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 Post subject: Quote table and column names
PostPosted: Wed Apr 01, 2009 4:08 am 
Newbie

Joined: Wed Nov 26, 2008 5:51 am
Posts: 3
Location: Mannheim
Hi folks,

Yesterday I bumped into the following problem: I've defined an entity called "Constraint". When trying to run my app-server with the hibernate.tablecreation setting on "create", Hibernate complains that there has been a problem with running the create table statement. That is, however, no surprise, as the word constraint is a reserved word in SQL and thus the statement fails. It works fine, when I try to run the statement like "create table `constraint`...". I read somewhere that defining the entity like


Code:
@Entity(name="Constraint")
@Table(name="`Constraint`")
public class Constraint
{
....


will do the trick. However, I am interested in a way to tell Hibernate to always use quotes for table and column names. Is that possible?

Hibernate version:3.2.5.ga


Regards,

Vassil


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 Post subject:
PostPosted: Wed Apr 01, 2009 7:47 am 
Expert
Expert

Joined: Wed Mar 03, 2004 6:35 am
Posts: 1240
Location: Lund, Sweden
I am not 100% sure, but I think that maybe a custom NamingStrategy can do the trick. See http://www.hibernate.org/hib_docs/v3/re ... ategy.html
and http://www.hibernate.org/hib_docs/v3/ap ... ategy.html


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 Post subject:
PostPosted: Wed Apr 01, 2009 8:57 am 
Newbie

Joined: Wed Nov 26, 2008 5:51 am
Posts: 3
Location: Mannheim
You were right! It did the trick! Thanks a lot.

For anyone who might be interested, here's what I did:

1. create a custom naming strategy class:

Code:
package com.mdpframework.dataaccess.hibernate;

import org.hibernate.cfg.DefaultNamingStrategy;
import org.hibernate.dialect.Dialect;

public class DefaultQuotedNamingStrategy extends DefaultNamingStrategy
{
   private static Dialect _dialect = new MySQLInnoDBUTF8Dialect();

   @Override
   public String classToTableName(String className)
   {

      System.out.println("Adding quotes to table from class "+className);
      return addQuotes(super.classToTableName(className));
   }
   
   @Override
   public String tableName(String tableName)
   {
      System.out.println("Adding quotes to table "+tableName);
      return addQuotes(super.tableName(tableName));
   }

   /**
    * Adds opening and closing quotes as provided by the current dialect.
    *
    * @param input
    *          the input to quote
    * @return the qouted input
    */
   private static String addQuotes(String input)
   {
      return new StringBuffer().append(_dialect.openQuote())
                         .append(input)
                         .append(_dialect.closeQuote()).toString();
   }
}


Unfortunately, what I didn't get to work is, load the dialect from the settings. When using
Code:
private static Dialect _dialect = Dialect.getDialect();
I got an exception, telling me there is no dialect set. It's some kind of config issue, as the config says

Code:
   <bean id="hibernateProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
      <property name="properties">
         <props>
            ...
            <prop key="hibernate.dialect">com.mdpframework.dataaccess.hibernate.MySQLInnoDBUTF8Dialect</prop>
            ...
         </props>
      </property>
   </bean>


Usually that works. Aaaanyway

2. Set the naming strategy
Code:
   <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" autowire-candidate="true"  depends-on="hibernateDataSource">
      <property name="dataSource" ref="hibernateDataSource" />
      <property name="hibernateProperties" ref="hibernateProperties" />
      <property name="namingStrategy" ref="namingStrategy"/>
      <property name="configurationClass"><value>org.hibernate.cfg.AnnotationConfiguration</value></property>
      <property name="configLocation"><value>classpath:hibernate.cfg.xml</value></property>
   </bean>

   <bean id="namingStrategy" class="com.movilitas.mdpframework.dataaccess.hibernate.DefaultQuotedNamingStrategy"/>


3. Stop worrying about table names that are SQL reserved words :)

One could extend the above class to also quote column names to use special words for column names as well.

Thanks again!

All the best,
Vassil


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 Post subject:
PostPosted: Wed Apr 01, 2009 9:37 am 
Expert
Expert

Joined: Wed Mar 03, 2004 6:35 am
Posts: 1240
Location: Lund, Sweden
Quote:
Unfortunately, what I didn't get to work is, load the dialect from the settings


Hmmm... I am wondering if the dialect needed...

If you have backticks in the mappings file, Hibernate will convert it to the proper quote character internally, but I don't know if this happens before or after invoking the methods in the NamingStrategy. If the conversion happens after it should be enough for the NamingStrategy to always use backticks.


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 Post subject:
PostPosted: Wed Apr 01, 2009 10:08 am 
Newbie

Joined: Wed Nov 26, 2008 5:51 am
Posts: 3
Location: Mannheim
Hm, interesting point.

I guess it's even the right way to do this, as it's simpler and cleaner.

So the class would be:

Code:
package com.mdpframework.dataaccess.hibernate;

import org.hibernate.cfg.DefaultNamingStrategy;

public class DefaultQuotedNamingStrategy extends DefaultNamingStrategy
{

   @Override
   public String classToTableName(String className)
   {
      return addQuotes(super.classToTableName(className));
   }
   
   @Override
   public String tableName(String tableName)
   {
      return addQuotes(super.tableName(tableName));
   }

   /**
    * Adds backticks before and after the name.
    *
    * @param input
    *          the input to quote
    * @return the quoted input
    */
   private static String addQuotes(String input)
   {
      return new StringBuffer().append('`')
                         .append(input)
                         .append('`').toString();
   }
}


Regards,
Vassil


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