POST JSON Rule definition can result in NPE

[andrewazores]

$ https -v --json POST :8181/api/v2/rules name:foo matchExpression="target.annotations.cryostat['JAVA_MAIN']=='demoApp'" eventSpecifier="template=Continuous,type=TARGET"
POST /api/v2/rules HTTP/1.1
Accept: application/json, */*;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Length: 127
Content-Type: application/json
Host: localhost:8181
User-Agent: HTTPie/2.4.0
name: foo

{
    "eventSpecifier": "template=Continuous,type=TARGET",
    "matchExpression": "target.annotations.cryostat['JAVA_MAIN']=='demoApp'"
}


HTTP/1.1 500 Internal Server Error
content-encoding: gzip
content-length: 103
content-type: application/json

{
    "data": {
        "reason": null
    },
    "meta": {
        "status": "Internal Server Error",
        "type": "text/plain"
    }
}

I sent a POST /api/v2/rules and incorrectly formatted my request, so the name key was not included in the JSON body (instead, it was sent as an HTTP header). This resulted in an HTTP 500:

Aug 12, 2021 7:28:28 PM io.cryostat.core.log.Logger error
SEVERE: Exception thrown
io.cryostat.net.web.http.api.v2.ApiException: Internal Server Error
Caused by: java.lang.NullPointerException
	at io.cryostat.rules.Rule$Builder.from(Rule.java:234)
	at io.cryostat.util.RuleDeserializer.deserialize(RuleDeserializer.java:58)
	at io.cryostat.util.RuleDeserializer.deserialize(RuleDeserializer.java:51)
	at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:69)
	at com.google.gson.Gson.fromJson(Gson.java:932)
	at com.google.gson.Gson.fromJson(Gson.java:897)
	at com.google.gson.Gson.fromJson(Gson.java:846)
	at com.google.gson.Gson.fromJson(Gson.java:817)
	at io.cryostat.net.web.http.api.v2.RulesPostHandler.handle(RulesPostHandler.java:144)
	at io.cryostat.net.web.http.api.v2.AbstractV2RequestHandler.handle(AbstractV2RequestHandler.java:114)
	at io.cryostat.net.web.http.api.v2.AbstractV2RequestHandler.handle(AbstractV2RequestHandler.java:68)
	at io.vertx.ext.web.impl.BlockingHandlerDecorator.lambda$handle$0(BlockingHandlerDecorator.java:48)
	at io.vertx.core.impl.ContextImpl.lambda$executeBlocking$2(ContextImpl.java:313)
	at io.vertx.core.impl.TaskQueue.run(TaskQueue.java:76)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:829)

Aug 12, 2021 7:28:28 PM io.cryostat.core.log.Logger info
INFO: (10.0.2.100:60442): POST /api/v2/rules 500 4ms

This should have instead been a 400.