NPE when passing null value to Request.param

[mperktold]

Jetty version(s)
Jetty 12.0.10

Jetty Environment
core

Java version/vendor (use: java -version)
openjdk version "21.0.3" 2024-04-16 LTS
OpenJDK Runtime Environment Temurin-21.0.3+9 (build 21.0.3+9-LTS)
OpenJDK 64-Bit Server VM Temurin-21.0.3+9 (build 21.0.3+9-LTS, mixed mode, sharing)

OS type/version
Windows 11

Description
When passing null as a query parameter value to Request.param, a NullPointerException is thrown. It happens when the value is wrapped in a List using List.of, which doesn't like null values.

I don't think this is intentional. With Jetty 11, null values were allowed. Also, the value is passed to a private method urlEncode, which allows null and is only used for query parameters:

jetty.project/jetty-core/jetty-client/src/main/java/org/eclipse/jetty/client/transport/HttpRequest.java

Line 339 in 803fe5c

query += "&" + urlEncode(name) + "=" + urlEncode(value);

How to reproduce?

var httpClient = new HttpClient();
httpClient.start();
System.out.println(
    httpClient.newRequest("https://google.com/search")
        .param("q", null)
        .send()
);
httpClient.stop();

When running the above code with Jetty 12, it throws the following exception:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:233)
	at java.base/java.util.ImmutableCollections$List12.<init>(ImmutableCollections.java:563)
	at java.base/java.util.List.of(List.java:937)
	at org.eclipse.jetty.util.Fields$Field.<init>(Fields.java:366)
	at org.eclipse.jetty.util.Fields.lambda$add$0(Fields.java:225)
	at java.base/java.util.HashMap.compute(HashMap.java:1324)
	at org.eclipse.jetty.util.Fields.add(Fields.java:221)
	at org.eclipse.jetty.client.transport.HttpRequest.param(HttpRequest.java:334)
	at org.eclipse.jetty.client.transport.HttpRequest.param(HttpRequest.java:329)
	...

It works fine with Jetty 11 though.

[lorban]

This does look like a regression that we should fix.

Thanks for the report!