Hibernate Learning Series-----(9) Hibernate map Collection of the operation of set properties

As usual, create a new Studentmap.java entity class and store the hobby attribute using the Map collection interface:

 Packagecom.joe.entity;ImportJava.util.Map; Public classStudentmap {Private intID; PrivateString name; Private intAge ; PrivateMap<string,string>Hobby; /*** No parameter constructor*/     PublicStudentmap () {} Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     Public intGetage () {returnAge ; }     Public voidSetage (intAge ) {         This. Age =Age ; }     PublicMap<string, string>Gethobby () {returnHobby; }     Public voidSethobby (map<string, string>Hobby) {         This. Hobby =Hobby; }            }

The next step is to configure the object-relational mapping file, which can be configured in hibernate using the <map> tag, and first look at the common properties and sub-elements of the <map> tag bar:<map> Elements are used to map properties of the Java.util.Map type, and commonly used properties and child elements are:

1. Name property
2. Table Property
3. <key> child elements
4. <map-key> child elements
5. <element> child elements

In Java, the Map collection interface holds data in the form of a key-value pair, so <map-key> is the key to the map, so it also requires additional columns to hold the key values. The content in StudentMap.hbm.xml is:

<?XML version= "1.0" encoding= "UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "Http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping>    <!--a class tag corresponds to an entity class, the name attribute specifies the entity class name, and the table property specifies the associated database table -    <classname= "Com.joe.entity.StudentMap"Table= "Stu_map_tab">        <!--PRIMARY Key -        <IDname= "id"column= "stu_id">            <!--the policy of providing ID increment native will be judged by the database itself -            <Generatorclass= "Native"></Generator>        </ID>        <!--other properties, name corresponding to the attribute of the entity class, column corresponding to the relational database table -        < Propertyname= "Name"column= "Stu_name"></ Property>        < Propertyname= "Age"column= "Stu_age"></ Property>                <Mapname= "Hobby"Table= "Hobby_map_tab">            <Keycolumn= "student_id"></Key>            <Map-keycolumn= "KeyColumn"type= "string"></Map-key>            <elementtype= "string"column= "Hobby"></element>        </Map>            </class></hibernate-mapping>

Finally paste the code of the Studentmaptest.java class, this test and the previous several articles in the same test, it does not show one by one:

 Packagecom.joe.test;ImportJava.util.HashMap;ImportJava.util.Map;Importorg.hibernate.HibernateException;Importorg.hibernate.Session;Importorg.hibernate.Transaction;Importorg.hibernate.cfg.Configuration;ImportOrg.hibernate.tool.hbm2ddl.SchemaExport;Importorg.junit.Test;ImportCom.joe.entity.StudentMap;Importcom.joe.util.HibernateUtils; Public classstudentmaptest {@Test Public voidcreatetable () {Configuration cfg=NewConfiguration (). Configure (); Schemaexport SE=NewSchemaexport (CFG); Se.create (true,true); } @Test Public voidSave () {Transaction tx=NULL; Session Session=NULL; Try{Session=hibernateutils.getsession (); TX=session.begintransaction (); Studentmap Stu=NewStudentmap (); Stu.setname ("Wangwu"); Stu.setage (20); @SuppressWarnings ({"Unchecked", "Rawtypes"}) Map<String,String> map=NewHashMap (); Map.put ("A", "Run"); Map.put ("B", "Eat");                        Stu.sethobby (map);                                    Session.save (Stu);        Tx.commit (); }Catch(Hibernateexception He) {if(tx!=NULL) {tx.rollback ();        } he.printstacktrace (); }finally{hibernateutils.closesession (session); }} @Test Public voidFindAll () {Transaction tx=NULL; Session Session=NULL; Try{Session=hibernateutils.getsession (); TX=session.begintransaction (); Studentmap Stu= (Studentmap) session.get (Studentmap.class, 1); System.out.println (Stu.getid ()+stu.getname () +stu.getage ()); Map<string,string > map=Stu.gethobby ();            SYSTEM.OUT.PRINTLN (map);        Tx.commit (); }Catch(Hibernateexception He) {if(tx!=NULL) {tx.rollback ();        } he.printstacktrace (); }finally{hibernateutils.closesession (session); }    }}

Hibernate on the operation of the collection is written here, in fact, there are many did not write, if there is a great God read my article, hope that a lot of guidance, finally, about the Java collection of learning, I saw in the garden has a garden friends wrote a series, feel write very good, suggest you look, Java collection series Directory (Category)

Hibernate Learning Series-----(9) Hibernate map Collection of the operation of set properties