Save Long Associations

What is Long Association

A long association refers to not only changing the association relationship between the current object and other objects, but also further modifying the associated object.

For the UI interface, it is usually manifested as nested parent-child forms (or even recursive trees). The forms are diverse, and sub-forms embedded in forms are quite common, as follows:

Purchaser

Schneewittchen

Purchaser

Province

Province

City

City

Address

Address

Order Items

Commodity	Quantity	Unit price	Item price	Delete
Timeless Vitamin C Plus E 10 Percent Ferulic Acid Serum Serum Unisex 1 oz		14.69	29.38
Olaplex No. 4 Bond Maintenance Shampoo		30	30

Total price:59.379999999999995

info

As long as developers are willing, the depth of this nested parent-child form structure can be more than two layers. In theory, the depth can be infinite, which is why it is called a long association.

Write DTO

In the current example in the entity definition, the more suitable example as a long association to save is the BookStore and its associated books collection.

1. Install DTO language Intellij plugin: https://github.com/ClearPlume/jimmer-dto (This process is not required but highly recommended)

2. Create a new directory src/main/dto

3. Under src/main/dto, create a file BookStore.dto and write the following code:

   BookStore.dto

   export org.doc.j.model.BookStore  
       -> package org.doc.j.model.dto  
   
   input BookStoreWithLongAssociation {
       #allScalars(this) 
       books { // LongAssociation
           #allScalars(this)
           -id
           id(authors) as authorIds 
       }
   }

Generated Code

After compilation, Jimmer will generate the following code:

Java

BookStoreWithLongAssociation.java

@GeneratedBy(
        file = "<yourproject>/src/main/dto/BookStore.dto"  
)
public class BookStoreWithLongAssociation implements Input<BookStore> {

    @Nullable
    private Long id;

    @NotNull
    private String name;   

    @Nullable
    private String website;

    @NotNull
    private List<TargetOf_books> books;  

    ...Omit other methods...

    public static class TargetOf_books implements Input<Book> {  

        @NotNull 
        private String name;

        private int edition;

        @NotNull
        private BigDecimal price;

        @NotNull
        private List<Long> authorIds;

        ...Omit other methods...
    }  
}

Kotlin

BookStoreWithLongAssociation.kt

@GeneratedBy(
        file = "<yourproject>/src/main/dto/BookStore.dto"  
)
data class BookStoreWithLongAssociation(  
    val id: Long?
    val name: String,
    val website: String?,
    val books: List<TargetOf_books>  
) : Input<BookStore> {
    
    ...Omit other methods...  

    data class TargetOf_authors(  
        val name: String,
        val edition: Int, 
        val price: BigDecimal, 
        val authorIds: List<Long>
    )  
}

Write HTTP Service

Java

BookStoreController.java

@RestController  
public class BookStoreController {  

    private final JSqlClient sqlClient;

    public BookController(JSqlClient sqlClient) {
        this.sqlClient = sqlClient; 
    }  

    @PutMapping("/bookStore")
    public int saveBookStoreWithLongAssociation(
        @RequestBody BookStoreWithLongAssociation input
    ) {
        return sqlClient
            .save(input)
            .getTotalAffectedRowCount();
    }
}

Kotlin

BookStoreController.java

class BookStoreController(
    private val sqlClient: KSqlClient   
) {  

    @PutMapping("/bookStore")  
    fun saveBookStoreWithLongAssociation(
        @RequestBody input: BookStoreWithLongAssociation  
    ): Int =
        sqlClient
            .save(input)
            .totalAffectedRowCount
}

It can be seen that no matter how the Input DTO changes, Jimmer still only needs one method call to complete data saving.