No serializer found for class org.hibernate.proxy.pojo.javassist.Javassist?

I am working on SpringMVC, Hibernate & JSON but I am getting this error.

HTTP Status 500 - Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) 

Please check my Entity below

    @Entity
@Table(name="USERS")
public class User {

    @Id
    @GeneratedValue
    @Column(name="USER_ID")
    private Integer userId;

    @Column(name="USER_FIRST_NAME")
    private String firstName;

    @Column(name="USER_LAST_NAME")
    private String lastName;


    @Column(name="USER_MIDDLE_NAME")
    private String middleName;

    @Column(name="USER_EMAIL_ID")
    private String emailId;

    @Column(name="USER_PHONE_NO")
    private Integer phoneNo;

    @Column(name="USER_PASSWORD")
    private String password;

    @Column(name="USER_CONF_PASSWORD")
    private String  confPassword;

    @Transient
    private String token;

    @Column(name="USER_CREATED_ON")
    private Date createdOn;

    @OneToMany(fetch=FetchType.EAGER,cascade=CascadeType.ALL)
    @Fetch(value = FetchMode.SUBSELECT)
    @JoinTable(name = "USER_ROLES", joinColumns = { @JoinColumn(name = "USER_ID") }, inverseJoinColumns = { @JoinColumn(name = "ROLE_ID") })
    private List<ActifioRoles> userRole = new ArrayList<ActifioRoles>();


    @OneToMany(fetch=FetchType.EAGER,cascade=CascadeType.ALL,mappedBy="userDetails")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<com.actifio.domain.Address> userAddress = new ArrayList<com.actifio.domain.Address>();

    @OneToOne(cascade=CascadeType.ALL)
    private Tenant tenantDetails;


    public Integer getUserId() {
        return userId;
    }
    public void setUserId(Integer userId) {
        this.userId = userId;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getEmailId() {
        return emailId;
    }
    public void setEmailId(String emailId) {
        this.emailId = emailId;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getConfPassword() {
        return confPassword;
    }
    public void setConfPassword(String confPassword) {
        this.confPassword = confPassword;
    }
    public Date getCreatedOn() {
        return createdOn;
    }
    public void setCreatedOn(Date createdOn) {
        this.createdOn = createdOn;
    }

    public List<ActifioRoles> getUserRole() {
        return userRole;
    }

    public void setUserRole(List<ActifioRoles> userRole) {
        this.userRole = userRole;
    }
    public String getMiddleName() {
        return middleName;
    }
    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }
    public Integer getPhoneNo() {
        return phoneNo;
    }
    public void setPhoneNo(Integer phoneNo) {
        this.phoneNo = phoneNo;
    }

    public List<com.actifio.domain.Address> getUserAddress() {
        return userAddress;
    }
    public void setUserAddress(List<com.actifio.domain.Address> userAddress) {
        this.userAddress = userAddress;
    }
    public Tenant getTenantDetails() {
        return tenantDetails;
    }
    public void setTenantDetails(Tenant tenantDetails) {
        this.tenantDetails = tenantDetails;
    }
    public String getToken() {
        return token;
    }
    public void setToken(String token) {
        this.token = token;
    }

    }

How can I Solve this?

I had a similar problem with lazy loading via the hibernate proxy object. Got around it by annotating the class having lazy loaded private properties with:

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})

I assume you can add the properties on your proxy object that breaks the JSON serialization to that annotation.

The problem is that entities are loaded lazily and serialization happens before they get loaded fully.

Hibernate.initialize(<your getter method>);

Just to add this in, I ran into this same issue, but the supplied answers did not work. I fixed it by taking the exception's suggestion and adding to the application.properties file...

spring.jackson.serialization.fail-on-empty-beans=false

I'm using Spring Boot v1.3 with Hibernate 4.3

It now serializes the entire object and nested objects.

EDIT: 2018

Since this still gets comments I'll clarify here. This absolutely only hides the error. The performance implications are there. At the time, I needed something to deliver and work on it later (which I did via not using spring anymore). So yes, listen to someone else if you really want to solve the issue. If you just want it gone for now go ahead and use this answer. It's a terrible idea, but heck, might work for you. For the record, never had a crash or issue again after this. But it is probably the source of what ended up being a SQL performance nightmare.

As it is correctly suggested in previous answers, lazy loading means that when you fetch your object from the database, the nested objects are not fetched (and may be fetched later when required).

Now Jackson tries to serialize the nested object (== make JSON out of it), but fails as it finds JavassistLazyInitializer instead of normal object. This is the error you see. Now, how to solve it?

As suggested by CP510 previously, one option is to suppress the error by this line of configuration:

spring.jackson.serialization.fail-on-empty-beans=false

But this is dealing with the symptoms, not the cause. To solve it elegantly, you need to decide whether you need this object in JSON or not?

1. Should you need the object in JSON, remove the FetchType.LAZY option from the field that causes it (it might also be a field in some nested object, not only in the root entity you are fetching).

2. If do not need the object in JSON, annotate the getter of this field (or the field itself, if you do not need to accept incoming values either) with @JsonIgnore, for example:

   // this field will not be serialized to/from JSON @JsonIgnore private NestedType secret;

Should you have more complex needs (e.g. different rules for different REST controllers using the same entity), you can use jackson views or filtering or for very simple use case, fetch nested objects separately.

You could use the add-on module for Jackson which handles Hibernate lazy-loading.

More info on https://github.com/FasterXML/jackson-datatype-hibernate wich support hibernate 3 and 4 separately.

I think that the problem is the way that you retrieve the entity.

Maybe you are doing something like this:

Person p = (Person) session.load(Person.class, new Integer(id));

Try using the method get instead of load

Person p = (Person) session.get(Person.class, new Integer(id));

The problem is that with load method you get just a proxy but not the real object. The proxy object doesn't have the properties already loaded so when the serialization happens there are no properties to be serialized. With the get method you actually get the real object, this object could in fact be serialized.