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Hibernate – receptár tipov a trikov

 2 years ago
source link: https://novotnyr.github.io/scrolls/hibernate-receptar-tipy-triky/
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Hibernate – receptár tipov a trikov

Hibernate – receptár tipov a trikov

2008/02/19

Interceptory

package sk.annun.davano.dao;

import java.util.Collections;
import java.util.Iterator;

import org.apache.log4j.Logger;
import org.hibernate.EmptyInterceptor;
import org.springframework.jdbc.core.JdbcTemplate;

import sk.annun.davano.Post;

public class FulltextSearchUpdateInterceptor extends EmptyInterceptor {
  
  public static final Logger logger = Logger.getLogger(FulltextSearchUpdateInterceptor.class);

  private JdbcTemplate jdbcTemplate;
  
//  @Override
//  public boolean onFlushDirty(Object entity, Serializable id, Object[] currentState, Object[] previousState, String[] propertyNames, Type[] types) {
//    if(entity instanceof Post) {
//      Object[] params = {getText((Post) entity), id};
//      jdbcTemplate.update("UPDATE post_fulltext SET text = ? WHERE id = ?", params);
//    }
//    return false;
//  }

//  @Override
//  public boolean onSave(Object entity, Serializable id, Object[] state, String[] propertyNames, Type[] types) {
//    if(entity instanceof Post) {
//      Object[] params = {id, getText((Post) entity)};
//      jdbcTemplate.update("INSERT into post_fulltext VALUES(?, ?)", params);  
//    }
//    return false;
//  }
  
//  @Override
//  public void postFlush(Iterator entities) {
//    synchronized(this) {
//      while(entities.hasNext()) {
//        Object entity = entities.next();
//        System.err.println(entity);
//      }
//    }
//  }
  
  protected String getText(Post post) {
    StringBuilder fulltextData = new StringBuilder();
    fulltextData.append(post.getTitle()).append(" ").append(post.getText());
    fulltextData.append(post.getStory().getTitle()).append(" ").append(post.getStory().getDescription());
    return fulltextData.toString();
  }

  public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
    this.jdbcTemplate = jdbcTemplate;
  }
  
  
}

Problémy:

  • onSave() sa volá pred uložením objektu. V prípade MySQL nemusí mať entita ešte pridelený primárny kľúč
  • onFlushDirty() počas behu flush()
  • postFlush() po dobehnutí flush(). Problém môže byť v tom, že prechádzanie iterátora entít nie je thread-safe a môže vyvolať ConcurrentModificationException, čo znemožňuje dosiahnutie cieľa.

Deklarácia interceptora v Springu

<bean id="sessionFactory"              
      class="org.springframework.orm.hibernate3.
                 annotation.AnnotationSessionFactoryBean">
  <property name="entityInterceptor">
    <bean class="dao.FulltextSearchUpdateInterceptor">
      <property name="jdbcTemplate" ref="jdbcTemplate" />           
    </bean>
  </property>
</bean>

Udalosti

public class FulltextSearchUpdateListener implements PostInsertEventListener, PostUpdateEventListener {
  private JdbcTemplate jdbcTemplate;
  
  public void onPostInsert(PostInsertEvent event) {
    if(event.getEntity() instanceof Post) {
      Post post = (Post) event.getEntity();
      Object[] params = {post.getId(), getText(post)};
      jdbcTemplate.update("INSERT into post_fulltext VALUES(?, ?)", 
                          params);
    }
  }

  public void onPostUpdate(PostUpdateEvent event) {
    if(event.getEntity() instanceof Post) {
      Post post = (Post) event.getEntity();

      Object[] params = {getText(post), post.getId()};
      jdbcTemplate.update("UPDATE post_fulltext SET text = ? " +
                          "WHERE id = ?", params);
    }
  }
  
  private String getText(Post post) {
    //..
  }

}

Deklarácia v Springu

<bean id="sessionFactory"              
      class="org.springframework.orm.hibernate3.
                 annotation.AnnotationSessionFactoryBean">
  <property name="eventListeners">
    <map>
      <entry key="post-update" 
             value-ref="hibernateFulltextListener" />
      <entry key="post-insert" 
             value-ref="hibernateFulltextListener" />
  </map>
</property>
</bean>

V mape je treba uviesť aj hibernateovské implicitné listenery, alebo oddediť od defaultných listenerov (MySaveOrUpdateListener extends DefaultSaveOrUpdateListener). Inak sa môže odstaviť základná funkcionalita (keďže tá je tiež riešená listenermi). Kľúče do mapy je možné nájsť v DTD súbore hibernate-configuration. Platí pravidlo, že pre stringový kľúč treba namapovať listener s daným interfejsom. Napr. post-update -> PostUpdateEventListener.


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