Question

我显然缺少一些基本的东西。我有以下Scala代码：

package org.carlskii

import java.io._
import java.security.cert.CertificateFactory
import java.security.Security
import org.bouncycastle.jce.provider._

object Main extends App {

  Security.addProvider(new BouncyCastleProvider)
  val provider = new BouncyCastleProvider
  val in = new FileInputStream("cert.cer")
  val certificateFactory = CertificateFactory.getInstance("X509", provider)
  val certificate = certificateFactory.generateCertificate(file)
  println(certificate.getClass)

}

产生这个：

class org.bouncycastle.jce.provider.X509CertificateObject

所以我有一个Bouncy Castle X509CertificateObject对象。如果我调用certificate.getPublicKey方法，它会正确返回证书的公钥。

但是，如果我调用certificate.getSerialNumber，则会抛出以下错误：

error: value getSerialNumber is not a member of java.security.cert.Certificate
println(certificate.getSerialNumber)

这里有趣的是Scala认为它是java.security.cert.Certificate而不是org.bouncycastle.jce.provider.X509CertificateObject对象。为什么会这样？

Answer 1

generateCertificate方法返回一个Certificate对象，如果您确定要获得org.bouncycastle.jce.provider.X509CertificateObject只是将结果投射到该对象：

package org.carlskii

import java.io._
import java.security.cert.CertificateFactory
import java.security.Security
import org.bouncycastle.jce.provider._

object Main extends App {

  Security.addProvider(new BouncyCastleProvider)
  val provider = new BouncyCastleProvider
  val in = new FileInputStream("cert.cer")
  val certificateFactory = CertificateFactory.getInstance("X509", provider)
  val certificate = certificateFactory.generateCertificate(file).asInstanceOf[X509CertificateObject]
  println(certificate.getClass)

}

Answer 2

方法generateCertificate返回类型证书，因此推断val证书具有类型证书。方法generateCertificate有一个方法签名：

Certificate generateCertificate(InputStream inStream)

当您将此调用的结果分配给val scala编译器时，将推断证书的类型，并且类型为Certificate，即generateCertificate返回的类型。

因此，如果要调用在X509CertificateObject类型上定义的方法，则必须先将其转换为正确的类型：

certificate.asInstanceOf[X509CertificateObject]

从getClass获得的是对象的运行时类。

Scala无法访问对象类

2 个答案: