簡介

我們都知道java是面向物件的編程語言，但是其實撰寫代碼有些復雜性，即使后來出現了jdk8加大代碼開發的便捷性，但是依然不夠簡潔，就算強大的jvm作為運行環境，也難以各大環境中互相運行，google提倡出kotlin語言開發，同時植入了Android內部，無需插件即可開發，這里不做過多的簡介語言的優缺點，每種語言都有自己的不足和有點，主要針對專案情況而進行，但是其實個人還是建議用java，畢竟java比較普遍和目前學習資料也比較多！接下來我們居于gradle構建kotlin的RestFul工程，

示例

簡介技術體系

1. 本應用編輯工具是idea，因為新版本的idea版本工具具有kotlin插件
2. 資料庫是居于docker的mysql服務
3. 基礎環境是jdk8
4. spring boot作為技術框架

操作流程

搭建mysql&jdk

Mysql搭建
docker的mysql啟動檔案docker-compose.yaml：

version: '2'

services:
  mysql:
    image: mysql:5.7
    command: [mysqld, --character-set-server=utf8mb4, --collation-server=utf8mb4_unicode_ci]
    environment:
      MYSQL_ROOT_PASSWORD: root
      TZ: Asia/Shanghai
    ports:
      - "3307:3306"
    volumes: 
      - "~/data/mysql:/var/lib/mysql"

新建上面檔案（touch docker-compose.yaml）,當前目錄啟動mysql服務，docker-compose up -d
jdk配置
JAVA_HOME=你的jdk的home目錄
PATH= J A V A H O M E / b i n : JAVA_HOME/bin: JAVAH?OME/bin:PATH:.
CLASSPATH= J A V A H O M E / l i b / t o o l s . j a r : JAVA_HOME/lib/tools.jar: JAVAH?OME/lib/tools.jar:JAVA_HOME/lib/dt.jar:.
export JAVA_HOME
export CLASSPATH

初始化spring boot

這里采用官網初始化方式鏈接，如下圖：

gradler包加載如下：

	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
	implementation("org.springframework.boot:spring-boot-starter-web")
	implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
	implementation("org.jetbrains.kotlin:kotlin-reflect")
	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
	implementation("org.hibernate.javax.persistence:hibernate-jpa-2.1-api:1.0.2.Final")
	runtimeOnly("mysql:mysql-connector-java")
	testImplementation("org.springframework.boot:spring-boot-starter-test")

專案包結構

application檔案

server:
  port: 8080
spring:
  datasource:
    url: jdbc:mysql://localhost:3307/kotlin
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver
    dbcp2:
      test-while-idle: true
      validation-query: SELECT 1
  jpa:
    database: MYSQL
    show-sql: true
    database-platform: org.hibernate.dialect.MySQL5Dialect
    hibernate:
      naming:
        physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy

啟動類，并添加掃面路徑

檔案資料類

// Config 類
package com.lgh.run.config
import org.springframework.boot.autoconfigure.domain.EntityScan
import org.springframework.context.annotation.ComponentScan
import org.springframework.data.jpa.repository.config.EnableJpaRepositories
@ComponentScan("com.lgh")
@EntityScan("com.lgh.entity")
@EnableJpaRepositories("com.lgh.repository")
class Config

// DemoApplication 類
package com.lgh.run
import com.lgh.run.config.Config
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Import
@SpringBootApplication
@Import(Config::class)
class DemoApplication
fun main(args: Array<String>) {
	runApplication<DemoApplication>(*args)
}

// User
package com.lgh.entity
import javax.persistence.*
@Entity
class User(
        @Id @GeneratedValue(strategy = GenerationType.AUTO) val id:Long?,
        @Column(name = "user_id") val userId:Long?,
        @Column(name = "user_name") val userName:String?
)

// UserRepository
package com.lgh.repository
import com.lgh.entity.User
import org.springframework.data.repository.CrudRepository
interface UserRepository: CrudRepository<User,Long>{
    fun findByUserNameLike(uName:String):Collection<User>?
    fun findByUserId(uId:Long):User?
}

// UserServiceImpl 類
package com.lgh.service
import com.lgh.entity.User
import com.lgh.repository.UserRepository
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Service
@Service
class UserServiceImpl {
    @Autowired
    val userRepository: UserRepository? = null
    fun findByUName(uName: String): Collection<User>? = userRepository?.findByUserNameLike(uName?.plus("%"))
    fun findByUId(id:Long): User? = userRepository?.findByUserId(id)
}

# UserRepository
package com.lgh.repository
import com.lgh.entity.User
import org.springframework.data.repository.CrudRepository
interface UserRepository: CrudRepository<User,Long>{
    fun findByUserNameLike(uName:String):Collection<User>?
    fun findByUserId(uId:Long):User?
}

// UserController
package com.lgh.controller
import com.lgh.entity.User
import com.lgh.service.UserServiceImpl
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.PathVariable
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController
@RestController
@RequestMapping("/users")
class UserController {
    @Autowired
    val userService: UserServiceImpl? = null
    @GetMapping("/id/{id}")
    fun findUserById(@PathVariable("id") id: Long): User? = userService?.findByUId(id)
    @GetMapping("/name/{userName}")
    fun  findByUserName(@PathVariable("userName") userName:String): Collection<User>? = userService?.findByUName(userName)
}

原始碼地址

github

總結&反思

留給觀看者總結反思！