The mapping relationship of hibernate

1 Collection Mappings

One buyer corresponds to multiple addresses

Configuration of the Set collection

<!--The next thing we should configure is our set of collection mappings set--

<set name= "Addresses" table= "t_address" >

<!--This key is equivalent to configuring a foreign key so this foreign key is automatically mapped to the current class's primary key--

<!--this u_id will automatically map to the ID value of the primary key above--

<key column= "u_id" ></key>

<!--The following column is dedicated to storing addresses

Keep in mind that because it is a collection, the data type of the data in the collection must be written or otherwise error

-

<element column= "Address" type= "java.lang.String" ></element>

</set>

List collection Configuration

<!--The next thing we should configure is our collection map list--

<list name= "Addresses" table= "T_address_list" >

<!--is configured with our foreign key--

<key column= "u_id" ></key>

<!-- here is the Set Set unique difference The following configuration represents a sorted column -

<list-index column= "Indexs" ></list-index>

<!--is configured with a real-mapping field--

<element column= "Address" type= "java.lang.String" ></element>

</list>

Configuration of the Map collection

<!--Here's a map of the map collection--

<map name= "Addresses" table= "T_address_map" >

<key column= "u_id" ></key>

<map-key column= "keys_001" type= "java.lang.String" ></map-key>

<element column= "Address" type= "java.lang.String" ></element>

</map>

Attention:

The first thing to do when using a set map is to master the data types that must be given to the data in the collection otherwise error

2--in using our list collection is the time to give our list collection a sorted column (required)

3--you need to add a mapping field for the key in the collection mapping table when using the Map collection

4--in the collection <key></key> this represents the key that the collection is referencing, and the foreign key is the auto-complete mapping

The foreign key is actively mapped to the primary key of our entity.

One-to-many mapping configuration file:

<!--is configured with a one-to-many collection map--

<set name= "Emps" table= "T_employee" cascade= "Save-update,delete" >

The foreign keys in the <!--collection are automatically mapped to the primary key above--

<key column= "dept_id" ></key>

<one-to-many class= "employ"/>

</set>

2-to-one mapping configuration file:

<many-to-one name= "Dept" class= "dept" column= "dept_id" ></many-to-one>

Note: The actual development does not require both sides of the configuration, and generally in practice are more maintenance one

cascading issues Cascade

<set name= "Emps" table= "T_employee" cascade= "Save-update" >

The foreign keys in the <!--collection are automatically mapped to the primary key above--

<key column= "dept_id" ></key>

<one-to-many class= "employ"/>

</set>

CASCADE: Cascade Cascade with three types: Save and update save-update cascade Delete all (the union of the first two guys)

Cascading saves and updates are available, but in the development of the general situation of the lower-level deletion is not used because he will affect more than one table

4 Many-to-many association mappings

A programmer can develop multiple project programmers-----> projects (one-to-many relationships)

A project is developed by multiple developers-----> Programmers (one-to-many relationships)

In summary, two one-to-many relationships constitute a many-to-many relationship

The configuration of one side of project

<!--is configured with many-to-many collection mappings--

<set name= "Devs" table= "t_relation" cascade= "All" >

<!--This key you remember is the primary key to the current class of the map--

<key column= "pro_id" ></key>

<!--is configured with another table associated with it

Column: Configures the name of this value that the other's primary key maps in the relational table

Class: Configure the name of the other person

-

<many-to-many column= "dev_id" class= "Developer" ></many-to-many>

</set>

Configuration of the Developer party

<!--is configured with many-to-many collection mappings--

<set name= "Pros" table= "t_relation" cascade= "All" >

<!--This key you remember is the primary key to the current class of the map--

<key column= "dev_id" ></key>

<!--is configured with another table associated with it

Column: Configures the name of this value that the other's primary key maps in the relational table

Class: Configure the name of the other person

-

<many-to-many column= "pro_id" class= "Project" ></many-to-many>

</set>

5 Inheritance Mappings

1 Common Inheritance Mappings

Requirements: Now there are animals (animal this class) and the dog class and fish This class requires the use of inheritance mappings to complete the configuration of this association relationship

<class name= "Dog" table= "T_dog" >

<!--configuration is the primary key---in the table

<id name= "id" type= "Java.lang.Integer" >

<generator class= "Native" >

</generator>

</id>

<!--is configured for normal columns--

<property name= "Color" ></property>

<property name= "Name" ></property>

<property name= "num" ></property>

</class>

2 All self-class parent classes correspond to a single table

Classification: First there must be a classification only after the classification then this will know who is the data

The fields of the table should contain all the fields

<class name= "Animal" table= "t_animal_01" >

<!--configuration is the primary key---in the table

<id name= "id" type= "Java.lang.Integer" >

<generator class= "Native" >

</generator>

</id>

<!--Configure a non-public

<!--the first of the entire classification

Here's the column for the classification.

-

<discriminator column= "Type_" length= "$" type= "string" ></discriminator>

<!--is configured for normal columns--

<property name= "Color" ></property>

<property name= "Name" ></property>

<!--to configure our dog and fish separately--

<subclass name= "Dog" discriminator-value= "Dog_" >

<!--want to configure this child with a type--

<property name= "num" type= "string" ></property>

</subclass>

<!--configuring Fish--

<subclass name= "Fish" discriminator-value= "Fish_" >

<property name= "Fishcoatcount" type= "Java.lang.Integer" ></property>

</subclass>

</class>

3 All classes correspond to tables

1>: To implement the sub-table then the first thing to do is to anianl the primary key from the growth to me changed ...

2>: Using the Join-class to complete the sub-table

<class name= "Animal" table= "t_animal_02" >

<!--configuration is the primary key---in the table

<id name= "id" type= "string" >

<generator class= "Assigned" >

</generator>

</id>

<!--is configured for normal columns--

<property name= "Color" ></property>

<property name= "Name" ></property>

<!--the next step is to configure our sub-table--

<joined-subclass name= "Dog" table= "t_dog_02" >

<!--the key here automatically maps to the primary key of the class above--

<key column= "id" ></key>

<!--is configured with other columns--

<property name= "num" ></property>

</joined-subclass>

<!--next Configure our fish-->

<joined-subclass name= "Fish" table= "t_fish_02" >

<!--the key here automatically maps to the primary key of the class above--

<key column= "id" ></key>

<!--is configured with other columns--

<property name= "Fishcoatcount" ></property>

</joined-subclass>

</class>

4 The parent class does not correspond to the table, and the subclasses correspond

Why not use the first one? Because the first kind to write a lot of configuration files is not good to make ...

<!--abstract= "true": This indicates that it is not supposed to be a table--

<class name= "Animal" abstract= "true" >

<!--configuration is the primary key---in the table

<id name= "id" type= "string" >

<generator class= "Assigned" >

</generator>

</id>

<!--is configured for normal columns--

<property name= "Color" ></property>

<property name= "Name" ></property>

<!--The next step is configuring the Add-on table--

<union-subclass name= "Dog" table= "t_dog_03" >

<property name= "num" ></property>

</union-subclass>

<!--the fish is configured below--

<union-subclass name= "Fish" table= "t_fish_03" >

<property name= "Fishcoatcount" ></property>

</union-subclass>

</class>

6 One-to-one mapping

Requirements: Questions about people and identity cards

One person only has one I.D.

An identity card is not just a match for a person

Person-----> ID

Identity card------> personal Relationship

Configuration of the ID card

<class name= "Idcard" table= "T_idcard" >

<!--configuration is the primary key---in the table

<id name= "CardId" type= "Java.lang.Integer" >

<generator class= "Native" >

</generator>

</id>

<!--is configured for normal columns--

<property name= "Cardnum" ></property>

<!--The following is configured for this side of the reference primary key--

<many-to-one name= "People" column= "p_id" class= "People" cascade= "all" ></many-to-one>

</class>

Configuration of the People

<class name= "People" table= "T_people" >

<!--configuration is the primary key---in the table

<id name= "PId" type= "Java.lang.Integer" >

<generator class= "Native" >

</generator>

</id>

<!--is configured for normal columns--

<property name= "Name" ></property>

<!--Next you should configure one-to-one mapping--

<one-to-one name= "Idcard" class= "Idcard" cascade= "All" ></one-to-one>

</class>

Take the first primary key as the second primary key

The mapping relationship of hibernate