SpringBoot 与 Kotlin 完美交融

时间 2019-11-30

原文原文链接

原文地址：梁桂钊的博客java

博客地址：blog.720ui.commysql

欢迎转载，转载请注明做者及出处，谢谢！git

本文讲解 Spring Boot2 基础下，如何使用 Kotlin，并没有缝整合与完美交融。为了让读者更加熟悉 Kotlin 的语法糖，笔者会在将来的几篇文章中，聊聊 Kotlin 的新特性及其语法糖。github

环境依赖

修改 POM 文件，添加 spring boot 依赖。web

<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>
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紧接着，咱们须要添加 mysql 依赖。spring

<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>
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最后，添加 Kotlin 依赖。sql

<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>
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注意的是，在 Kotlin 中，data class 默认没有无参构造方法，而且 data class 默认为 final 类型，不能够被继承。注意的是，若是咱们使用 Spring + Kotlin 的模式，那么使用 @autowared 就可能遇到这个问题。所以，咱们能够添加 NoArg 为标注的类生成无参构造方法。使用 AllOpen 为被标注的类去掉 final，容许被继承。json

<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>
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至此，咱们 Maven 的依赖环境大体配置完毕。完整的源码，能够参见文末 GitHub 仓库。springboot

数据源

方案一使用 Spring Boot 默认配置

使用 Spring Boot 默认配置，不须要在建立 dataSource 和 jdbcTemplate 的 Bean。bash

在 src/main/resources/application.properties 中配置数据源信息。

spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3307/springboot_db
spring.datasource.username=root
spring.datasource.password=root

方案二手动建立

在 src/main/resources/config/source.properties 中配置数据源信息。

# mysql
source.driverClassName = com.mysql.jdbc.Driver
source.url = jdbc:mysql://localhost:3306/springboot_db
source.username = root
source.password = root
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这里，建立 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
    }
}
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脚本初始化

先初始化须要用到的 SQL 脚本。

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 '用户ID',
  `real_name` varchar(32) NOT NULL COMMENT '用户名称',
  `nick_name` varchar(32) NOT NULL COMMENT '用户匿名',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
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使用 JdbcTemplate 操做

实体对象

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

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>
}
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咱们来定义实现类，经过 JdbcTemplate 定义的数据访问操做。

@Repository
open 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))
    }
}
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Service相关

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>
}
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咱们来定义实现类，Service 层调用 Dao 层的方法，这个是典型的套路。

@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()
    }
}
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Controller相关

为了展示效果，咱们先定义一组简单的 RESTful API 接口进行测试。

@RestController
@RequestMapping(value = "/authors")
class AuthorController {

    @Autowired
    private lateinit var authorService: AuthorService

    /**
     * 查询用户列表
     */
    @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
    }

    /**
     * 查询用户信息
     */
    @RequestMapping(value = "/{userId:\\d+}", method = [RequestMethod.GET])
    fun getAuthor(@PathVariable userId: Long, request: HttpServletRequest): Author {
        return authorService.findAuthor(userId) ?: throw RuntimeException("查询错误")
    }

    /**
     * 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("新增错误")
        }
    }

    /**
     * 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("更新错误")
        }

    }

    /**
     * 删除方法
     */
    @RequestMapping(value = "/{userId:\\d+}", method = [RequestMethod.DELETE])
    fun delete(@PathVariable userId: Long) {
        try {
            this.authorService.delete(userId)
        } catch (e: Exception) {
            throw RuntimeException("删除错误")
        }
    }
}
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最后，咱们经过 SpringKotlinApplication 运行程序。

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

这里，笔者推荐 IDEA 的 Editor REST Client。IDEA 的 Editor REST Client 在 IntelliJ IDEA 2017.3 版本就开始支持，在 2018.1 版本添加了不少的特性。事实上，它是 IntelliJ IDEA 的 HTTP Client 插件。参见笔者以前的另外一篇文章：快速测试 API 接口的新技能 | 梁桂钊的博客

### 查询用户列表
GET http://localhost:8080/authors
Accept : application/json
Content-Type : application/json;charset=UTF-8

### 查询用户信息
GET http://localhost:8080/authors/15
Accept : application/json
Content-Type : application/json;charset=UTF-8

### 新增方法
POST http://localhost:8080/authors
Content-Type: application/json

{
    "user_id": "21",
    "real_name": "梁桂钊",
    "nick_name": "梁桂钊"
}

### 更新方法
PUT http://localhost:8080/authors/21
Content-Type: application/json

{
    "real_name" : "lianggzone",
    "nick_name": "lianggzone"
}


### 删除方法
DELETE http://localhost:8080/authors/21
Accept : application/json
Content-Type : application/json;charset=UTF-8
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总结

经过，上面这个简单的案例，咱们发现 Spring Boot 整合 Kotlin 很是容易，并简化 Spring 应用的初始搭建以及开发过程。为了让读者更加熟悉 Kotlin 的语法糖，笔者会在将来的几篇文章中，聊聊 Kotlin 的新特性及其语法糖。

源代码

相关示例完整代码： spring-kotlin-samples

（完，转载请注明做者及出处。）

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