[scala]50行实现web表单验证器

思路是这样，每个表单实现Validatable特质。这个特质要求实现返回一个属性名到验证器列表的映射。

表单验证器执行时首先获取表单所有的属性（除去class），然后遍历这个映射，运行字段对应的验证器变成响应的验证错误（如果有的话），否则最后是个空集合。

FormValidatorRunner（代码最下方）是测试类，执行结果是
Map(name -> List(ValidateError(default.notBlank,List())))

代码如下：

import scala.collection.Traversable

case class ValidateError(messageCode: String, 
  messageArguments: Traversable[Any] = List[Any]())

trait FieldRule {
  def apply(form: Validatable, propertyValue: Option[Any]): Option[ValidateError]
}

object NotBlankFieldRule extends FieldRule {
  def apply(form: Validatable, propertyValue: Option[Any]) = propertyValue match {
    case Some(value) if value.toString.trim.length > 0 => None
    case _ => Some(ValidateError(“default.notBlank”))
  }
}

trait Validatable {
  def getRules(): Map[String, Traversable[FieldRule]]
}

class FormError(fieldErrors: Map[String, Traversable[ValidateError]]) {
  def hasError(): Boolean = fieldErrors.isEmpty
  override def toString = fieldErrors.toString
}

object FormValidator {
  def apply(form: Validatable): FormError = {
    val props = getProps(form)
    new FormError(form.getRules.map{
      case (fieldName, rules) => (fieldName, 
        rules.flatMap(_.apply(form, props.get(fieldName))))
    })
  }

  private def getProps(obj: Any): Map[String, Any] = {
    java.beans.Introspector.getBeanInfo(
        obj.getClass).getPropertyDescriptors.flatMap{ d => 
      Option(d.getReadMethod).map(getter => (d.getName, getter.invoke(obj)))
    }.toMap – “class”
  }
}

object FormValidatorRunner {

  class Person(id: Long, name: String) extends Validatable {
    def getId(): Long = id
    def getName(): String = name
    def getRules = Map(“name” -> List(NotBlankFieldRule))
  }

  def main(args: Array[String]): Unit = {
    println(FormValidator.apply(new Person(1L, “”)))
  }
}

import scala.collection.Traversable

case class ValidateError(messageCode: String,

messageArguments: Traversable[Any] = List[Any]())

trait FieldRule {

def apply(form: Validatable, propertyValue: Option[Any]): Option[ValidateError]

}

object NotBlankFieldRule extends FieldRule {

def apply(form: Validatable, propertyValue: Option[Any]) = propertyValue match {

case Some(value) if value.toString.trim.length > 0 => None

case _ => Some(ValidateError(“default.notBlank”))

}

trait Validatable {

def getRules(): Map[String, Traversable[FieldRule]]

}

class FormError(fieldErrors: Map[String, Traversable[ValidateError]]) {

def hasError(): Boolean = fieldErrors.isEmpty

override def toString = fieldErrors.toString

}

object FormValidator {

def apply(form: Validatable): FormError = {

val props = getProps(form)

new FormError(form.getRules.map{

case (fieldName, rules) => (fieldName,

rules.flatMap(_.apply(form, props.get(fieldName))))

})

}

private def getProps(obj: Any): Map[String, Any] = {

java.beans.Introspector.getBeanInfo(

obj.getClass).getPropertyDescriptors.flatMap{ d =>

Option(d.getReadMethod).map(getter => (d.getName, getter.invoke(obj)))

}.toMap – “class”

}

object FormValidatorRunner {

class Person(id: Long, name: String) extends Validatable {

def getId(): Long = id

def getName(): String = name

def getRules = Map(“name” –> List(NotBlankFieldRule))

}

def main(args: Array[String]): Unit = {

println(FormValidator.apply(new Person(1L, “”)))

}