The application of Hibernate query--criteria queries with multiple conditions

When querying data, people often need to set query conditions. In SQL or HQL statements, query conditions are often placed in the WHERE clause. In addition, hibernate supports the criteria query, which encapsulates the query criteria as a criteria object. In practical applications, the Createcriteria () method of the session is used to construct a Org.hibernate.Criteria instance, and then the specific query conditions are added to the criteria instance through the Add () method of the criteria. In this way, programmers can query data without using SQL or even hql.

Let's look at a simple example:

Criteria cr = Session.createcriteria (Student.class); Generate a Criteria Object
Cr.add (Restrictionseq ("name", "XY")); Equivalent to where name= ' xy '
List List = Cr.list ();

Let's look at the operator such a comparison.

hql operator	QBC operator	meaning
=	Restrictions.eq ()	equals equal
<>	Restrictions.ne ()	Not equal to not equal
>	RESTRICTIONS.GT ()	Greater than greater than
>=	Restrictions.ge ()	Greater than or equal to greater than or equal
<	Restrictions.lt ()	Less than less than
<=	Restrictions.le ()	Less than or equal to less than or equal
is null	Restrictions.isnull ()	equals null value
is not null	Restrictions.isnotnull ()	Non-null value
like	Restrictions.like ()	String pattern Matching
and	Restrictions.and ()	Logic and
and	Restrictions.conjunction ()	Logic and
or	Restrictions.or ()	Logical OR
or	Restrictions.disjunction ()	Logical OR
not	Restrictions.not ()	Logical non
In (list)	Restrictions.in ()	equals one of the values in the list
Not in (list)	Restrictions.not (restrictions.in ())	is not equal to any one of the values in the list
between x and y	Restrictions.between ()	Any value in XY of closed interval
Not between x and y	Restrictions.not (restrictions. Between ())	Less than value x or greater than value Y

When will the criteria be the most powerful? Is the time for multiple conditional queries.

The view is this:

School Number <input type= "text" name= "Dto.num"/>
Name <input type= "text" name= "Dto.name"/>
<input type= "Submit" value= "Query"/>

we can do this:

Entity Layer

public class Student

{

private int id;

private String name;

Private Date birth;

...........

}

DTO Layer

public class Studentdto
{
private int id; Student number
Private String name;//Student name

public int getId ()
{
return ID;
}

public void setId (int id)
{
This.id = ID;
}

Public String GetName ()
{
return name;
}

public void SetName (String name)
{
THIS.name = name;
}

}

Impl Layer

Public Pagemodel Getqqueryresult (studentdto dto, int start, int pagesize)
{
Criteria C = this.getsession (). Createcriteria (Student.class);
if (0!= dto.getid ())
{
C.add (Restrictions.like ("id", Dto.getid ());
}

if (null!= dto.getname () &&! "". Equals (Dto.getname ()))
{
C.add (Restrictions.like ("XM", "%" + dto.getname () + "%"));
}

int count = C.list (). Size ();
List datas = C.setfirstresult (start). Setmaxresults (pagesize). List ();
int totalpage = Helper.totalpage (count, pagesize);

Get the result set
Pagemodel pm = new Pagemodel ();
Pm.settotal (count);
Pm.setdatas (datas);
Pm.settotalpage (Totalpage);
return PM;
}

....... Here is the knowledge of struts and SSH paging, and there is no more to repeat. ^ ^

Reference Address: http://blog.csdn.net/dengqf/article/details/6603531