问题描述
在此春季启动项目中,当POST
ing(使用Postman)时,我收到一条错误消息)新的Item
资源
In this spring boot project I get an error when POST
ing (using Postman) a new Item
resource
Resolving exception from handler
[public com.example.demo.resource.Item com.example.demo.controller.ItemController.addItem(com.example.demo.resource.Item)]:
org.springframework.web.HttpMediaTypeNotSupportedException:
Content type 'application/json;charset=UTF-8' not supported
在请求正文中,我复制了从GET
请求中获得的现有Item
之一(并更改了id
和itemName
)
In the request body I copied one of the existing Item
s that I got from a GET
request (and changed the id
and itemName
)
// Request body:
{
"id": 10, // also tried without id field as it's autogenerated
"itemName": "milk",
"cart": {
"id": 1
}
}
我确保在Item
类中具有正确的getter和setter方法(因为这是)
I made sure that I have the correct getters and setters in the Item
class (as this is a known issue)
@Entity
@Table(name="items")
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
@JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Item
{
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "item_id")
private long id;
@Column(name="item_name")
private String itemName;
@ManyToOne
@JoinColumn(name = "cart_id", nullable=false)
@JsonManagedReference
private Cart cart;
//setters and getters
}
这里也是Item
与它具有many-to-one
关系的Cart
类
Here is also the Cart
class to which Item
has a many-to-one
relationship
@Entity
@Table(name="carts")
@JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Cart
{
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "cart_id")
private long id;
@OneToMany(mappedBy = "cart")
@JsonBackReference
private Set<Item> items;
//setters and getters
}
这是ItemController
@RestController
public class ItemController
{
private static final Logger LOG = LoggerFactory.getLogger(ItemController.class);
@Autowired ItemDao dao;
@GetMapping("items")
public List<Item> getAll()
{
List<Item> res = new ArrayList<>();
dao.findAll().forEach(res::add);
return res;
}
@PostMapping("items")
public Item addItem(@RequestBody Item item)
{
return dao.save(item);
}
@GetMapping("items/{item_id}")
public Item getItemById(@PathVariable("item_id") long item_id)
{
Item item = dao.findById(item_id).get();
LOG.info(" ---------------- Retrieved item: {}", item.toString());
return item;
}
}
编辑
我刚刚发现前面似乎还有另一个错误:
I just noticed that there seems to be another error preceding:
Failed to evaluate Jackson deserialization for type [[simple type, class com.example.demo.resource.Item]]: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot handle managed/back reference 'defaultReference': back reference type (java.util.Set) not compatible with managed type (com.example.demo.resource.Item)
这是完整的错误:
2018-02-27 11:03:09.836 WARN 9640 --- [nio-9200-exec-1] .c.j.MappingJackson2HttpMessageConverter : Failed to evaluate Jackson deserialization for type [[simple type, class com.example.demo.resource.Item]]: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot handle managed/back reference 'defaultReference': back reference type (java.util.Set) not compatible with managed type (com.example.demo.resource.Item)
2018-02-27 11:03:09.837 WARN 9640 --- [nio-9200-exec-1] .c.j.MappingJackson2HttpMessageConverter : Failed to evaluate Jackson deserialization for type [[simple type, class com.example.demo.resource.Item]]: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot handle managed/back reference 'defaultReference': back reference type (java.util.Set) not compatible with managed type (com.example.demo.resource.Item)
2018-02-27 11:03:09.838 DEBUG 9640 --- [nio-9200-exec-1] .w.s.m.m.a.ServletInvocableHandlerMethod : Failed to resolve argument 0 of type 'com.example.demo.resource.Item'
org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json;charset=UTF-8' not supported
感谢您的帮助
推荐答案
您不能将Collection, Map, Array or enumeration
用作@JsonBackReference
.
尝试互换@JsonBackReference
和@JsonManagedReference
.应该可以.
Try interchanging @JsonBackReference
and @JsonManagedReference
. It should work.
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