java - JPA Join Column -

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i have 3 tables in database.

first one(categories) includes: id, category, isactive

second one(menu) includes: parentid , childid.

third one(items) includes: id, name , price.

first table has relationship second. want relationship between second , third now.

second table has these values in database:

  • 7(id), book1(name), 120(price)
  • 7(id), book2(name), 100(price)
  • 8(id), car1(name), 1620(price)
  • 8(id), car2(name), 520(price)
  • 8(id), car3(name), 5520(price)
  • 9(id), house1(name), 10000(price)
  • 9(id), house2(name), 11000(price)
  • 9(id), house3(name), 15000(price)

at moment have joined column childid column id.

menu.java

@embeddedid menuid id;  @column(name="parentid") private integer parentid;  @column(name="childid") private integer childid;  @onetoone @joincolumn(name="childid",referencedcolumnname="id")  private categories subcategories;  public categories getsubcategories() {     return this.subcategories; }  public void setsubategories(categories subcategories) {     this.subcategories = subcategories;      }  @onetoone @joincolumn(name="parentid", referencedcolumnname="id") private categories categories;  public categories getcategories() {     return this.categories; }  public void setcategories(categories categories) {     this.categories = categories; }  @onetoone @joincolumn(name="childid",referencedcolumnname="id") private items items; public items getitems() {     return this.items; }  public void setitems(items items) {     this.items = items; }

items.java has no modifications subcategories.java

i using json object print out values:

jsonobject.put("parentid", menu.getparentid()); jsonobject.put("childid", menu.getchildid()); jsonobject.put("categories", menu.getcategories().getcategory()); jsonobject.put("subcategories", menu.getsubcategories().getcategory()); jsonobject.put("itemid", menu.getitems().getid()); jsonobject.put("product", menu.getitems().getproduct()); jsonobject.put("brand", menu.getitems().getbrand()); jsonobject.put("sum", menu.getitems().getsum());

it works, works not imagine on project. prints same values:

  • 7(id), book1(name), 120(price)
  • 7(id), book1(name), 120(price)
  • 8(id), car1(name), 1620(price)
  • 8(id), car1(name), 1620(price)
  • 8(id), car1(name), 1620(price)
  • 9(id), house1(name), 10000(price)
  • 9(id), house1(name), 10000(price)
  • 9(id), house1(name), 10000(price)

and on... not this:

  • 7(id), book1(name), 120(price)
  • 7(id), book2(name), 100(price)
  • 8(id), car1(name), 1620(price)
  • 8(id), car2(name), 520(price)
  • 8(id), car3(name), 5520(price)
  • 9(id), house1(name), 10000(price)
  • 9(id), house2(name), 11000(price)
  • 9(id), house3(name), 15000(price)

so question should use @onetomany method? or in wrong way?

using @onetoone extending table (more columns) rows.

it seems trying set relation model orders/bills , positions of orders/bills.

normally (at least so) create "parent"-table orders.

table order: --------------- oder_id | customer | date | ... --------+----------+------+-----     1   |  cust_1  | ...  | ...     2   |  cust_3  | ...  | ...

the positions of order in "child"-table order_positions. foreign key constraint (order_position.order_id order.order_id) ensures data integrity.

table order_position: -----------------------  id | oder_id | item     | price | ... ----+---------+----------+-------+-----   1 |     1   |  book_1  | 100   | ...   2 |     1   |  book_2  | 200   | ...   3 |     2   |  car_1   | 2500  | ...   4 |     2   |  car_2   | 234   | ...

to anser question: yes, in jpa should use @onetomanyin oder-entity , (if want bidirectional relationship) manytoonein orderpostion-entity. take @ examples in objectdb-wiki


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