Hello, I'm trying to determine if there is an annotation or mapping that I can apply to my objects in order to persist my entity. The entity contains a number of values that map easily to the database. However, the entity also contains a collection of key-value attributes that are stored in a list. The classes at listed below. The DB table looks something like this:

create table entity
(id int,
name varchar(50),
keyA varchar(50),
keyB varchar(50),
keyC varchar(50))

I would like to do something like this:
Entity e = new Entity();
e.setName("name");
e.setAttribute("keyA", "valueA");
e.setAttribute("keyB", "valueB");
e.setAttribute("keyC", "valueB");

entityManager.persist(e);

Is there an entity mapping that I can apply to my objects to persist the entity? I know that it would be easy to add an attribute table and have a one-to-many mapping, but this DB schema would not really allow efficient query on the 3 key values.

Thanks for your help.

public class Entity
{
private int id;
private String name;
private List<Attribute> attributeList;

public int getId()
{
return id;
}

public void setId(int id)
{
this.id = id;
}

public String getName()
{
return name;
}

public void setName(String name)
{
this.name = name;
}

public void setAttribute(String key, String value)
{
if (attributeList == null)
{
attributeList = new ArrayList<Attribute>();
}
Attribute attr = new Attribute();
attr.setKey(key);
attr.setValue(value);
attributeList.add(attr);
}

}


public class Attribute
{
private String key;
private String value;

public String getKey()
{
return key;
}

public void setKey(String key)
{
this.key = key;
}

public String getValue()
{
return value;
}

public void setValue(String value)
{
this.value = value;
}

}

Hi weeznat


Adding an Attribute table is the first solution to think of. You should always use a normalized DB schema. It is reliable and efficient.

Another option would be to get rid of the List<Attribute> field. If you will always have precisely these three keys you could exchange the List<Attribute> for three fields of type Attribute. The Attribute entity would then have to be mapped as a Component.

In both cases, you would still be able to use your setAttribute(String key, String value) methods.

CU
Froestel

Thanks for your quick response. We've decided to remove the list as you suggested.