Heap exception while loading complete table data from database

[Matt Josh]

Hi

In my project I am using JPA.
Recently we have created JPA pojo from existing Tables in schema using JPA Entities from Table tool.
Now I am using Spring JpaDaoSupport at DAO layer.
I started with simple query to fetch POJO based on primary key that works fine.
when I try to fetch all data for given entity it throws heap error.
My entity as strucuture something like this.

@Entity
@Table(name="tbl_example",schema="sch_e")
public class Entity implements Serializable {
	private static final long serialVersionUID = 1L;

	@Id
	@Column(name="pk", unique=true, nullable=false, precision=10)
	private long  id;

	@Column(name="DATA_STATUS", length=10)
	private String dataStatusCd;

	@Column(name="C1", length=32)
	private String c1;
  
	@Column(name="C2", length=8)
	private String c2;

	@Column(name="C3", length=8)
	private String c3;


	//bi-directional many-to-one association to Entity2
	@OneToMany(mappedBy="entity",fetch = FetchType.LAZY)
	private Set<Entity2> entities2;

	//bi-directional many-to-one association to Entity3
	@OneToMany(mappedBy="entity",fetch = FetchType.LAZY)
	private Set<Entity3> entities3;
	
	//bi-directional many-to-one association to Entity4
	@OneToMany(mappedBy="entity",fetch = FetchType.LAZY)
	private Set<Entity4> entities4;
	
	//bi-directional many-to-one association to Entity5
	@OneToMany(mappedBy="entity",fetch = FetchType.LAZY)
	private Set<Entity5> entities5

	//... getter and setter for attributes
	
	}

Please suggest if I can implemenet some kind of lazy initialization to avoid heap issue

From DAO I have simple query like
Public EntityDao extends JpaDaoSupport{
getEntities(){
List<Entity> entites = getJpaTemplate().find("from Entity");
}
}

I am very new to JPA based implementation request you to please give suggestion on initialization and load strategy.

Matt

[Paul Sturrock]

You are already using lazy initialization. Could it be that you just don;t have enough heap space to load all Entity records?

[Matt Josh]

Is it possible to set Lazy loading for OneToOne mapping ojects?

[Paul Sturrock]

Yes, but you are not using OneToOne mappings?

[Matt Josh]

In database I have 207306 rows for Entity as part of process I have to read all this data and put to some cache.
Is it possible to implement some kind of paging or slicing which automatically fetch x number of rows get result which I can save in cache
again make call to get fix number of data.

[Paul Sturrock]

Do you have to put all 207306 rows in the cache? If so, paging will not help - you need a much bigger heap or a disk based cache.