Inheritance ing of Hibernate association relationship ing and hibernate Association

Inheritance ing of Hibernate association relationship ing and hibernate Association

First, an Article class (Article) contains attributes such as id, title, content, and postTime.

package entity;import java.util.Date;public class Article {private Integer id;private String title;private String content;private Date postTime;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}public Date getPostTime() {return postTime;}public void setPostTime(Date postTime) {this.postTime = postTime;}}

Then let's look at its sub-classes, Topic classes and Reply classes. Apart from the attributes of the parent class, they also have their own unique attributes.

package entity;public class Topic extends Article{private int type;public int getType() {return type;}public void setType(int type) {this.type = type;}}

package entity;public class Reply extends Article{private int floor;public int getFloor() {return floor;}public void setFloor(int floor) {this.floor = floor;}}

There are three methods to inherit ing:

Method 1: store the information of the parent class and Child class in the same table. Then, there is a field in the data table to indicate the type of the record. The unique attribute of the Child class can be null. Let's take a look at the ing configuration file.

<? Xml version = "1.0" encoding = "UTF-8"?> <! DOCTYPE hibernate-mapping PUBLIC "-// Hibernate/Hibernate DTD ing DTD 3.0 // EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 
Method 2: the parent class and subclass are not in the same table, and each class has a table. The abstract class corresponds to a table. This is the configuration subclass using joined-subclass.
<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
Method 3: each class has a separate table, and the abstract class does not correspond to a table. The database table corresponding to the subclass corresponds to all attributes, including information inherited from the parent class.
<? Xml version = "1.0" encoding = "UTF-8"?> <! DOCTYPE hibernate-mapping PUBLIC "-// Hibernate/Hibernate DTD ing DTD 3.0 // EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 
Then let's take a look at the test classes. The three methods are the same. Only the save methods in method 3 cannot store the information of their parent classes because the abstract classes do not have separate data tables.
Package test; import org. hibernate. session; import org. hibernate. transaction; import entity. article; import entity. reply; import entity. topic; import factory. hibernateSessionFactory; public class Test {private Session session = null; private Transaction tran = null; @ org. junit. testpublic void save () {session = HibernateSessionFactory. getSession (); tran = session. beginTransaction (); try {Article article = new Article (); article. setId (1); article. setTitle ("this is an Article"); Topic topic = new Topic (); topic. setId (2); topic. setTitle ("this is a Topic"); Reply reply = new Reply (); reply. setId (3); reply. setTitle ("this is a reply"); session. save (article); session. save (topic); session. save (reply); tran. commit ();} catch (Exception e) {tran. rollback () ;}@ org. junit. testpublic void Get () {session = HibernateSessionFactory. getSession (); tran = session. beginTransaction (); try {Article a = (Article) session. get (Article. class, 1); Topic t = (Topic) session. get (Topic. class, 2); Reply r = (Reply) session. get (Reply. class, 3); System. out. println (. getTitle (); System. out. println (t. getTitle (); System. out. println (r. getTitle (); tran. commit ();} catch (Exception e) {tran. rollback ();}}}

 

Inheritance relationship ing in hibernate
First, the primary key entity in the foreign key must be manually initialized (new primary key entity ())
Configuration saves time by adding fetch = "join" to the properties of <fail-to-one> and <set>"
In addition, only by searching for the hibernate primary key in hibernate will the entities in the foreign key be automatically assigned a value to the set in the primary key.

How to Implement hibernate relationship ing and inheritance? What is the concept?
* 1) the parent class and subclass have corresponding tables. Use <joined-subclass> to define the inheritance relationship. The procedure is as follows:
A. Generate a basic ing between the parent table and the child table for a single table
B. Add a subclass TO THE extends parent class.
C. Use <joined-subclass> to define subclass ing
From the version of Hibernate3.0, you can extract <joined-subclass> and put it in an hbm. xml file. The format is as follows:
<Hibernate-mapping>
<Joined-subclass name = "subclass type"
Extends = "parent class type"
Table = "subclass table">
<Key column = "subtable join field"/>
// Property field ing
</Joined-subclass>
</Hibernate-mapping>
* 2) the parent class and subclass use the same data table.

Multiple choice questions:
Number, question, difficulty, option, and answer
Short answer:
Number, question, difficulty, and answer
Data Table Question
Number, question, difficulty, option, answer selection, answer, question type
Use <subclass> to define subclass ing. The procedure is as follows:
A. Modify the object class and define it as the structure of the parent class and subclass.
B. Define the ing in the ing File
<Hibernate-mapping>
<Class name = "parent type" table = "data table">
// Define the ing of attributes in the parent class
<Discriminator column = "differentiate fields"/>
<Subclass name = "subclass 1"
Discriminator-value = "zone score">
// Define the ing of attributes in subclass 1
</Subclass>
<Subclass name = "subclass 2"
Discriminator-value = "zone score">
// Define the ing of attributes in subclass 2
</Subclass>
</Class>
<Hibernate-mapping>

The above two types of inheritance relationship ing. Note that the ing configured in <joined-subclass> corresponds to two tables and two entity classes. The IDS of the two tables must be one-to-one, that is, the same id represents a physical object, and another one defines the ing. Even if you use hibernate for query ...... remaining full text>