ID of many-to-one relation

Myk · **Joined:** Sun Jan 04, 2004 2:46 pm **Posts:** 147

Is there any way of retrieving a foreign key in a table without hitting the database for the table the foreign key relates to?

ie

Code:

<hibernate-mapping>
    
    <class 
        name="eg.BlogItem" 
        table="BLOG_ITEMS" 
        dynamic-update="true"
        lazy="true">
        
        <id 
            name="id" 
            column="BLOG_ITEM_ID">
            
            <generator class="native"/>
            
        </id>
        
        <property 
            name="title" 
            column="TITLE" 
            not-null="true"/>
            
        <property 
            name="text" 
            column="TEXT" 
            not-null="true"/>
            
        <property 
            name="datetime" 
            column="DATE_TIME" 
            not-null="true"/>
            
        <many-to-one 
            name="blog" 
            column="BLOG_ID" 
            not-null="true"/>
            
    </class>
    
</hibernate-mapping>

with class definition

Code:

package eg;

import java.text.DateFormat;
import java.util.Calendar;

public class BlogItem {
    private Long _id;
    private Calendar _datetime;
    private String _text;
    private String _title;
    private Blog _blog;

    public Blog getBlog() {
        return _blog;
    }
    public Calendar getDatetime() {
        return _datetime;
    }
    public Long getId() {
        return _id;
    }
    public String getText() {
        return _text;
    }
    public String getTitle() {
        return _title;
    }
    public void setBlog(Blog blog) {
        _blog = blog;
    }
    public void setDatetime(Calendar calendar) {
        _datetime = calendar;
    }
    public void setId(Long long1) {
        _id = long1;
    }
    public void setText(String string) {
        _text = string;
    }
    public void setTitle(String string) {
        _title = string;
    }
}

I would just like to get the actual content of the Blog column from a BlogItem rather than going BlogItem.getBlog().getId() which will persist Blog from the database which is unecessary as I only want the id which will be the foreign key in the BlogItem table. Assume lazy initialisation is being used.

Cheers.

Myk.

emmanuel · **Posted:** Sun Jan 04, 2004 4:46 pm

Either

Code:

<property name="blogId" column="BLOG_ID" insert="false" update="false"

or proxy the Blog class. Id return won't load blog from db

Code:

<class
        name="eg.Blog"
        table="BLOG" lazy="true"> 

Myk · **Joined:** Sun Jan 04, 2004 2:46 pm **Posts:** 147

Thanks for the quick reply :)

The second solution is what I am after.

Just curious but does the first solution now have two "blog id" columns, one created by that property, and the other implicitly by the many-to-one relation tag?

emmanuel · **Posted:** Sun Jan 04, 2004 5:08 pm

Nope, same column name prevent duplication and insert and update = false means this is a read only property : no concurrent modification from 2 java properties. Actually, if you don't set the 2 attributes to false, Hibernate will consider the mapping false.

Myk · **Joined:** Sun Jan 04, 2004 2:46 pm **Posts:** 147

Gotcha.

Thanks again.