比方说，我有一个员工 class，看起来像这样：

public class Employee{

Map<String, ArrayList<Salary>> salary = new HashMap<String, ArrayList<Salary>>();
String name;
String age;
}

public class Salary{
String amount;
String currency;
}

Javato/fromJson最聪明的转换方式是什么？

或者；

如果我的 json 看起来像这样怎么办：

  {
  "name": "Test",
  "age": "12",
  "salary": {
    "first": {
      "41130": {
        "amount": "100",
        "currency": "€"
      },
      "41132": {
        "amount": "100",
        "currency": "€"
      }
    },
    "second": {
      "41129": {
        "amount": "100",
        "currency": "€"
      }
    }
  }
}

当我尝试将其转换为 Employee 时出现以下错误。

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT

Answer 1

最聪明的方法，如果您打算在 Web 环境中使用 JSON 是使用 Jackson、JAXB 或您的基础结构已经提供的任何东西，例如让您首选的 REST 基础架构为您完成这项工作。

您需要提供更多关于应用程序用途或所需架构的上下文。

Answer 2

我想你可以使用 Jackson ObjectMapper https://fasterxml.github.io/jackson-databind/javadoc/2.7/com/fasterxml/jackson/databind/ObjectMapper.html#writeValue(java.io.OutputStream,%20java.lang.Object)

ObjectMapper objectMapper = new ObjectMapper();
Employee employee = new Employee();
objectMapper.writeValue(new FileOutputStream("data/output.json"), employee);

Answer 3

public class Main {

    public static void main(String[] args) {

        Gson gson = new Gson();

        Map<String, ArrayList<Salary>> sal = new HashMap<String, ArrayList<Salary>>();
        ArrayList<Salary> salaries = new ArrayList<Salary>();
        Salary salary1 = new Salary("100", "€");
        Salary salary2 = new Salary("200", "€");
        salaries.add(salary1);
        salaries.add(salary2);
        sal.put("1", salaries);
        Employee employee = new Employee(sal, "Test", "12");

        System.out.println("Age -> " + employee.getAge());
        System.out.println("Name -> " + employee.getName());
        System.out.println("Salary -> " + employee.getSalary());

        String json = gson.toJson(employee);
        System.out.println("Json -> " + json);

        Employee employee1 = gson.fromJson(json, Employee.class);

        System.out.println("Age1 -> " + employee1.getAge());
        System.out.println("Name1 -> " + employee1.getName());
        System.out.println("Salary1 -> " + employee1.getSalary());
    }

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public static class Employee{

        Map<String, ArrayList<Salary>> salary = new HashMap<String, ArrayList<Salary>>();
        String name;
        String age;
    }

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public static class Salary{
        String amount;
        String currency;

    }
}

如何将包含自定义对象列表的映射字段的自定义对象转换为 json？

How to convert custom object with map field that includes list of custom object to json?

java

json

jackson

gson