Jpa how to customize the query one-to-many mapping-CodePudding

If there are so three entities User, the Orders, roles, the relationship between the following
The User and the Orders are a one-to-many relationship between
User and Role is a one-to-many relationship between
The following entity content

 
The class User {
private Long id; 
private String name; 
Private XXX;//other properties no longer list 


The @onetomany (mappedBy="user") 
Private Set The orders; 

The @onetomany (mappedBy="user") 
Private Set Roles; 


} 

The class the Orders {
private Long id; 
Private String order_num; 
Private XXX;//other properties no longer list 

@ ManyToOne 
@ JoinColumn (name="userId") 
private User user; 


} 

The class Roles {
private Long id; 
private String name; 
private String desc; 
Private XXX;//other properties no longer list 

@ ManyToOne 
@ JoinColumn (name="userId") 
private User user; 


}

When I want to custom query certain fields you can use the following SQL (SQL="select id, name from the Users where XXX"), but check out the entity does not contain Set The figures,

so the question comes, how do I custom query a one-to-many relationship of entities, such as: execute the query the User entity id, name, Set These attributes, instead of a cascade query Role this table, mapping and the User entity how to query, namely query results is a List In the User id, name, and collections Set

CodePudding user response:

You can use a JPQL + vo, is roughly such

 
Select new UserOrderVo (u.i d, u.n ame, u.o. rders) from user u.

If need to add a UserOrderVo constructor, parameter type is the structure of the above types

CodePudding user response:

reference 1st floor masteryourself response:

can use a JPQL + vo, is roughly such
 
Select new UserOrderVo (u.i d, u.n ame, u.o. rders) from user u. 
If need to add a UserOrderVo constructor, the structure of the parameter type is above type

If it is a basic fields such as id, name that you want, but u.o. rders this is no good

CodePudding user response:

The select u from User u where XXX;
This will automatically packaging, if the configuration lazy loading, will be set at the time of call to query, if lazy loading to false, the query for the first time will query

CodePudding user response:

The

reference 3 floor yugehha response:

select u from User u where XXX;
This will automatically packaging, if the configuration lazy loading, will be set at the time of call to query, if lazy loading to false, the query for the first time will query out

Because using rest style, even if is configured with lazy loading, when the json serialization, will also go to query, I just don't want to do useless query, this efficiency may be low () when data is large, so I think the custom query, what kind of data, then I can check what data

CodePudding user response:

One-to-many, need to put control in many side, such a query that party won't load more than one party,

CodePudding user response:

The eldest brother have a solution? This problem should be very common, why not one on baidu