JsonMappingException: Can not instantiate value of type [simple type, a.b.c.Company] from JSON String; no single-String constructor/factory method

Question

I have just added a REST api to my existing Spring + BlazeDS + Hibernate server and everything appears to work when data is retrieved and serialised as JSON but when I try and POST data to be de-serialised into a POJO I get the an exception.

I was under the impression that the spring annotations and the presence of the Jackson jars in the class path would be all that was required, at least it was for my list, get, delete methods that had simple parameters.

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class com.twoh.dto.Company] from JSON String; no single-String constructor/factory method

Here's the method being called:

public abstract class BaseEntityService<T extends BaseEntity> implements IBaseEntityService<T> {

private IBaseEntityDAO<T> DAO;

@Autowired
private ValidationResultHelper validationResultHelper;

public void setDAO(IBaseEntityDAO<T> DAO) {
    this.DAO = DAO;
}

...
@Secured("ROLE_USER")
@RequestMapping(value="/create", method=RequestMethod.POST)
public @ResponseBody ValidationResult create(@RequestBody T entity) {
    ValidationResult result = null;
    try {
        result = DAO.persistEntity(entity);
    } catch(JDBCException e) {
        result = ExceptionHelper.getValidationResult(e);
    } catch(DataIntegrityViolationException e) {
        result = ExceptionHelper.getValidationResult(e);
    }
    validationResultHelper.log(DAO.getSession(), entity.getId(), entity.getClass(), result);
    return result;
}
}

and here is the full exception:

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class com.twoh.dto.Company] from JSON String; no single-String constructor/factory method
at org.codehaus.jackson.map.deser.std.StdValueInstantiator._createFromStringFallbacks(StdValueInstantiator.java:379)
at org.codehaus.jackson.map.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:268)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromString(BeanDeserializer.java:759)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:585)
at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2723)
at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1914)
at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readInternal(MappingJacksonHttpMessageConverter.java:135)
at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:154)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.readWithMessageConverters(HandlerMethodInvoker.java:633)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveRequestBody(HandlerMethodInvoker.java:597)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:346)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:669)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:585)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:311)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:116)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:101)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:182)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:173)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)

Update: added definition of Company DTO

@CheckDictionaryProperty.List({
    @CheckDictionaryProperty(propertyName="partyId", dictionaryName="Party")
})
@Unique.List({
    @Unique(properties = {"code"}, message = "UNIQUE_CODE"),
    @Unique(properties = {"name"}, message = "UNIQUE_NAME")
})
@Entity
@FXClass
@Table(name="edrcompany")
@JsonAutoDetect
public class Company extends BaseEntity {

    private static final long serialVersionUID = 1L;

    public Company(){}

    @NotBlank
    @Column
    private String name;
    public String getName(){ return this.name; }
    public void setName(String name){ this.name = name; }

    @Column
    private String code;
    public String getCode() { return this.code; }
    public void setCode(String code) { this.code = code; }

    @NotNull
    @Column(name="party_id")
    private Integer partyId;
    public Integer getPartyId() { return this.partyId; }
    public void setPartyId(Integer partyId) { this.partyId = ValueHelper.isNullOrZero(partyId) ? null : partyId; }

    @ElementCollection(targetClass=Integer.class, fetch=FetchType.EAGER)
    @Fetch(FetchMode.SUBSELECT)
    @CollectionTable(name="edrcompanyadminlink", joinColumns={@JoinColumn(name="company_id")})
    @Column(name="user_id")
    private Collection<Integer> adminUserIdList = new HashSet<Integer>();
    public Collection<Integer> getAdminUserIdList() { return this.adminUserIdList; }
    public void setAdminUserIdList (Collection<Integer> adminUserIdList) { this.adminUserIdList = adminUserIdList; }    


}


@MappedSuperclass
@FXClass
public abstract class BaseEntity implements Serializable  {

    private static final long serialVersionUID = 1L;

    public BaseEntity(){}

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = ValueHelper.isNullOrZero(id) ? null : id; }

    @Column(name="ENTITY_UID", unique=true, nullable=false, updatable=false, length=36)
    /* Assign a default whenever this class is instantiated Hibernate will 
     * overwrite it when retrieving an entity from the DB.
     */
    private String uid = UUID.randomUUID().toString();
    public String getUID() { return uid; };
    public void setUID(String uid) { this.uid = uid; }

    @Version
    @Column
    private Integer version;
    @FXIgnore
    public Integer getVersion() { return this.version; }
    public void setVersion(Integer version) { this.version = version; }

    // Fake property so that DTO2FX will put it in
    public String getClassName() { return this.getClass().getName(); }
    @JsonIgnore
    public void setClassName(String className) { throw new UnsupportedOperationException(); }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;

        if (o == null || !(o instanceof BaseEntity)) return false;

        BaseEntity other = (BaseEntity) o;

        // if the id is missing, return false
        if (uid == null) return false;

        // equivalence by uid
        return uid.equals(other.getUID());
    }

    @Override
    public int hashCode() {
        if (uid != null) {
            return uid.hashCode();
        } else {
            return super.hashCode();
        }
    }

    @Override
    public String toString() {
        return this.getClassName() + ": " + this.getId();
    }

}

Update If I amend the DTO so that Jackson ignores the Company.adminUserIdList property then the record is created successfully.

@JsonIgnore
public Collection<Integer> getAdminUserIdList() { return this.adminUserIdList; }
@JsonIgnore
public void setAdminUserIdList (Collection<Integer> adminUserIdList) { this.adminUserIdList = adminUserIdList; }

Update Here is the Json as returned by the /company/get/1 method using FireFox RESTClient

{
  "partyId":1,
  "adminUserIdList":[21],
  "name":"2H Mechanical LLC",
  "code":null,
  "uid":"fc5e15e7-a9a7-11e1-be90-7d08b05cbb96",
  "id":1,
  "className":"com.twoh.dto.Company",
  "version":0
}

I was using a similar pattern (less the "id" and a different "uid")for the /compamy/create call with a Content-type=application/json header

Shouldn't 'com.twoh.dto.Company' have a single-string constructor according to the error message? — Stan, May 31 '12 at 19:16
That is what the message implies, but if it serializes to JSON automagically why not the other direction. If I have to write a method that does the work it seems to defeat the object. In a similar question http://stackoverflow.com/questions/8369260/jackson-throws-jsonmappingexception-on-deserialize-demands-single-string-constr that is what was done but none of the examples I have seen of Spring REST services suggest this is necessary for each of the POJOs. — hairyone, May 31 '12 at 20:30
Could you possibly provide declaration of the com.twoh.dto.Company class? — Stan, May 31 '12 at 20:54
I was using Jackson 1.9.2 I rolled back to 1.4.5 which is similar to what was available when Spring 3.0.6 out and I get a different but similar error "Can not deserialize instance of com.twoh.dto.Company out of VALUE_STRING token" — hairyone, May 31 '12 at 22:18
I think you should try to replace the general type definition Collection for AdminUserIdList's getter and setter to the concrete HashSet. — Stan, Jun 01 '12 at 09:28

score 13 · Answer 1 · answered Jun 15 '12 at 10:25

13

I solved the same problem by fixing the JSON I was sending to the server; it was invalid. I removed the "," characters at the end of the last attributes and it worked. I hope it helps

answered Jun 15 '12 at 10:25

Techky

431
4
10

2

Similar issue for me ... I was sending the json as `{"currency":"1"}` to be mapped against a POJO that should have yielded `` in its xml format ... but I faced the error talked about in this thread ... until I fixed my json to be `{"currency":{"id":"1"}}` – pulkitsinghal May 30 '13 at 06:46

DivDiff · Answer 2 · 2019-01-30T20:43:55.827

4

Similar to @Nirmal, I passed in JSON which was contained within double quotes:

"{ "SomeJSON":"Value" }"

instead of

{ "SomeJSON":"Value" }

Removing the "s resolved the issue.

edited Jan 30 '19 at 20:43

answered Jun 12 '18 at 21:37

DivDiff

963
2
10
22

I don't see the difference between the two examples - help? – rich p Jan 30 '19 at 19:22
1

The edit removed what I was trying to illustrate. Have another look. – DivDiff Jan 30 '19 at 20:44

score 0 · Answer 3 · answered Apr 27 '17 at 04:20

0

In my case, I was missing starting and ending curly braces.

answered Apr 27 '17 at 04:20

Nirmal Mangal

812
1
12
26

score 0 · Answer 4 · answered Mar 16 '20 at 22:43

0

Also, I got this error message when I tried to instantiate an enum that wasn't properly defined in my swagger file. See How to define enum in swagger.io?

answered Mar 16 '20 at 22:43

Steve Stilson

1,015
7
11

score 0 · Answer 5 · answered Apr 05 '21 at 15:12

0

In my case, the problem is a space after the key.

{
    "key " : "001" , //There is a space after the key
    "name" : "ABC"
}

Removed the space after the key working fine.

answered Apr 05 '21 at 15:12

Yuvaraj S

301
3
15

Sushank Hegde · Answer 6 · 2022-11-16T11:55:20.027

The possible reason for this issue might be, at the publisher side, you might be converting from object to string more than once, so at consumer end, its not able to read the string into the desired object.

For example : Lets say with kafka/rmq, where you have User object and you have publisher and consumer, so at the publisher end you might have converted the User to string form using object mapper and again you might have converted the string to string using object mapper. So at consumer end while processing this type of string into User object, it will throw this exception

So the fix would be just convert the Object into string only once and then publish, so the consumer can read the string and convert to the desired object(User object in this case) easily.

JsonMappingException: Can not instantiate value of type [simple type, a.b.c.Company] from JSON String; no single-String constructor/factory method

6 Answers6

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