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[Kotlin] DAO & Zygarde

What is Dao ?​

DAO (Data Access Object Pattern) pattern is used to separate low level data accessing API or operations from high level business services. Following are the participants in Data Access Object Pattern.

  • Data Access Object Interface - This interface defines the standard operations to be performed on a model object(s).

  • Data Access Object concrete class - This class implements above interface. This class is responsible to get data from a data source which can be database / xml or any other storage mechanism.

  • Model Object or Value Object - This object is simple POJO containing get/set methods to store data retrieved using DAO class. Ex: Entity is a kind of Value Object.

info

If you want to know more detail about the relation between DAO and Entity, please read this example

What is Zygarde ?​

Zygarde is an open soure. One of modules called zygarde-jpa-codegen can automatically generating DAO based on JPA

Usage​

step 1: Install​

repositories {
  maven("https://nexus.puni.tw/repository/maven-releases/")
}

dependencies {
  implementation("zygarde:zygarde-jpa:$zygardeVersion")
  kapt("zygarde:zygarde-jpa-codegen:$zygardeVersion")
}

step 2: create your entity​

import jakarta.persistence.*
import zygarde.codegen.ZyModel
import java.io.Serializable

@Table(schema = "public", name = "roles")
@ZyModel
@Entity
class Role(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Int? = null,

    @Column(nullable = false)
    val name: String,

    val description: String? = null,

    val available: Boolean? = null,

    @Column(name = "project_id")
    val projectId: Int? = null
) : Serializable

step 3: run command for generating DAO​

./gradlew kaptKotlin

step 4: then you will see DAO​

import kotlin.Int
import will.com.demo.entity.Role
import zygarde.`data`.jpa.dao.ZygardeEnhancedDao

public interface RoleDao : ZygardeEnhancedDao<Role, Int>

and use it like:

@RestController
@RequestMapping
class TestController(
    private val roleDao: RoleDao
) {
    @GetMapping("/data")
    fun getData(): String {
        val data = roleDao.searchOne { name() eq "root" }
        return data?.description ?: "empty"
    }

}

Here is a minimal demo for spring boot v3 and zygarde v3. If you want to use it and then meet some problem, you can leave your question on issues.

Reference​