Hibernate relationship ing

This article is the original blogger, allowed to reprint, but please declare the original address: www.coselding.cnblog88-140.html 1, ing:. one-to-one: Primary Key Association one-way: foreign key Association two-way: foreign key association or intermediate table joint primary key: @ OneToOne: one-to-one association, annotation on the get method referenced by the peer class @ Join

This article is the original blogger, allowed to reprint, but please declare the original address: http://www.coselding.cn/blog/8/8-140.html 1, ing:. one-to-one: Primary Key Association one-way: foreign key Association two-way: foreign key association or intermediate table joint primary key: @ OneToOne: one-to-one association, annotation on the get method referenced by the peer class @ Join

This article is the original blogger, allowed to reprint, but please declare the original address: http://www.coselding.cn/blog/8/8-140.html

1. Link ing:
A. One-to-one: Primary Key Association
Unidirectional: foreign key Association
Bidirectional: foreign key association or intermediate table
Joint primary key:
@ OneToOne: one-to-one association, which is annotated on the get method referenced by the peer class
@ JoinColumn: sets the associated foreign key name and name attribute.
@ PrimaryKeyJoinColumn: Set primary key Association
@ JoinColumns set the joint primary key
Xml usage Label to add the unique attribute.
B. One-to-multiple: Add a Set of multiple parties
Annotation: @ onetoworkflow and @ JoinColumn specify the foreign key names of multiple parties
Xml:
C. Multiple-to-one: Add Foreign keys to multiple parties
Annotation: @ ManyToOne
Xml:
Note: one-to-many and multiple-to-one bidirectional relationships are handed over to multiple parties for maintenance, and mappedBy is set at @ onetoworkflow.
Attribute, xml in Set inverse = "false"
D. many to many:
Unidirectional:
Note: @ manytoable, @ JoinTable specifies the middle table name and column name on the maintenance set,
JoinColumns, JoinColumn, inverseJoinColumn
Xml:
Bidirectional:
Annotation: Set @ ManyToMany (mappedBy = "") on the other side of the Set Based on One-Way "")
Xml: the other side is also set Tag
E. Component ing: beans that are part of a table are not used as entities, such as student IDs as part of student entities;
Add @ Embedded
Used in Xml Tag
Note: (1) the edby attribute must be set for Bidirectional Association. Property-ref attribute
Indicates that the link is dominated by the other party;
(2) Two-way relationships should pay attention to the possibility of stack overflow of entity infinite loop calls during the call process;
2. add, delete, modify, and query under the association:
(1) cascade operations of association relationship settings only affect addition, deletion, and modification;
(2) If the associated object is one party, the EAGER is retrieved by default;
(3) If the associated object is multiple parties, the default value is delayed loading and LAZY;
(4) fetch: sets query and read cascade operations, which only affects query operations. The default value is LAZY;
(5) two-way Association operations may lead to repeated operations. Pay attention to setting delayed loading to avoid unnecessary operations;
(6) Delete: first query and then delete to prevent cascading deletion-damage the association relationship of memory entities or HQL;
3. Set ing:
(1) conventional method: Set;
(2) List: Add annotation and Set. List is to be able to sort. @ OrderBy specifies the sorting parameter;
(3) Map: The key is a non-repeated child segment (most of which is a primary key), @ MapKey; value is a set element entity, and is more suitable for queries;
4. Inheritance ing:
(1) inheritance relationship of a few attributes: Single-Table. A Table stores all classes and adds a type to mark the seat segment;
(2) Each Class has its own Table: Table-per-Class. It cannot store the inherited polymorphism. It is difficult to inherit the polymorphism, and the uniqueness of each entity's primary key must be maintained;
(3) According to the inheritance relationship, the parent class has tables and sub-classes also have tables, but the common attributes are in the parent table: Joined. The parent and sub-tables must set primary key associations to maintain primary key uniqueness, the query must be connected to the table. The new subclass must create a new table;
Annotation: A. @ Inheritance: Specify the Inheritance ing and specify the Inheritance ing policy for the parent class;
B. @ DiscriminatorColumn: indicates the type flag bits of the class for the parent class;
C. @ DiscriminatorValue ("tag bit value"): class type tag bit value;
5. Tree map:
(1) Object Design: id, Father's Day point reference, child node set, and other node content;
(2) Table Design: id, parent_id, and other node content columns;
(3) set @ Entity, @ Id, primary key generation policy, @ ManyToOne (set the foreign key column "parent_id"), and @ onetoworkflow (mappedBy = "parent ");
(4) set and modify the cascade. Select LAZY or EAGER for specific analysis;
(5) set the parent-child relationship between objects and store them in the database;
(6) recursive queries are used for queries;

This article is the original blogger, allowed to reprint, but please declare the original address: http://www.coselding.cn/blog/8/8-140.html