Six ways to Hibernate queries

Hibernate query Six ways are hql query, Object query criteria method, dynamic query Detachedcriteria, example query, SQL query, named query .

If you simply use Hibernate to query the database only need to understand one of them can accomplish the general functions you want to achieve, but to learn more knowledge on the six methods, they provide more choices. Of course, each method has its own applicable conditions and prerequisites.

1, HQL Query

HQL is Hibernate's own set of query languages, different from SQL syntax, with the advantages of cross-database. Example code:

[Java]View Plain Copy

2. static void query (String name) {
4. Session s=null;
6. try{
8. S=hibernateutil.getsession ();
12. //from is followed by an object, not a table name
14. String hql="from admin as admin where admin.aname=:name";   Using named parameters, it is recommended to use, easy to read.
16. Query query=s.createquery (HQL);
18. Query.setstring ("name", name);
22. List<admin> list=query.list ();
26. For (Admin admin:list) {
28. System.out.println (Admin.getaname ());
30. }
32. }finally{
34. if (s!=null)
36. S.close ();
38. }
40. }

Application: Common method, more traditional, similar to JDBC. Cons: New query Language, limited applicability, applies only to hibernate framework.

2, the object of query criteria method :

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2. static void Cri (String name,string password) {
4. Session s=null;
6. try{
8. S=hibernateutil.getsession ();
12. Criteria C=s.createcriteria (Admin.   Class);
14. C.add (Restrictions.eq ("Aname", name)); EQ is equal to, GT is greater than, LT is less than, or is or
16. C.add (Restrictions.eq ("Apassword", password));
20. List<admin> list=c.list ();
22. For (Admin admin:list) {
24. System.out.println (Admin.getaname ());
26. }
28. }finally{
30. if (s!=null)
32. S.close ();
34. }
36. }

Application: Object-oriented operation, innovation of the previous database operation mode, easy to read. Disadvantage: The application surface is more limited than HQL.

3, dynamic separation query Detachedcriteria

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1. Static List DC (Detachedcriteria DC) {
3. Session s = hibernateutil.getsession ();
4. Criteria C = Dc.getexecutablecriteria (s);
5. List rs = c.list ();
6. S.close ();
7. return RS;
8. }

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2. Detachedcriteria DC = Detachedcriteria.forclass (User.   Class);
4. int id = 1;
6. if (id! = 0)
8. Dc.add (Restrictions.eq ("id", id));
10. Date age = new Date ();
12. if (age! = null)
14. Dc.add (Restrictions.le ("Birthday", age));
16. List users = DC (DC);
18. SYSTEM.OUT.PRINTLN ("offline query returns results:" + users);

Application: Object-oriented operations, separation of business and the underlying, do not require the field attribute ingestion to the DAO implementation layer. Disadvantage: The application surface is more limited than HQL.

4. Example Query

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1. static list example (user user)  {  
2.   session s = hibernateutil.getsession ();   
3.   list<user> users = s.createcriteria (User.class). Add (  
4.     example.create (user)). List ();   
5.   //&NBSP;LIST<USER>&NBSP;&NBSP;
6.   // users2=s.createcriteria (user.class). Add (Example.create ( User). IgnoreCase ())   
7.   //&NBSP;. Createcriteria ("Child"). Add ((example.create (user))). List ();   
8.   return users;  
9. &NBSP;}&NBSP;&NBSP;

Where applicable: Object-oriented operation. Disadvantage: The applicable surface is more limited than HQL, not recommended.

5. SQL query

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1. static List SQL () {
3. Session s = hibernateutil.getsession ();
4. Query q = s.createsqlquery ("SELECT * from User"). Addentity (user.   Class);
5. List<user> rs = q.list ();
6. S.close ();
7. return RS;
8. }

Application: Not familiar with hql friends, and do not intend to transfer database platform friends, omnipotent method shortcomings: the destruction of cross-platform, difficult to maintain, not object-oriented.

6. Named query

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1. Static List namedquery (int id) {
2. Session s = hibernateutil.getsession ();
3. Query q = s.getnamedquery ("Getuserbyid");
4. Q.setinteger ("id", id);
5. return q.list ();
6. }

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2. <?xml version="1.0" encoding="Utf-8"?>
4. <! DOCTYPE hibernate-mapping public "-//hibernate/hibernate mapping DTD 3.0//en"
6. "Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
12. <class Name="Com.sy.vo.User" table= "User" catalog="News" >
20. </class>
22. <!--named queries: Defining query Conditions--
24. <query name="Getuserbyid" >
26. <! [Cdata[from User where id=:id]]>
28. </query>
30. < using SQL in!--named queries, deprecated, affecting cross-database
32. <sql-query name="GetUserById2" >
34. <! [Cdata[select * from User where]]>
36. </sql-query>

Six ways to Hibernate queries