Grails one-to-one Association

One-to-one association is not widely used in development, but I think it is necessary to master the following. One-to-one association has a table with a foreign key, the referenced primary key is generally the primary key of the primary table. Grails also provides good support for one-to-one associations, and the configuration is extremely simple. Grails configuration can have the following three options:

class Face {    Nose nose}class Nose {}

This is a one-way Association, and the following is a two-way Association, but it cannot be updated in cascade mode.

class Face {    Nose nose}class Nose {Face face}

Next, I think this is easy to use, and it can be stored and updated in the level of warranty.

class Face {    Nose nose}class Nose {static belongsTo = [face:Face]}

If one-way Association is used and the level-level joint guarantee and update are used, we recommend that you use the following

class Face {    Nose nose}class Nose {static belongsTo = Face}

The following is my example. I am using the third type. In this case, bidirectional association can also be used for level-based joint guarantee and update.

1. Create a domain object

class PersonInfo {    Integer id;    String name;    CardInfo card;    static mapping = {        table 'm_person'        card column: 'cardId'    }}

class CardInfo {     Integer id;     String birthday;     static belongsTo = [person:PersonInfo]    static mapping = {        table 'm_card'    }}

Person is the master table, and card is the slave table, which is somewhat different from hibernate.

2. Use the Controller to cascade the storage of person and card

@ Transactional def savePersonAndCard () {def p = new PersonInfo () p. setName ("caiyil") def c = new CardInfo () c. setBirthday ("2008-01-03") p. setCard (c) p. save () render "data saved successfully "}

I have also written a method to obtain the birthday of a person.

// Query birthday def queryPersonBirthday () {def personId = params. id def p = PersonInfo. get (personId) render p. getCard (). getBirthday ()} through person ()}

Grails supports many-to-many operations, but remember that many-to-many operations require one party to maintain the association. For details, refer to grails development documentation.