Unable to persist Entity having @OneToMany mapping on a reference in JPA

[R. Jain]

Hello,

I have two entities, ComponentMetaData and ComponentType.

ComponentMetaData.class

@Entity
@Table(name = "component_meta_data")
public class ComponentMetaData implements IComponentMetaData {

	@Id
	@Column(name = "idcomponent_meta_data")
	private int componentId;
	
	@Column(name = "component_name")
	private String componentName;
	
	@Column(name = "component_desc")
	private String componentDesc;
	
	@JoinColumn(name = "component_type_id", referencedColumnName = "idcomponent_type")
	@ManyToOne(cascade = CascadeType.ALL, targetEntity = ComponentType.class)
	private ComponentType componentType;
	
	@JoinColumn(name = "user_email", referencedColumnName = "email")
	@ManyToOne(cascade = CascadeType.ALL, targetEntity = User.class)
	private User user;
	
	
	public ComponentMetaData() {
		
	}
	
	public ComponentMetaData(String componentName, String componentDesc, 
					ComponentType componentType, User user) {
		
		setComponentName(componentName);
		setComponentDesc(componentDesc);
		setComponentType(componentType);
		setUser(user);
	}
	
	@Override
	public int getComponentId() {
		return this.componentId;
	}

	@Override
	public String getComponentName() {
		return this.componentName;
	}

	@Override
	public String getComponentDesc() {
		return this.componentDesc;
	}

	@Override
	public ComponentType getComponentType() {
		return this.componentType;
	}

	@Override
	public User getUser() {
		return this.user;
	}

	@Override
	public void setComponentName(String componentName) {
		this.componentName = componentName;
	}

	@Override
	public void setComponentDesc(String componentDesc) {
		this.componentDesc = componentDesc;
	}

	public void setComponentType(ComponentType componentType) {
		this.componentType = componentType;
	}

	public void setUser(User user) {
		this.user = user;
	}
}

ComponentType.class

@Entity
@Table(name = "component_type")
public class ComponentType implements IComponentType {

	@Id
	@Column(name = "idcomponent_type")
	private int typeId;
	
	@Column(name = "type_name")
	private String typeName;
	
	
	public ComponentType() {
	}
	
	public ComponentType(String typeName) {
		this.setTypeName(typeName);
	}
	
	@Override
	public void setTypeId(int typeId) {
		this.typeId = typeId;
	}
	
	@Override
	public int getTypeId() {
		return this.typeId;
	}

	@Override
	public String getTypeName() {
		return this.typeName;
	}

	@Override
	public void setTypeName(String typeName) {
		this.typeName = typeName;
	}

}

Now when I am trying to persist the ComponentMetaData Object. It is throwing Transaction RollBack Exception.
Because it also tries to run an insert query in ComponentType table (Which of course it will not be able to do) .. As it will generate duplicate primary key entry...

This is how I am persisting...

        @Override
	public ComponentMetaData createComponent(String componentName,
			String componentDesc, String componentTypeName, String email) {
		
		
		ComponentType componentType = this.getComponentTypeByName(componentTypeName);
		User user = this.getUserByEmail(email);
		System.out.println("ComponentTypeId : " + componentType.getTypeId());            /* Prints 2 */
		init();
		transaction.begin();
		
		ComponentMetaData compMetaData = new ComponentMetaData(componentName, 
												componentDesc, componentType, 
												user);
		
		System.out.println("MetaDataType : " + compMetaData.getComponentType().getTypeId());            /* Prints 2 */

		em.persist(compMetaData);           /* Throwing Exception here : Unable to persist. Duplicate key entry "1" for key in Component_ID Table... */
		transaction.commit();
		return compMetaData;
	}
	
	@Override
	public ComponentType getComponentTypeByName(String componentTypeName) {
		
		String queryString = "SELECT ct FROM ComponentType ct WHERE " +
								"ct.typeName = '" + componentTypeName + "'";
		Query query = em.createQuery(queryString);
		ComponentType componentType = null;
		
		try {
			componentType = (ComponentType)query.getSingleResult();
		} catch (NoResultException e) {
			return null;
		}
		
		return componentType;
	}

        @Override
	public User getUserByEmail(String email) {
		return em.find(User.class, email);
	}

I have attached my table structure...

Can anyone see, where I am doing anything wrong...
I doubt if I have done the Foreign Key Mapping in the component_meta_data class correct or not..

[James Sutherland]

What is "transaction"? Are you using JTA or JPA transactions?

My guess is you did not find the ComponentType through the same persistence context (EntityManager or transaction).

Try moving the transaction.begin() to the start of the method, and ensure you are using the same EntityManager to find the ComponentType .

[R. Jain]

James Sutherland wrote:What is "transaction"? Are you using JTA or JPA transactions?

My guess is you did not find the ComponentType through the same persistence context (EntityManager or transaction).

Try moving the transaction.begin() to the start of the method, and ensure you are using the same EntityManager to find the ComponentType .

Sorry, I forgot to post init() method.. This method inititializes EntityManager, EntityManagerFactory and EntityTransaction (JPA Transaction).

And anyways, the problem is now resolved.. Thanks for your reply..

Actually the problem was of MySQL Engine. (It was MyISAM and it does not support Foreign Key.. Need to enable InnoDB).
Due to this I was able to insert a value for foreign key which was not in primary key column of ComponentType..