java-scala 高效混合开发
java scala 混合开发
知名应用
- Kafka（消息系统）
- Spark （计算引擎）
- Play（新一代web全栈框架）
- Akka (高可伸缩性的 Java 和 Scala 的 Actor 模型应用)
scala优点
Scala 是一种有趣的语言。它一方面吸收继承了多种语言中的优秀特性，一方面又没有抛弃 Java 这个强大的平台，它运行在 Java 虚拟机 (Java Virtual Machine) 之上，轻松实现和丰富的 Java 类库互联互通。它既支持面向对象的编程方式，又支持函数式编程。它写出的程序像动态语言一样简洁，但事实上它确是严格意义上的静态语言。Scala 就像一位武林中的集大成者，将过去几十年计算机语言发展历史中的精萃集于一身，化繁为简
与java 差别
相对于Java而言，Scala的代码更为精简（减低犯错），而且功能更为广泛（Scala其实是Scalable Language 的简称，意为可扩展的语言），许多Scala的特性和语法都是针对Java的不足和弱点来设计的。Scala的特点是有很多函数程式语言的特性（例如ML，Miranda, Scheme，Haskell），譬如惰性求值，list comprehension, type inference, anonymous function, pattern matching 等等，同时也包含 Object-Oriented 的特性（OO 能与 FP 混合使用是 Scala 的亮点）。此外，许多相似于高级编程语言的语法也渗入其中（例如 Python），不仅提高了 Scala 代码的可读性，维护、修改起来也较为省时省力。Scala 与 Java 语法上的明显差异有：不需要分号结尾类型定义开头需大写（与 Haskell 相同）函数定义需 def 开头（与 Python、Ruby 相同）return 可以省略
特点
功能多啊，语法复杂，号称是JVM上的C++
介绍
使用java和scala混合开发可以极大地提高开发效率
添加maven依赖
<dependency>
<groupId>org.scala-langgroupId>
<artifactId>scala-libraryartifactId>
<version>${scala.version}version>
dependency>
添加插件
<plugin>
<groupId>org.scala-toolsgroupId>
<artifactId>maven-scala-pluginartifactId>
<executions>
<execution>
<goals>
<goal>compilegoal>
<goal>testCompilegoal>
goals>
execution>
executions>
<configuration>
<recompileMode>incrementalrecompileMode>
<scalaVersion>${scala.version}scalaVersion>
<launchers>
<launcher>
<id>appid>
<mainClass>xxxxmainClass>
<args>
<arg>-deprecationarg>
args>
<jvmArgs>
<jvmArg>-Xms256mjvmArg>
<jvmArg>-Xmx2048mjvmArg>
jvmArgs>
launcher>
launchers>
configuration>
plugin>
<plugin>
<groupId>org.codehaus.mojogroupId>
<artifactId>build-helper-maven-pluginartifactId>
<version>1.8version>
<executions>
<execution>
<id>add-resourceid>
<phase>initializephase>
<goals>
<goal>add-resourcegoal>
goals>
<configuration>
<resources>
<resource>
<directory>${basedir}/src/main/resourcesdirectory>\
<filtering>truefiltering>
<excludes>
<exclude>**/*.javaexclude>
excludes>
resource>
resources>
configuration>
execution>
<execution>
<id>add-sourceid>
<phase>initializephase>
<goals>
<goal>add-sourcegoal>
goals>
<configuration>
<sources>
<source>${basedir}/src/main/javasource>
<source>${basedir}/src/main/scalasource>
sources>
configuration>
execution>
<execution>
<id>add-test-sourceid>
<phase>initializephase>
<goals>
<goal>add-test-sourcegoal>
goals>
<configuration>
<sources>
<source>${basedir}/src/test/javasource>
sources>
configuration>
execution>
executions>
plugin>
代码示例
- bean
@Entity
class LazyTask {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@BeanProperty
var id: Integer = _
@BeanProperty
var url: String = _
@BeanProperty
var name: String = _
//用例状态: -1未执行 0失败 1成功
@BeanProperty
var state: Integer = _
@BeanProperty
var owner: String = _
@BeanProperty
var resultJson: String = _
@BeanProperty
var executeTimes: Integer = _
@BeanProperty
var executor: Integer = _
@BeanProperty
var gmtCreate: Date = _
@BeanProperty
var gmtModify: Date = _
}
- dao
trait LazyTaskDao extends CrudRepository[LazyTask, Integer] {
def findAll(): List[LazyTask]
def save(t: LazyTask): LazyTask
def findOne(id: Integer): LazyTask
@Query(value = "SELECT * FROM lazy_task where url like '%?1%'", nativeQuery = true)
def listByUrl(url: String): List[LazyTask]
@Query(value = "SELECT * FROM lazy_task where name like '%?1%'", nativeQuery = true)
def listByName(name: String): List[LazyTask]
}
- Controller 示例
@RestController
class LazyTaskController @Autowired()(val lazyTaskDao: LazyTaskDao,
val phantomjsExecutor: PhantomjsExecutor,
val domainConfig: DomainConfig) {
@RequestMapping(value = {
Array("/newTask.do")
})
def newTask_do() = {
new ModelAndView("ylazy/newTask")
}
@RequestMapping(value = {
Array("/ylazy/newTask")
}, method = Array(RequestMethod.POST))
@ResponseBody
def newTask(@ModelAttribute lazyTask: LazyTask) = {
lazyTask.gmtCreate = new Date
lazyTask.gmtModify = new Date
lazyTask.executeTimes = 0
lazyTask.state = -1
lazyTaskDao.save(lazyTask)
}
@RequestMapping(value = {
Array("/list.do")
})
def list_do(model: Model) = {
model.addAttribute("lazyTaskList", lazyTaskDao.findAll())
model.addAttribute("domainName", domainConfig.getDomainName)
model.addAttribute("port", domainConfig.getPort)
new ModelAndView("ylazy/list")
}
/**
* 获取一条任务记录
*
* @param id
* @return
*/
@RequestMapping(value = {
Array("/lazytask")
}, method = Array(RequestMethod.GET))
@ResponseBody
def findOne(@RequestParam(value = "id") id: Integer) = lazyTaskDao.findOne(id)
/**
* 获取一条任务记录的返回json
*
* @param id
* @return
*/
@RequestMapping(value = {
Array("/result/{id}")
}, method = Array(RequestMethod.GET))
@ResponseBody
def findResultJson(@PathVariable(value = "id") id: Integer) = lazyTaskDao.findOne(id).resultJson
/**
* 执行任务
* @param id
* @return
*/
@RequestMapping(value = {
Array("/ylazy/runTask")
}, method = Array(RequestMethod.GET))
@ResponseBody
def runTask(@RequestParam(value = "id") id: Integer) = {
phantomjsExecutor.ylazyById(id)
}
@RequestMapping(value = {
Array("/ylazy")
}, method = Array(RequestMethod.GET))
@ResponseBody
def ylazy(@RequestParam(value = "url") url: String) = phantomjsExecutor.ylazy(url)
}