我有两个实体序列化并使用spring framework 4.2.5 + jacksonjson 2.7.5发送给客户端。我的实体如下：
@Entity
@Table(name = "entrada")
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="idEntrada")
public class EntradaTest implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name = "id_entrada", unique = true, nullable = false)
private String idEntrada;
@Column(nullable = false, length = 5)
private String codigo;
private Integer recibidos;
@ManyToOne
@JsonIdentityReference(alwaysAsId = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "idEmpleado", scope = Empleado.class)
@JoinColumn(name = "id_pesador_bruto")
private Empleado pesadorBruto;
@ManyToOne
@JsonIdentityReference(alwaysAsId = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "dEmpleado", scope = Empleado.class)
@JoinColumn(name = "id_pesador_tara")
private Empleado pesadorTara;
@ManyToOne
@JsonIdentityReference(alwaysAsId = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "idEmpleado", scope = Empleado.class)
@JoinColumn(name = "id_representante_bruto")
private Empleado representanteBruto;
@ManyToOne
@JsonIdentityReference(alwaysAsId = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "idEmpleado", scope = Empleado.class)
@JoinColumn(name = "id_representante_tara")
private Empleado representanteTara;
@ManyToOne
@JoinColumn(name = "id_oficina", nullable = false)
private Entidad oficina;
}
@Entity
@Table(name = "empleado")
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="idEmpleado", scope = Empleado.class)
class Empleadoest implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name = "id_empleado", unique = true, nullable = false)
private String idEmpleado;
@Column(nullable = false, length = 125)
private String nombre;
@OneToMany(mappedBy = "pesadorBruto")
private Set<Entrada> entradasPesadorBruto;
@OneToMany(mappedBy = "pesadorTara")
private Set<Entrada> entradasPesadorTara;
@OneToMany(mappedBy = "representanteBruto")
private Set<Entrada> entradasRepresentanteBruto;
@OneToMany(mappedBy = "representanteTara")
private Set<Entrada> entradasRepresentanteTara;
}
我的REST服务端点是
@RequestMapping(value = "/entradas/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Entrada> getEntrada(@PathVariable("id") String idEntrada) {
Entrada entrada = entradaService.get(idEntrada);
if (entrada == null) {
return new ResponseEntity<Entrada>(HttpStatus.NOT_FOUND);
}
return new ResponseEntity<Entrada>(entrada, HttpStatus.OK);
}
@RequestMapping(value = "/entradas/", method = RequestMethod.POST)
public ResponseEntity<Void> createEntrada(@RequestBody Entrada entrada, UriComponentsBuilder ucBuilder) {
entradaService.save(entrada);
HttpHeaders headers = new HttpHeaders();
headers.setLocation(ucBuilder.path("/entradas/{id}").buildAndExpand(entrada.getIdEntrada()).toUri());
return new ResponseEntity<Void>(headers, HttpStatus.CREATED);
}
我发送给客户端的序列化数据如下：
{
"idEntrada": "e375ecf9-dabd-4c76-8813-0679818f9590",
"codigo": "378-2",
"recibidos": 0,
"pesadorBruto": "0c23c490-a54a-495d-9447-dc6227520646",
"pesadorTara": "874dfe26-11cb-48e4-916e-bf8a83187dcb",
"representanteBruto": "5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"representanteTara": "5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"oficina": {
"idEntidad": "f3964add-3ae8-4392-bafc-cffb9643ec15",
"nombre": "O.P.C.",
},
}
但是当我尝试将数据发送回服务器时，如下所示创建新实体
{
"idEntrada":"e375ecf9-dabd-4c76-8813-0679818f9590",
"codigo":"378-2",
"pesadorBruto":{
"idEmpleado":"0c23c490-a54a-495d-9447-dc6227520646",
"nombre":"J. CABRERA",
},
"pesadorTara":{
"idEmpleado":"874dfe26-11cb-48e4-916e-bf8a83187dcb",
"nombre":"L. A. DELGADO",
},
"representanteBruto":{
"idEmpleado":"5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"nombre":"C. MARQUEZ",
},
"representanteTara":{
"idEmpleado":"5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"nombre":"C. MARQUEZ",
},
"oficina":{
"idEntidad":"f3964add-3ae8-4392-bafc-cffb9643ec15",
"nombre":"O.P.C.",
},
}
杰克逊失败了：
Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException:
Could not read document: Already had POJO for id (java.lang.String)
[[ObjectId: key=5fb567af-805a-40dc-84bc-8f6038d8cd2f,
type=com.fasterxml.jackson.databind.deser.impl.PropertyBasedObjectIdGenerator,
scope=lt.ciader.model.Empleado]]
(through reference chain: lt.ciader.model.Entrada["representanteTara"]->lt.ciader.model.Empleado["idEmpleado"]);
nested exception is com.fasterxml.jackson.databind.JsonMappingException:
Already had POJO for id (java.lang.String)
[[ObjectId: key=5fb567af-805a-40dc-84bc-8f6038d8cd2f,
type=com.fasterxml.jackson.databind.deser.impl.PropertyBasedObjectIdGenerator,
scope=lt.ciader.model.Empleado]]
(through reference chain: lt.ciader.model.Entrada["representanteTara"]->lt.ciader.model.Empleado["idEmpleado"])
我知道代表塔拉是同一个代表布鲁托，但它可以是我的模型相同的就业，甚至pesadorTara和PesadorBruto也是如此。
当我使用不同的empleados发送数据时，我的服务获取数据并将其序列化而没有问题。 我用谷歌搜索找到了解决方案，但我找不到能帮助我的答案。我回顾：
JsonMappingException: Already had POJO for id
Jackson Already had POJO for id
https://groups.google.com/forum/#!topic/jackson-user/TSloBi1C_qk
https://github.com/edwinquaihoi/jsonidentitymanytomany/issues/1
https://github.com/FasterXML/jackson-databind/issues/266
我做错了什么。我该如何解决这个问题。
答案 0 :(得分：1)
经过多次测试，我找到了解决方案。问题是杰克逊失败了因为同一个实体出现了两次。解决方案只发送secon实例中的普通ID，而不是包装在object：
中{
"idEntrada":"e375ecf9-dabd-4c76-8813-0679818f9590",
"codigo":"378-2",
"pesadorBruto":{
"idEmpleado":"0c23c490-a54a-495d-9447-dc6227520646",
"nombre":"J. CABRERA",
},
"pesadorTara":{
"idEmpleado":"874dfe26-11cb-48e4-916e-bf8a83187dcb",
"nombre":"L. A. DELGADO",
},
"representanteBruto":{
"idEmpleado":"5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"nombre":"C. MARQUEZ",
},
"representanteTara": "5fb567af-805a-40dc-84bc-8f6038d8cd2f",
"oficina":{
"idEntidad":"f3964add-3ae8-4392-bafc-cffb9643ec15",
"nombre":"O.P.C.",
},
}