JsonMappingException when calling a RESTful service

Question

I am using Java8 with Spring, Hibernate and JPA.

I have a RESTful service that saves a Person object:

@RequestMapping(value = "/save", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.APPLICATION_JSON_VALUE)
public @ResponseBody ResponseEntity<Person> savePerson(@RequestBody Person person) {
    try {
        person = personService.save(person);
        return new ResponseEntity<Person>(person, HttpStatus.OK);
    } catch (Exception e) {
        Person p = null;
        return new ResponseEntity<Person>(p, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

I get the following error when trying to merge a Person object:

16:02:58,472 WARN [org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver] (default task-11) Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: N/A at [Source: java.io.PushbackInputStream@7583d44c; line: 29, column: 3] (through reference chain: com.jobs.spring.domain.Person["blockedPersons"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: N/A at [Source: java.io.PushbackInputStream@7583d44c; line: 29, column: 3] (through reference chain: com.jobs.spring.domain.Person["blockedPersons"])

I guess because it talks about a "reference chain", I may have some recursion error. Or for some reason it is struggling to parse the Java into the JSON object.

If anyone can advise, I would appreciate the help.

More info:

Person.java

@Entity
@Table(name = "person")
@XmlRootElement(name = "person")
public class Person extends AbstractDomain<Long> {

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

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
    @JoinTable(name = "person_blocked", joinColumns = {
            @JoinColumn(name = "PER_ID", referencedColumnName = "ID") }, inverseJoinColumns = {
                    @JoinColumn(name = "BLOCK_ID", referencedColumnName = "ID", unique = true) })
    private Set<BlockedPerson> blockedPersons = null;

    ...
}

BlockedPerson.java

@Entity
@Table(name = "blocked_person")
@XmlRootElement(name = "blocked_person")
public class BlockedPerson extends AbstractDomain<Integer> {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "ID", unique = true, nullable = false)
    private Integer id;

    @Column(name = "BLOCKED_PER_ID", nullable = false)
    private Long blockedPersonId;

    @XmlElement
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public Long getBlockedPersonId() {
        return blockedPersonId;
    }

    public void setBlockedPersonId(Long blockedPersonId) {
        this.blockedPersonId = blockedPersonId;
    }

}

Hi CrazySabbath, thanks for the reply. I do have the Person class above showing the @OneToMany field in question. Would you also like me to show the getter and setters? (I only started getting this error when this @OneToMany field was added). — Richard
– Richard, Commented Jul 11, 2017 at 14:20
My bad, missed bolded text lol. Are you passsing entities directly to your controller? I would avoid that. Can you show Person class declaration? And @RequestBody print? If I were you, I would create other classes, with same fields and extending seriazable. Then I would convert those classes to JPA classes. — CrazySabbath
– CrazySabbath, Commented Jul 11, 2017 at 14:25
What's more, if you are using spring, you can add RestController annotations to your controller classes and remove @ResponseBody. — CrazySabbath
– CrazySabbath, Commented Jul 11, 2017 at 14:27
I have updated the code above to show the Person class definition. What do you mean by "And @RequestBody print? "? Also, in the Controller, I tried replacing @ResponseBody with @RestController, but I get: The annotation @RestController is disallowed for this location — Richard
– Richard, Commented Jul 11, 2017 at 14:30

Richard · Accepted Answer · 2017-07-11 15:01:24Z

1

Solution

The reson for the error above is because I was getting an exception in the setter method on Person which was doing the following on a null object.

this.blockedPersons.clear();

Fix:

change:

private Set<BlockedPerson> blockedPersons = null;

to:

private Set<BlockedPerson> blockedPersons = new HashSet<BlockedPerson>();

answered Jul 11, 2017 at 15:01

Richard

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