{"id":599,"date":"2004-06-01T12:30:46","date_gmt":"2004-06-01T16:30:46","guid":{"rendered":"http:\/\/wordpress.cephas.net\/?p=599"},"modified":"2004-06-01T12:30:46","modified_gmt":"2004-06-01T16:30:46","slug":"hibernate-deleting-objects","status":"publish","type":"post","link":"https:\/\/cephas.net\/blog\/2004\/06\/01\/hibernate-deleting-objects\/","title":{"rendered":"Hibernate: Deleting Objects"},"content":{"rendered":"

It might look like this is turning into a Hibernate blog… maybe it’s just a phase I’m going through. This last week I ran into a place in some code where I wanted to write a query to delete a number of rows from the database. Deleting a single row using Hibernate is simple; get an instance of the persistent object you want to delete (ie: a Book, etc..) and an instance of the Session<\/a> object and then called the delete(Object)<\/a> method:
\n
\nlong bookid = 12;
\nSession sess = HibernateFactory.currentSession();
\nObject book = sess.load(Book.class, bookid);
\nsess.delete(book);
\n<\/code>
\nEasy. Now, if you wanted to delete all the computer books for some reason, you’d have to first query the database using Hibernate to get a Collection<\/a> of books, then iterate over the books, calling delete(Object object) on each one.
\n
\nCollection books = BookFactory.getComputerBooks();
\nSession sess = HibernateFactory.currentSession();
\nfor (Iterator i = books.iterator(); i.hasNext();) {
\n  Book book = (Book)i.next();
\n  sess.delete(book);
\n}
\n<\/code>
\nIt’s easier than that though. The Session object has a delete(String query)<\/a> method that I originally thought took a standard SQL ‘delete from table where…’ statement. After fussing with it for a bit, I read the documentation which says: “Delete all objects returned by the query. Return the number of objects deleted.”. Aha! Instead of calling delete() on each one, you use a SQL (or a HQL) statement that fetches the objects and then pass the results directly to the delete method:
\n
\nSession sess = HibernateFactory.currentSession();
\nsess.delete(\"select book FROM org.mycompany.Book as book where type = 'technical'\");
\n<\/code>
\nJust another example of how Hibernate makes it easier to work with relational databases.<\/p>\n","protected":false},"excerpt":{"rendered":"

It might look like this is turning into a Hibernate blog… maybe it’s just a phase I’m going through. This last week I ran into a place in some code where I wanted to write a query to delete a number of rows from the database. Deleting a single row using Hibernate is simple; get … Continue reading Hibernate: Deleting Objects<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/posts\/599"}],"collection":[{"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/comments?post=599"}],"version-history":[{"count":0,"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/posts\/599\/revisions"}],"wp:attachment":[{"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/media?parent=599"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/categories?post=599"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cephas.net\/blog\/wp-json\/wp\/v2\/tags?post=599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}