I am building an application using JPA, JSF, EJB, Derby. At this point the application is still small. I have a form in the application to add new products. When adding data to the db it goes smoothly until I restart the application or the server. When I restart either the server or app I get java.lang.StackOverflowError, I still can query the db for the data represented by the product db, but creation product is not possible. I have only 5 entries in the db, as of now, but I am concerned about this happening so early.
This is the Ejb (Getter, setter and constructors removed for simplicity):
@Stateless
public class ProductEJB{
@PersistenceContext(unitName = "luavipuPU")
private EntityManager em;
public List<Product> findAllProducts()
{
TypedQuery<Product> query = em.createNamedQuery("findAllProducts", Product.class);
return query.getResultList();
}
public Product findProductById(int productId)
{
return em.find(Product.class, productId);
}
public Product createProduct(Product product)
{
product.setDateAdded(productCreationDate());
em.persist(product);
return product;
}
public void updateProduct(Product product)
{
em.merge(product);
}
public void deleteProduct(Product product)
{
product = em.find(Product.class, product.getProduct_id());
em.remove(em.merge(product));
}
this is the ProductController (Getter, setter and constructors removed for simplicity):
@Named
@RequestScoped
public class ProductController {
@EJB
private ProductEJB productEjb;
@EJB
private CategoryEJB categoryEjb;
private Product product = new Product();
private List<Product> productList = new ArrayList<Product>();
private Category category;
private List<Category> categoryList = new ArrayList<Category>();
public String doCreateProduct()
{
product = productEjb.createProduct(product);
productList = productEjb.findAllProducts();
return "listProduct?faces-redirect=true";
}
public String doDeleteProduct()
{
productEjb.deleteProduct(product);
return "deleteProduct?faces-redirect=true";
}
public String cancelDeleteAction()
{
return "listProduct?faces-redirect=true";
}
@PostConstruct
public void init()
{
categoryList = categoryEjb.findAllCategory();
productList = productEjb.findAllProducts();
}
Category Entity (Getters, setters, hash() and constructors removed for simplicity):
@Entity
@NamedQueries({
@NamedQuery(name= "findAllCategory", query="SELECT c FROM Category c")
})
public class Category implements Serializable
{
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy= GenerationType.AUTO)
private int category_id;
private String name;
private String description;
@OneToMany(mappedBy = "category_fk")
private List<Product> product_fk;
// readObject() and writeObject()
private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException
{
// default deserializer
ois.defaultReadObject();
// read the attributes
category_id = ois.readInt();
name = (String)ois.readObject();
description = (String)ois.readObject();
}
private void writeObject(ObjectOutputStream oos) throws IOException, ClassNotFoundException
{
// default serializer
oos.defaultWriteObject();
// write the attributes
oos.writeInt(category_id);
oos.writeObject(name);
oos.writeObject(description);
}
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Category other = (Category) obj;
if (this.category_id != other.category_id) {
return false;
}
if ((this.name == null) ? (other.name != null) : !this.name.equals(other.name)) {
return false;
}
if ((this.description == null) ? (other.description != null) : !this.description.equals(other.description)) {
return false;
}
if (this.product_fk != other.product_fk && (this.product_fk == null || !this.product_fk.equals(other.product_fk))) {
return false;
}
return true;
}
Product Entity (Getters, setters, hash() and constructors removed for simplicity):
@Entity
@NamedQueries({
@NamedQuery(name="findAllProducts", query = "SELECT p from Product p")
})
public class Product implements Serializable
{
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy= GenerationType.AUTO)
private int product_id;
private String name;
private String description;
protected byte[] imageFile;
private Float price;
@Temporal(TemporalType.TIMESTAMP)
private Date dateAdded;
@ManyToOne
private Category category_fk;
@ManyToOne
private SaleDetails saleDetails_fk;
// readObject() and writeObject() methods
private void readObject (ObjectInputStream ois)throws IOException, ClassNotFoundException
{
// default deserialization
ois.defaultReadObject();
// read the attributes
product_id = ois.readInt();
name = (String)ois.readObject();
description = (String)ois.readObject();
for(int i=0; i<imageFile.length; i++ )
{
imageFile[i]=ois.readByte();
}
price = ois.readFloat();
dateAdded = (Date)ois.readObject();
category_fk = (Category)ois.readObject();
saleDetails_fk = (SaleDetails)ois.readObject();
}
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Product other = (Product) obj;
if (this.product_id != other.product_id) {
return false;
}
if ((this.name == null) ? (other.name != null) : !this.name.equals(other.name)) {
return false;
}
if ((this.description == null) ? (other.description != null) : !this.description.equals(other.description)) {
return false;
}
if (!Arrays.equals(this.imageFile, other.imageFile)) {
return false;
}
if (this.price != other.price && (this.price == null || !this.price.equals(other.price))) {
return false;
}
if (this.dateAdded != other.dateAdded && (this.dateAdded == null || !this.dateAdded.equals(other.dateAdded))) {
return false;
}
if (this.category_fk != other.category_fk && (this.category_fk == null || !this.category_fk.equals(other.category_fk))) {
return false;
}
if (this.saleDetails_fk != other.saleDetails_fk && (this.saleDetails_fk == null || !this.saleDetails_fk.equals(other.saleDetails_fk))) {
return false;
}
return true;
}
private void writeObject(ObjectOutputStream oos) throws IOException, ClassNotFoundException
{
// default serialization
oos.defaultWriteObject();
// write object attributes
oos.writeInt(product_id);
oos.writeObject(name);
oos.writeObject(description);
oos.write(imageFile);
oos.writeFloat(price);
oos.writeObject(dateAdded);
oos.writeObject(category_fk);
oos.writeObject(saleDetails_fk);
}
This is the stacktrace:
javax.faces.el.EvaluationException: java.lang.StackOverflowError
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.StackOverflowError
at java.util.Vector$Itr.<init>(Vector.java:1120)
at java.util.Vector.iterator(Vector.java:1114)
at java.util.AbstractList.hashCode(AbstractList.java:540)
at java.util.Vector.hashCode(Vector.java:988)
at org.eclipse.persistence.indirection.IndirectList.hashCode(IndirectList.java:460)
at com.lv.Entity.Category.hashCode(Category.java:96)
at com.lv.Entity.Product.hashCode(Product.java:148)
at java.util.AbstractList.hashCode(AbstractList.java:541)
Your Category class has list of Products and in the equals method of the Category class you are doing
if (this.product_fk != other.product_fk && (this.product_fk == null || !this.product_fk.equals(other.product_fk))) {
return false;
}
which invokes the equals method on the Product class, the equals method on the Product class which does
if (this.category_fk != other.category_fk && (this.category_fk == null || !this.category_fk.equals(other.category_fk))) {
return false;
}
which invokes the equals method on the Category once again and the whole process repeats causing an Stack overflow.
Solution:
Hope it helps.