问题备忘: class path resource [xx] cannot be resolved to absolute file path because it does not reside

问题描述
测试服务的版本是Spring Cloud Dalston.SR5
在Spring Boot中配置https时，代码如下：

    @Bean
    @ConditionalOnExpression("#{ ${self.https.enable:false}}")
    public EmbeddedServletContainerFactory servletContainer() {
        TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
        tomcat.addAdditionalTomcatConnectors(createSslConnector());
        return tomcat;
    }

    private Connector createSslConnector() {
        Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");
        Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();

        ClassPathResource resource = new ClassPathResource(".keystore");
        try {
            connector.setScheme("https");
            connector.setSecure(true);
            connector.setPort(port);
            protocol.setSSLEnabled(true);
            protocol.setKeystoreFile(resource.getFile().getAbsolutePath());
            protocol.setKeystorePass(keystorePass);
            protocol.setKeyAlias(keyAlias);
            protocol.setKeyPass(keyPass);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return connector;
    }

以上代码在我们idea中运行服务时，可以正常执行。但是将服务打包成可执行jar的包，以jar服务运行服务时，抛出以下错误：

java.io.FileNotFoundException: class path resource [.keystore] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/D:/tmp/interface
e-1.0-SNAPSHOT.jar!/BOOT-INF/classes!/.keystore
        at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:215)
        at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:53)

出现以上问题的原因：
打包后Spring无法使用resource.getFile()访问JAR中的路径的文件，必须使用resource.getInputStream()。

修正代码：
通过resource.getInputStream()获取证书文件，然后存储到临时文件，最后Http11NioProtocol 实例通过这个临时文件的路径传入值，这样此Http11NioProtocol 实例可以获取此证书文件。

private Connector createSslConnector() {
      Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");
      Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();

      ClassPathResource resource = new ClassPathResource(".keystore");
      // 临时目录
      String tempPath =System.getProperty("java.io.tmpdir") + System.currentTimeMillis()+".keystore";
      File f = new File(tempPath);
      logger.info(".keystore目录临时存储路径" + tempPath);

      try {
          // 将key的值转存到临时文件
          IOUtils.copy(resource.getInputStream(),new FileOutputStream(f));
          connector.setScheme("https");
          connector.setSecure(true);
          connector.setPort(port);
          protocol.setSSLEnabled(true);
          // 指向临时文件
          protocol.setKeystoreFile(f.getAbsolutePath());
          protocol.setKeystorePass(keystorePass);
          protocol.setKeyAlias(keyAlias);
          protocol.setKeyPass(keyPass);
      } catch (IOException e) {
          e.printStackTrace();
      }

      return connector;
  }