Hibernate Query examples (HQL)

Posted: April 11, 2012 in Uncategorized

Hibernate created a new language named Hibernate Query Language (HQL), the syntax is quite similar to database SQL language. The main difference between is HQL uses class name instead of table name, and property names instead of column name.

HQL is extremely simple to learn and use, and the code is always self-explanatory.

1. HQL Select Query Example

Retrieve a stock data where stock code is “7277″.

Query query = session.createQuery(“from Stock where stockCode = :code “);

query.setParameter(“code”, “7277”);

List list = query.list();

Query query = session.createQuery(“from Stock where stockCode = ‘7277’ “);

List list = query.list();

 2. HQL Update Query Example

Update a stock name to “DIALOG1″ where stock code is “7277″.

Query query = session.createQuery("update Stock set stockName = :stockName" +
                                                 " where stockCode = :stockCode");
query.setParameter("stockName", "DIALOG1");
query.setParameter("stockCode", "7277");
int result = query.executeUpdate();
Query query = session.createQuery("update Stock set stockName = 'DIALOG2'" +
                                                 " where stockCode = '7277'");
int result = query.executeUpdate();

 

3. HQL Delete Query Example

Delete a stock where stock code is “7277″.

Query query = session.createQuery("delete Stock where stockCode = :stockCode");
query.setParameter("stockCode", "7277");
int result = query.executeUpdate();
Query query = session.createQuery("delete Stock where stockCode = '7277'");
int result = query.executeUpdate();

4. HQL Insert Query Example

In HQL, only the INSERT INTO … SELECT … is supported; there is no INSERT INTO … VALUES. HQL only support insert from another table. For example

"insert into Object (id, name) select oo.id, oo.name from OtherObject oo";

Insert a stock record from another backup_stock table. This can also called bulk-insert statement.

Query query = session.createQuery("insert into Stock(stock_code, stock_name)" +
                                     "select stock_code, stock_name from backup_stock");
int result = query.executeUpdate();

The query.executeUpdate() will return how many number of record has been inserted, updated or deleted.

Hibernate parameter binding examples

There are two ways to parameter binding : named parameters or positional.

1. Named parameters

This is the most common and user friendly way. It use colon followed by a parameter name (:example) to define a named parameter. See examples…

Example 1 – setParameter

The setParameter is smart enough to discover the parameter data type for you.

String hql = "from Stock s where s.stockCode = :stockCode";
List result = session.createQuery(hql)
.setParameter("stockCode", "7277")
.list();
Example 2 – setString

You can use setString to tell Hibernate this parameter date type is String.

String hql = "from Stock s where s.stockCode = :stockCode";
List result = session.createQuery(hql)
.setString("stockCode", "7277")
.list();
Example 3 – setProperties

This feature is great ! You can pass an object into the parameter binding. Hibernate will automatic check the object’s properties and match with the colon parameter.

Stock stock = new Stock();
stock.setStockCode("7277");
String hql = "from Stock s where s.stockCode = :stockCode";
List result = session.createQuery(hql)
.setProperties(stock)
.list();

 

2. Positional parameters

It’s use question mark (?) to define a named parameter, and you have to set your parameter according to the position sequence. See example…

String hql = "from Stock s where s.stockCode = ? and s.stockName = ?";
List result = session.createQuery(hql)
.setString(0, "7277")
.setParameter(1, "DIALOG")
.list();

This approach is not support the setProperties function. In addition, it’s vulnerable to easy breakage because every change of the position of the bind parameters requires a change to the parameter binding code.

String hql = "from Stock s where s.stockName = ? and s.stockCode = ?";
List result = session.createQuery(hql)
.setParameter(0, "DIALOG")
.setString(1, "7277")
.list();

 

 

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