HELP !! problem with setparameter in entitymanager

[jim li]

filterName = "first"

Query q = em.createQuery( "From UserInfo where :filterName like 'jim'");
q.setParameter("filterName", filterName);
q.getResultList();
my reuslt returns nothing to me.

however, if i use
Query q = em.createQuery( "From UserInfo where first like 'jim'");
q.setParameter("filterName", filterName);
q.getResultList();
i got the result i want

please help me!!!

[Mark Spritzler]

Parameters are for values, not field names.

You are trying to set which field is checked, rather than a field being checked by different values.

You can use a parameter to parameter "jim" the value, but not "first" the field.

Mark

[jim li]

thank you for you help

could you please give me couple of example?

i really appreciate your help

[jim li]

firstName = "first"
first is the column in my database.
if i set the parameter to 'jim' instead of "first"

how could i know which column it is

[jim li]

thank you

it works now

[Cameron Wallace McKenzie]

As Mark said, the whole point of variable injection is to inject a value into the variable being used. Here's a hard coded query example:

Session session = HibernateUtil.beginTransaction();
String hql="from User where loginName = 'mj' ";
Query query = session.createQuery(hql);
Object o  = query.uniqueResult();
User u = (User)o;
System.out.println(u.getLoginName());
System.out.println("\n\n");
HibernateUtil.commitTransaction();    

Notice the line of code:

String hql="from User where loginName = 'mj' ";

'mj' is the varible name. To do variable injection, you would replace the 'mj' with a variable. It might look like this:

 
String loginName;
/*obtain the loginName from user somehow!!!*/ 
String sqlQuery = 
          "select * from user where loginName = ?";
PreparedStatement ps = con.prepareStatement(sqlQuery);
/*replace the first ? mark 
with the value held by the variable*/
ps.setString(1, loginName);
ResultSet rs = ps.executeQuery();

As you can see, you were pretty close. You inject the variable name, not the column name/property name.

-Cameron McKenzie