Java返回YAML MIME类型null

Question

Java 8 Files.probeContentType(new File("config.yml").toPath()); returns null . Why java couldn't find yaml mime type, but can find xml as text/xml ? Is there any other way?

foo: bar

Answer 1

The default implementation on Windows uses the registry to find the content type. You would need to create the registry key HKEY_CLASSES_ROOT\\.yml and add a string value underneath it called Content Type that has the value that you want to use as the MIME type. You can save the following as yaml.reg and use it to add the necessary keys for you:

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.yml]
"Content Type"="application/x-yaml"

Alternatively, if you want to use Files.probeContentType(…) but do not want to rely upon the provided default implementation, you can create your own FileTypeDetector :

package com.example;

public class CustomFileTypeDetector extends FileTypeDetector
{
    public CustomFileTypeDetector()
    {
    }

    @Override
    public String probeContentType(Path path)
        throws IOException
    {
        // Some error checking omitted for brevity
        String filename = path.getFileName().toString();

        if (filename.endsWith(".yml") || filename.endsWith(".yaml")) {
            // See https://stackoverflow.com/a/332159/21926
            return "application/x-yaml";
        }

        return null;
    }
}

You will also need to create a file that ServiceLoader can find because that is how it discovers implementations of FileTypeDetector . Assuming maven, you would create a file:

src/main/resources/META-INF/services/java.nio.file.spi.FileTypeDetector

With the following content (based on the example code above):

com.example.CustomFileTypeDetector