Using Jackson2 with Spring 4.0 (MVC + REST+ Hibernate)

Question

I am making a restful application and trying to convert a list of objects into json for a specific url (@RequestMapping / @ResponseBody )

I have jackson-hibernate4 and jackson-core ,databind etc in my classpath.

Here is my object that i want to convert in json.

@Entity
@Table(name="Product")
public class Product {
@Id
@Column(name="productId")
@GeneratedValue
protected int productId;
@Column(name="Product_Name")
protected String name;

@Column(name="price")
protected BigDecimal baseprice;


@OneToMany(cascade = javax.persistence.CascadeType.ALL,mappedBy="product",fetch=FetchType.EAGER)
protected List<ProductOption> productoption = new ArrayList<ProductOption>();

@OneToMany(cascade = javax.persistence.CascadeType.ALL,mappedBy="product",fetch=FetchType.EAGER)
protected List<ProductSubOption> productSubOption = new ArrayList<ProductSubOption>();


@ManyToOne
@JoinColumn(name="ofVendor")
protected Vendor vendor;

The two objects inside Product are also POJO'S..

Here is my method that retrieves the list of product

@Override
public List<Product> getMenuForVendor(int vendorId) {
    List<Product> result = em.createQuery("from "+Product.class.getName()+" where ofVendor = :vendorId").setParameter("vendorId", vendorId).getResultList();
    System.out.println(result.size());
    return result;
}

When i try to return this list in my controller I was getting a "Cannot lazily load for json" so i set my objects to be fetched eagerly. Here is my controller

@Autowired
private MenuDaoImpl ms;

@RequestMapping(value = "/{vendorId}", method = RequestMethod.GET)
public @ResponseBody List<Product> getMenu(@PathVariable int vendorId){

    List<Product> Menu = Collections.unmodifiableList(ms.getMenuForVendor(vendorId));
    return Menu;
}

Now when i hit my url localhost:8080/getMenu/1 I should be getting a json string displayed but I get a big list of errors

WARN : org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver -       Handling of [org.springframework.http.converter.HttpMessageNotWritableException] resulted in Exception
  java.lang.IllegalStateException: Cannot call sendError() after the response has been     committed
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:467)
 Could not write JSON: Infinite recursion (StackOverflowError) (through reference chain:

I am not sure if I am missing anything. Please guide .

Answer 1

I solved it using @JsonBackReference for @ManyToOne binding and @JsonManagedReference on @OneToMany binding.

Thanks "Sotirios Delimanolis"

Answer 2

The question has already been answered. I am simply putting the link of a good example that clearly explains both the problem and the solution. http://geekabyte.blogspot.in/2013/09/fixing-converterhttpmessagenotwritablee.html