Spring Boot和Kotlin的無縫整合與完美交融

2024-07-14 08:41:13

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前言

本文講解 Spring Boot2 基礎下，如何使用 Kotlin，并無縫整合與完美交融。為了讓讀者更加熟悉 Kotlin 的語法糖，筆者會在未來的幾篇文章中，聊聊 Kotlin 的新特性及其語法糖。下面話不多說了，來一起看看詳細的介紹吧

環境依賴

修改 POM 文件，添加 spring boot 依賴。

<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.2.RELEASE</version> <relativePath/></parent><dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jdbc</artifactId> </dependency></dependencies>

緊接著，我們需要添加 mysql 依賴。

<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.35</version></dependency><dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.0.14</version></dependency>

最后，添加 Kotlin 依賴。

<dependency> <groupId>org.jetbrains.kotlin</groupId> <artifactId>kotlin-stdlib-jdk8</artifactId></dependency><dependency> <groupId>org.jetbrains.kotlin</groupId> <artifactId>kotlin-reflect</artifactId></dependency><dependency> <groupId>org.jetbrains.kotlin</groupId> <artifactId>kotlin-stdlib</artifactId></dependency>

注意的是，在 Kotlin 中，data class 默認沒有無參構造方法，并且 data class 默認為 final 類型，不可以被繼承。注意的是，如果我們使用 Spring + Kotlin 的模式，那么使用 @autowared 就可能遇到這個問題。因此，我們可以添加 NoArg 為標注的類生成無參構造方法。使用 AllOpen 為被標注的類去掉 final，允許被繼承。

<plugin> <artifactId>kotlin-maven-plugin</artifactId> <groupId>org.jetbrains.kotlin</groupId> <version>${kotlin.version}</version> <executions> <execution> <id>compile</id> <goals> <goal>compile</goal> </goals> </execution> <execution> <id>test-compile</id> <goals> <goal>test-compile</goal> </goals> </execution> </executions> <dependencies> <dependency> <groupId>org.jetbrains.kotlin</groupId> <artifactId>kotlin-maven-noarg</artifactId> <version>${kotlin.version}</version> </dependency> <dependency> <groupId>org.jetbrains.kotlin</groupId> <artifactId>kotlin-maven-allopen</artifactId> <version>${kotlin.version}</version> </dependency> </dependencies></plugin>

至此，我們 Maven 的依賴環境大致配置完畢。完整的源碼，可以參見文末 GitHub 倉庫。

數據源

方案一使用 Spring Boot 默認配置

使用 Spring Boot 默認配置，不需要在創建 dataSource 和 jdbcTemplate 的 Bean。

在 src/main/resources/application.properties 中配置數據源信息。

spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.url=jdbc:mysql://localhost:3307/springboot_dbspring.datasource.username=rootspring.datasource.password=root

方案二手動創建

在 src/main/resources/config/source.properties 中配置數據源信息。

# mysqlsource.driverClassName = com.mysql.jdbc.Driversource.url = jdbc:mysql://localhost:3306/springboot_dbsource.username = rootsource.password = root

這里，創建 dataSource 和jdbcTemplate。

@Configuration@EnableTransactionManagement@PropertySource(value = *arrayOf("classpath:config/source.properties"))open class BeanConfig {  @Autowired private lateinit var env: Environment  @Bean open fun dataSource(): DataSource { val dataSource = DruidDataSource() dataSource.driverClassName = env!!.getProperty("source.driverClassName").trim() dataSource.url = env.getProperty("source.url").trim() dataSource.username = env.getProperty("source.username").trim() dataSource.password = env.getProperty("source.password").trim() return dataSource }  @Bean open fun jdbcTemplate(): JdbcTemplate { val jdbcTemplate = JdbcTemplate() jdbcTemplate.dataSource = dataSource() return jdbcTemplate }}

腳本初始化

先初始化需要用到的 SQL 腳本。

CREATE DATABASE /*!32312 IF NOT EXISTS*/`springboot_db` /*!40100 DEFAULT CHARACTER SET utf8 */; USE `springboot_db`; DROP TABLE IF EXISTS `t_author`; CREATE TABLE `t_author` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT '用戶ID', `real_name` varchar(32) NOT NULL COMMENT '用戶名稱', `nick_name` varchar(32) NOT NULL COMMENT '用戶匿名', PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

使用 JdbcTemplate 操作

實體對象

class Author { var id: Long? = null var realName: String? = null var nickName: String? = null}

DAO相關

interface AuthorDao { fun add(author: Author): Int fun update(author: Author): Int fun delete(id: Long): Int fun findAuthor(id: Long): Author? fun findAuthorList(): List<Author>}

我們來定義實現類，通過 JdbcTemplate 定義的數據訪問操作。

@Repositoryopen class AuthorDaoImpl : AuthorDao {  @Autowired private lateinit var jdbcTemplate: JdbcTemplate  override fun add(author: Author): Int { return jdbcTemplate.update("insert into t_author(real_name, nick_name) values(?, ?)", author.realName, author.nickName) }  override fun update(author: Author): Int { return jdbcTemplate.update("update t_author set real_name = ?, nick_name = ? where id = ?", *arrayOf(author.realName, author.nickName, author.id)) }  override fun delete(id: Long): Int { return jdbcTemplate.update("delete from t_author where id = ?", id) }  override fun findAuthor(id: Long): Author? { val list = jdbcTemplate.query<Author>("select * from t_author where id = ?", arrayOf<Any>(id), BeanPropertyRowMapper(Author::class.java)) return list?.get(0); }  override fun findAuthorList(): List<Author> { return jdbcTemplate.query("select * from t_author", arrayOf(), BeanPropertyRowMapper(Author::class.java)) }}

Service相關

interface AuthorService { fun add(author: Author): Int fun update(author: Author): Int fun delete(id: Long): Int fun findAuthor(id: Long): Author? fun findAuthorList(): List<Author>}

我們來定義實現類，Service 層調用 Dao 層的方法，這個是典型的套路。

@Service("authorService")open class AuthorServiceImpl : AuthorService {  @Autowired private lateinit var authorDao: AuthorDao  override fun update(author: Author): Int { return this.authorDao.update(author) }  override fun add(author: Author): Int { return this.authorDao.add(author) }  override fun delete(id: Long): Int { return this.authorDao.delete(id) }  override fun findAuthor(id: Long): Author? { return this.authorDao.findAuthor(id) }  override fun findAuthorList(): List<Author> { return this.authorDao.findAuthorList() }}

Controller相關

為了展現效果，我們先定義一組簡單的 RESTful API 接口進行測試。

@RestController@RequestMapping(value = "/authors")class AuthorController {  @Autowired private lateinit var authorService: AuthorService  /** * 查詢用戶列表 */ @RequestMapping(method = [RequestMethod.GET]) fun getAuthorList(request: HttpServletRequest): Map<String, Any> { val authorList = this.authorService.findAuthorList() val param = HashMap<String, Any>() param["total"] = authorList.size param["rows"] = authorList return param }  /** * 查詢用戶信息 */ @RequestMapping(value = "/{userId://d+}", method = [RequestMethod.GET]) fun getAuthor(@PathVariable userId: Long, request: HttpServletRequest): Author { return authorService.findAuthor(userId) ?: throw RuntimeException("查詢錯誤") }  /** * 新增方法 */ @RequestMapping(method = [RequestMethod.POST]) fun add(@RequestBody jsonObject: JSONObject) { val userId = jsonObject.getString("user_id") val realName = jsonObject.getString("real_name") val nickName = jsonObject.getString("nick_name")  val author = Author() author.id = java.lang.Long.valueOf(userId) author.realName = realName author.nickName = nickName try { this.authorService.add(author) } catch (e: Exception) { throw RuntimeException("新增錯誤") } }  /** * 更新方法 */ @RequestMapping(value = "/{userId://d+}", method = [RequestMethod.PUT]) fun update(@PathVariable userId: Long, @RequestBody jsonObject: JSONObject) { var author = this.authorService.findAuthor(userId) val realName = jsonObject.getString("real_name") val nickName = jsonObject.getString("nick_name") try { if (author != null) { author.realName = realName author.nickName = nickName this.authorService.update(author) } } catch (e: Exception) { throw RuntimeException("更新錯誤") }  }  /** * 刪除方法 */ @RequestMapping(value = "/{userId://d+}", method = [RequestMethod.DELETE]) fun delete(@PathVariable userId: Long) { try { this.authorService.delete(userId) } catch (e: Exception) { throw RuntimeException("刪除錯誤") } }}

最后，我們通過 SpringKotlinApplication 運行程序。

@SpringBootApplication(scanBasePackages = ["com.lianggzone.demo.kotlin"])open class SpringKotlinApplication{ fun main(args: Array<String>) { SpringApplication.run(SpringKotlinApplication::class.java, *args) }}

關于測試

這里，筆者推薦 IDEA 的 Editor REST Client。IDEA 的 Editor REST Client 在 IntelliJ IDEA 2017.3 版本就開始支持，在 2018.1 版本添加了很多的特性。事實上，它是 IntelliJ IDEA 的 HTTP Client 插件。參見筆者之前的另一篇文章：快速測試 API 接口的新技能

### 查詢用戶列表GET http://localhost:8080/authorsAccept : application/jsonContent-Type : application/json;charset=UTF-8 ### 查詢用戶信息GET http://localhost:8080/authors/15Accept : application/jsonContent-Type : application/json;charset=UTF-8 ### 新增方法POST http://localhost:8080/authorsContent-Type: application/json { "user_id": "21", "real_name": "梁桂釗", "nick_name": "梁桂釗"} ### 更新方法PUT http://localhost:8080/authors/21Content-Type: application/json { "real_name" : "lianggzone", "nick_name": "lianggzone"} ### 刪除方法DELETE http://localhost:8080/authors/21Accept : application/jsonContent-Type : application/json;charset=UTF-8