This documentation is for the unreleased GraalVM version.Download Early Access Builds from GitHub.

URL Protocols in Native Image

URL Protocols in Native Image can be divided into three classes:

  • supported and enabled by default
  • supported and disabled by default
  • HTTPS support

URL Protocols that are supported and enabled by default will be included into every generated native binary. Currently, file and resource are the only supported URL protocols enabled by default.

There are URL Protocols that are supported but not enabled by default when building a native binary. They must be enabled during build time by using the --enable-url-protocols=<protocols> option on the command line. The option accepts a list of comma-separated protocols.

The rationale behind enabling protocols on-demand is that you can start with a minimal binary and add features as you need them. This way your binary will only include the features you use, which helps keep the overall size small. Currently http and https are the only URL protocols that are supported and can be enabled on demand. They can be enabled using the --enable-http and --enable-https command-line options.

HTTPS Support #

Support for the https URL protocol relies on the Java Cryptography Architecture (JCA) framework. Thus enabling https will add the code required by the JCA to the generated binary, including statically linked native libraries that the JCA may depend on. See the documentation on security services for more details.

No other URL protocols are currently tested. They can still be enabled using --enable-url-protocols=<protocols>, however they might not work as expected.

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