java - AngularJS 应用程序无法从服务器获取列表(Java Spring)

Question

我尝试加载List<Pick>到我的前端申请表服务器。在服务器上，我有 Spring 应用程序，我使用 hibernate 从数据库加载选择对象

Spring Controller :

@RequestMapping(value = "/web2/getActivePicks", method =  RequestMethod.POST)
public @ResponseBody List<Pick>  getActivePicks() {
    PickDAO pd = new PickDAO();
    List<Pick> picks = pd.getPicksFrom(new Date()); 
    return picks;   
}

当我尝试获取此选择列表时，我得到`

HTTP Status 500 - Could not write JSON: 
(was java.lang.NullPointerException) 
(through reference chain: java.util.ArrayList[0]->com.gepick.app.objects.rmo.Pick["match"]->com.gepick.app.objects.rmo.soccer.Match_soccer["ar"]); 
nested exception is org.codehaus.jackson.map.JsonMappingException: (was java.lang.NullPointerException) 
(through reference chain: java.util.ArrayList[0]->com.gepick.app.objects.rmo.Pick["match"]->com.gepick.app.objects.rmo.soccer.Match_soccer["ar"])

我选择的类别:

@Entity
public class Pick {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int pid;

@OneToOne
private Match_soccer match;

@OneToOne
private Algo1 algo;

@Column(length = 100)
private String pick;

@Column(length = 5)
private double plimit;
....

我将 Controller 更改为:

@RequestMapping(value = "/web2/getActivePicks", method =     RequestMethod.POST)
public @ResponseBody JSONArray  getActivePicks() {
    PickDAO pd = new PickDAO();
    JSONArray picks = new JSONArray(pd.getPicksFrom(new Date()));
    return picks;   
}

但是现在我得到了 http 状态 406 和 messagesgae:

The resource identified by this request is only capable of generating responses 
with characteristics not acceptable according to the request "accept" headers

Answer 1

似乎当 Jackson 时，您的 JSON mapper 试图转换 Pick 实例，Match_soccer 为 null 并引发异常。

您可以看到您的 Match_soccer 在映射之前初始化，或者您可以注释您的 Pick 类有了这个@JsonInclude(Ininclude.NON_NULL)。

This将指示映射器忽略映射中的所有null字段