Question

我正在尝试读取我的 .json 文件。是VehicleRepository类。

"{\"vehicles\":[{\"id\":\"9467d079-4502-4dba-9d23-b8506dfc7ef4\",\"plate\":\"ghghghhg\",\"manufacturer\":\"Alfa Romeo\",\"model\":\"hgghgh\",\"color\":\"Amarelo\"}]}"

这是错误：

com.fasterxml.jackson.databind.exc.MismatchedInputException：无法构造VehicleRepository的实例（尽管存在至少一个创建者）：无法构造VehicleRepository的实例（尽管至少存在一个创建者）：没有[[Source：（File）;行：1，列：1]

我要使用以下方法来创建.json文件：

repository.vehicles = new ArrayList<Vehicle>();
repository.vehicles.add(vehicle);           

json = mapper.writeValueAsString(repository);   

ObjectMapper write = new ObjectMapper();
write.writeValue(new File("Database//Vehicles.json"), json);

要读取.json文件，我正在使用此文件：

VehicleRepository newRepository = mapper.readValue(new File("Database\\Vehicles.json"), VehicleRepository.class);

并且在上面的行中发生了错误。

这是我的Vehicle班：

public class Vehicle {

    private String id;
    private String plate;
    private String manufacturer;
    private String model;
    private String color;

    public Vehicle() {}

    public Vehicle(String plate, String manufacturer, String model, String color) {
        this.id = UUID.randomUUID().toString();
        this.plate = plate;
        this.manufacturer = manufacturer;
        this.model = model;
        this.color = color;
    }

    public Vehicle(String id, String plate, String manufacturer, String model, String color) {
        this.id = id;
        this.plate = plate;
        this.manufacturer = manufacturer;
        this.model = model;
        this.color = color;
    }

    public String getId() {
        return id;
    }

    public String getPlate() {
        return plate;
    }

    public void setPlate(String plate) {
        this.plate = plate;
    }

    public String getManufacturer() {
        return manufacturer;
    }

    public void setManufacturer(String manufacturer) {
        this.manufacturer = manufacturer;
    }

    public String getModel() {
        return model;
    }

    public void setModel(String model) {
        this.model = model;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }
}

这是我的VehicleRepository班：

public class VehicleRepository {

    List<Vehicle> vehicles;

    public VehicleRepository() {

    }

    public List<Vehicle> getVehicles() {
        return vehicles;
    }

    public void setVehicles(List<Vehicle> vehicles) {
        this.vehicles = vehicles;
    }
}

有人可以帮我吗？

Answer 1

代码中的问题是，您首先要将对象转换为String并将该String作为JSON写入文件。

您可以使用以下方法将对象写入文件中：

write.writeValue(new File("Vehicles.json"), repository);

结果将是正确的json：

{"vehicles":[{"id":"9467d079-4502-4dba-9d23-b8506dfc7ef4","plate":"ghghghhg","manufacturer":"Alfa Romeo","model":"hgghgh","color":"Amarelo"}]}

这可以通过您已经拥有的代码完美地阅读：

VehicleRepository newRepository = mapper.readValue(new File("Vehicles.json"), VehicleRepository.class);

MismatchedInputException-杰克逊反序列化

1 个答案: