利用Kotlin + Spring Boot实现后端开发
这篇文章主要给大家介绍了关于利用Kotlin + Spring Boot实现后端开发的相关资料，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧前言
spring官方最近宣布，将在spring framework 5.0版本中正式支持kotlin语言。这意味着spring boot 2.x版本将为kotlin提供一流的支持。
这并不会令人意外，因为pivotal团队以广泛接纳jvm语言（如scala和groovy）而闻名。
kotlin 是一个基于 jvm 的编程语言，它的简洁、便利早已不言而喻。kotlin 能够胜任 java 做的所有事。目前，我们公司 c 端 的 android 产品全部采用 kotlin 编写。公司的后端项目也可能会使用 kotlin，所以我给他们做一些 demo 进行演示。
示例一：结合 redis 进行数据存储和查询
1.1 配置 gradle
在build.gradle中添加插件和依赖的库。
plugins {
id 'java'
id 'org.jetbrains.kotlin.jvm' version '1.3.0'
}
ext {
libraries = [
rxjava : "2.2.2",
logback : "1.2.3",
spring_boot : "2.1.0.release",
commons_pool2 : "2.6.0",
fastjson : "1.2.51"
]
}
group 'com.kotlin.tutorial'
version '1.0-snapshot'
sourcecompatibility = 1.8
def libs = rootproject.ext.libraries // 库
repositories {
mavencentral()
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
compile "org.jetbrains.kotlin:kotlin-reflect:1.3.0"
testcompile group: 'junit', name: 'junit', version: '4.12'
implementation "io.reactivex.rxjava2:rxjava:${libs.rxjava}"
implementation "ch.qos.logback:logback-classic:${libs.logback}"
implementation "ch.qos.logback:logback-core:${libs.logback}"
implementation "ch.qos.logback:logback-access:${libs.logback}"
implementation "org.springframework.boot:spring-boot-starter-web:${libs.spring_boot}"
implementation "org.springframework.boot:spring-boot-starter-data-redis:${libs.spring_boot}"
implementation "org.apache.commons:commons-pool2:${libs.commons_pool2}"
implementation "com.alibaba:fastjson:${libs.fastjson}"
}
compilekotlin {
kotlinoptions.jvmtarget = "1.8"
}
compiletestkotlin {
kotlinoptions.jvmtarget = "1.8"
}
1.2 创建 springkotlinapplication：
import org.springframework.boot.springapplication
import org.springframework.boot.autoconfigure.springbootapplication
/**
* created by tony on 2018/11/13.
*/
@springbootapplication
open class springkotlinapplication
fun main(args: array<string>) {
springapplication.run(springkotlinapplication::class.java, *args)
}
需要注意open的使用，如果不加open会报如下的错误：
org.springframework.beans.factory.parsing.beandefinitionparsingexception: configuration problem: @configuration class 'springkotlinapplication' may not be final. remove the final modifier to continue.
因为 kotlin 的类默认是final的，所以这里需要使用open关键字。
1.3 配置 redis
在 application.yml 中添加 redis 的配置
spring:
redis:
#数据库索引
database: 0
host: 127.0.0.1
port: 6379
password:
lettuce:
pool:
#最大连接数
max-active: 8
#最大阻塞等待时间(负数表示没限制)
max-wait: -1
#最大空闲
max-idle: 8
#最小空闲
min-idle: 0
#连接超时时间
timeout: 10000
接下来定义 redis 的序列化器，本文采用fastjson，当然使用gson、jackson等都可以，看个人喜好。
import com.alibaba.fastjson.json
import com.alibaba.fastjson.serializer.serializerfeature
import org.springframework.data.redis.serializer.redisserializer
import org.springframework.data.redis.serializer.serializationexception
import java.nio.charset.charset
/**
* created by tony on 2018/11/13.
*/
class fastjsonredisserializer<t>(private val clazz: class<t>) : redisserializer<t> {
@throws(serializationexception::class)
override fun serialize(t: t?) = if (null == t) {
bytearray(0)
} else json.tojsonstring(t, serializerfeature.writeclassname).tobytearray(default_charset)
@throws(serializationexception::class)
override fun deserialize(bytes: bytearray?): t? {
if (null == bytes || bytes.size <= 0) {
return null
}
val str = string(bytes, default_charset)
return json.parseobject(str, clazz) as t
}
companion object {
private val default_charset = charset.forname("utf-8")
}
}
创建 redisconfig
import org.springframework.data.redis.core.redistemplate
import org.springframework.data.redis.connection.redisconnectionfactory
import org.springframework.context.annotation.bean
import org.springframework.data.redis.cache.rediscachemanager
import org.springframework.cache.cachemanager
import org.springframework.cache.annotation.cachingconfigurersupport
import org.springframework.cache.annotation.enablecaching
import org.springframework.context.annotation.configuration
import org.springframework.data.redis.serializer.stringredisserializer
import org.springframework.boot.autoconfigure.condition.conditionalonmissingbean
import org.springframework.boot.context.properties.enableconfigurationproperties
import org.springframework.data.redis.core.redisoperations
import org.springframework.boot.autoconfigure.condition.conditionalonclass
import org.springframework.boot.autoconfigure.data.redis.redisproperties
/**
* created by tony on 2018/11/13.
*/
@enablecaching
@configuration
@conditionalonclass(redisoperations::class)
@enableconfigurationproperties(redisproperties::class)
open class redisconfig : cachingconfigurersupport() {
@bean(name = arrayof("redistemplate"))
@conditionalonmissingbean(name = arrayof("redistemplate"))
open fun redistemplate(redisconnectionfactory: redisconnectionfactory): redistemplate<any, any> {
val template = redistemplate<any, any>()
val fastjsonredisserializer = fastjsonredisserializer(any::class.java)
template.valueserializer = fastjsonredisserializer
template.hashvalueserializer = fastjsonredisserializer
template.keyserializer = stringredisserializer()
template.hashkeyserializer = stringredisserializer()
template.connectionfactory = redisconnectionfactory
return template
}
//缓存管理器
@bean
open fun cachemanager(redisconnectionfactory: redisconnectionfactory): cachemanager {
val builder = rediscachemanager
.rediscachemanagerbuilder
.fromconnectionfactory(redisconnectionfactory)
return builder.build()
}
}
这里也都需要使用open，理由同上。
1.4 创建 service
创建一个 user 对象，使用 datat class 类型。
data class user(var username:string,var password:string):serializable
创建操作 user 的service接口
import com.kotlin.tutorial.user.user
/**
* created by tony on 2018/11/13.
*/
interface iuserservice {
fun getuser(username: string): user
fun createuser(username: string,password: string)
}
创建 service 的实现类：
import com.kotlin.tutorial.user.user
import com.kotlin.tutorial.user.service.iuserservice
import org.springframework.beans.factory.annotation.autowired
import org.springframework.data.redis.core.redistemplate
import org.springframework.stereotype.service
/**
* created by tony on 2018/11/13.
*/
@service
class userserviceimpl : iuserservice {
@autowired
lateinit var redistemplate: redistemplate<any, any>
override fun getuser(username: string): user {
var user = redistemplate.opsforvalue().get("user_${username}")
if (user == null) {
user = user("default","000000")
}
return user as user
}
override fun createuser(username: string, password: string) {
redistemplate.opsforvalue().set("user_${username}", user(username, password))
}
}
1.5 创建 controller
创建一个 usercontroller，包含 createuser、getuser 两个接口。
import com.kotlin.tutorial.user.user
import com.kotlin.tutorial.user.service.iuserservice
import com.kotlin.tutorial.web.dto.httpresponse
import org.springframework.beans.factory.annotation.autowired
import org.springframework.web.bind.annotation.getmapping
import org.springframework.web.bind.annotation.requestmapping
import org.springframework.web.bind.annotation.requestparam
import org.springframework.web.bind.annotation.restcontroller
/**
* created by tony on 2018/11/13.
*/
@restcontroller
@requestmapping("/user")
class usercontroller {
@autowired
lateinit var userservice: iuserservice
@getmapping("/getuser")
fun getuser(@requestparam("name") username: string): httpresponse<user> {
return httpresponse(userservice.getuser(username))
}
@getmapping("/createuser")
fun createuser(@requestparam("name") username: string,@requestparam("password") password: string): httpresponse<string> {
userservice.createuser(username,password)
return httpresponse("create ${username} success")
}
}
创建完 controller 之后，可以进行测试了。
创建用户tony：
查询用户tony：
创建用户monica：
查询用户monica：
示例二：结合 rxjava 模拟顺序、并发地执行任务
2.1 创建 mocktask
首先定义一个任务接口，所有的任务都需要实现该接口：
/**
* created by tony on 2018/11/13.
*/
interface itask {
fun execute()
}
再创建一个模拟的任务，其中delayinseconds用来模拟任务所花费的时间，单位是秒。
import java.util.concurrent.timeunit
import com.kotlin.tutorial.task.itask
/**
* created by tony on 2018/11/13.
*/
class mocktask(private val delayinseconds: int) : itask {
/**
* stores information if task was started.
*/
var started: boolean = false
/**
* stores information if task was successfully finished.
*/
var finishedsuccessfully: boolean = false
/**
* stores information if the task was interrupted.
* it can happen if the thread that is running this task was killed.
*/
var interrupted: boolean = false
/**
* stores the thread identifier in which the task was executed.
*/
var threadid: long = 0
override fun execute() {
try {
this.threadid = thread.currentthread().id
this.started = true
timeunit.seconds.sleep(delayinseconds.tolong())
this.finishedsuccessfully = true
} catch (e: interruptedexception) {
this.interrupted = true
}
}
}
2.2 创建 concurrenttasksexecutor
顺序执行的话比较简单，一个任务接着一个任务地完成即可，是单线程的操作。
对于并发而言，在这里借助 rxjava 的 merge 操作符来将多个任务进行合并。还用到了 rxjava 的任务调度器 scheduler，createscheduler()是按照所需的线程数来创建scheduler的。
import com.kotlin.tutorial.task.itask
import io.reactivex.completable
import io.reactivex.schedulers.schedulers
import org.slf4j.loggerfactory
import org.springframework.util.collectionutils
import java.util.*
import java.util.concurrent.executors
import java.util.stream.collectors
/**
* created by tony on 2018/11/13.
*/
class concurrenttasksexecutor(private val numberofconcurrentthreads: int, private val tasks: collection<itask>?) : itask {
val log = loggerfactory.getlogger(this.javaclass)
constructor(numberofconcurrentthreads: int, vararg tasks: itask) : this(numberofconcurrentthreads, if (tasks == null) null else arrays.aslist<itask>(*tasks)) {}
init {
if (numberofconcurrentthreads < 0) {
throw runtimeexception("amount of threads must be higher than zero.")
}
}
/**
* converts collection of tasks (except null tasks) to collection of completable actions.
* each action will be executed in thread according to the scheduler created with [.createscheduler] method.
*
* @return list of completable actions
*/
private val asconcurrenttasks: list<completable>
get() {
if (tasks!=null) {
val scheduler = createscheduler()
return tasks.stream()
.filter { task -> task != null }
.map { task ->
completable
.fromaction {
task.execute()
}
.subscribeon(scheduler)
}
.collect(collectors.tolist())
} else {
return arraylist<completable>()
}
}
/**
* checks whether tasks collection is empty.
*
* @return true if tasks collection is null or empty, false otherwise
*/
private val istaskscollectionempty: boolean
get() = collectionutils.isempty(tasks)
/**
* executes all tasks concurrent way only if collection of tasks is not empty.
* method completes when all of the tasks complete (or one of them fails).
* if one of the tasks failed the the exception will be rethrown so that it can be handled by mechanism that calls this method.
*/
override fun execute() {
if (istaskscollectionempty) {
log.warn("there are no tasks to be executed.")
return
}
log.debug("executing #{} tasks concurrent way.", tasks?.size)
completable.merge(asconcurrenttasks).blockingawait()
}
/**
* creates a scheduler that will be used for executing tasks concurrent way.
* scheduler will use number of threads defined in [.numberofconcurrentthreads]
*
* @return scheduler
*/
private fun createscheduler() = schedulers.from(executors.newfixedthreadpool(numberofconcurrentthreads))
}
2.3 创建 controller
创建一个 taskscontroller，包含 sequential、concurrent 两个接口，会分别把sequential 和 concurrent 执行任务的时间展示出来。
import com.kotlin.tutorial.task.impl.concurrenttasksexecutor
import com.kotlin.tutorial.task.impl.mocktask
import com.kotlin.tutorial.web.dto.taskresponse
import com.kotlin.tutorial.web.dto.errorresponse
import com.kotlin.tutorial.web.dto.httpresponse
import org.springframework.http.httpstatus
import org.springframework.util.stopwatch
import org.springframework.web.bind.annotation.*
import java.util.stream.collectors
import java.util.stream.intstream
/**
* created by tony on 2018/11/13.
*/
@restcontroller
@requestmapping("/tasks")
class taskscontroller {
@getmapping("/sequential")
fun sequential(@requestparam("task") taskdelaysinseconds: intarray): httpresponse<taskresponse> {
val watch = stopwatch()
watch.start()
intstream.of(*taskdelaysinseconds)
.maptoobj{
mocktask(it)
}
.foreach{
it.execute()
}
watch.stop()
return httpresponse(taskresponse(watch.totaltimeseconds))
}
@getmapping("/concurrent")
fun concurrent(@requestparam("task") taskdelaysinseconds: intarray, @requestparam("threads",required = false,defaultvalue = "1") numberofconcurrentthreads: int): httpresponse<taskresponse> {
val watch = stopwatch()
watch.start()
val delayedtasks = intstream.of(*taskdelaysinseconds)
.maptoobj{
mocktask(it)
}
.collect(collectors.tolist())
concurrenttasksexecutor(numberofconcurrentthreads, delayedtasks).execute()
watch.stop()
return httpresponse(taskresponse(watch.totaltimeseconds))
}
@exceptionhandler(illegalargumentexception::class)
@responsestatus(httpstatus.bad_request)
fun handleexception(e: illegalargumentexception) = errorresponse(e.message)
}
顺序地执行多个任务：http://localhost:8080/tasks/sequential?task=1&task=2&task=3&task=4
每个任务所花费的时间分别是1秒、2秒、3秒和4秒。最后，一共花费了10.009秒。
两个线程并发地执行多个任务：http://localhost:8080/tasks/concurrent?task=1&task=2&task=3&task=4&threads=2
三个线程并发地执行多个任务：http://localhost:8080/tasks/concurrent?task=1&task=2&task=3&task=4&threads=3
总结
本文使用了 kotlin 的特性跟 spring boot 整合进行后端开发。kotlin 的很多语法糖使得开发变得更加便利，当然 kotlin 也是 java 的必要补充。
本文 demo 的 github 地址：https://github.com/fengzhizi715/kotlin-spring-demo
好了，以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对CodeAE代码之家的支持。
原文链接：https://juejin.im/post/5bebb4436fb9a04a072feb74
http://www.zzvips.com/article/170662.html
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