JSON 解析错误：无法从 START_OBJECT 令牌中反序列化 java.util.ArrayList 的实例

Posted 2023-02-27

【中文标题】JSON 解析错误：无法从 START_OBJECT 令牌中反序列化 java.util.ArrayList 的实例

【英文标题】：JSON parse error: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

【发布时间】：2018-01-21 15:57:32

【问题描述】：

我在我的项目中使用 spring boot 和 spring 数据，我有两个类：

@Entity
public class Mission implements Serializable 
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY )
    private Long              id;
    private String            departure;
    private String            arrival;
    private Boolean           isFreeWayEnabled;
    @OneToMany( mappedBy = "mission" )
    private List<Station>     stations;
    // getters and setters

第二类：

@Entity
public class Station implements Serializable 
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY )
    private Long              id;
    private String            station;

    @ManyToOne( fetch = FetchType.LAZY )
    @JsonBackReference
    private Mission           mission;
    //getters and setters

和控制器：

@RequestMapping( value = "mission/addMission", method = RequestMethod.POST, consumes = "application/json;charset=UTF-8" )
public Reponse addMission( @RequestBody Mission mission ) throws ServletException 
    if ( messages != null ) 
        return new Reponse( -1, messages );
    
    boolean flag = false;
    try 
        application.addMision( mission );
        application.addStation( mission.getStations(), mission.getId() );
        flag = true;
     catch ( Exception e ) 
        return new Reponse( 5, Static.getErreursForException( e ) );
    
    return new Reponse( 0, flag );

问题是当我尝试使用 JSON 添加新任务时：

"departure":"fff","arrival":"ffff","isFreeWayEnabled":false,stations:"id":1

【问题讨论】：

你能分享你想要反序列化的json吗？

以上："departure":"fff","arrival":"ffff","isFreeWayEnabled":false,"stations":"id":1

【参考方案1】：

您正在尝试将对象反序列化为列表。您需要将 Stations 设为 JSON 数组

"departure":"fff","arrival":"ffff","isFreeWayEnabled":false,stations:["id":1, "id":2]