jackson3-by-example/streaming-huge-json/README.md

streaming-huge-json

Companion code for the rewritten post Jackson Streaming API and JsonNode (Jackson 3).

A self-contained Maven module (not part of the root build). It generates a 1 GiB JSON array, then counts the ERROR records four ways under fixed -Xmx limits.

Jackson   3.2.4   (tools.jackson.core:jackson-databind, GA on Maven Central 2026-10-18)
JDK       Temurin 25.0.5 (LTS)

Class	What it shows
GenerateHugeJson	Writing 1 GiB with JsonGenerator under -Xmx64m
Scan	stream, hybrid, tree, bind (and the broken hybrid-naive)
NestedTrap	The flat-object loop breaking on nested JSON; skipChildren() fix
TruncatedFile	What a cut-off file does to streaming vs tree
ReadLimits	Default StreamReadConstraints values

cd streaming-huge-json
./scripts/run-all.sh --quick   # small demos only
./scripts/run-all.sh           # also generates target/huge.json (1 GiB, git-ignored) and runs the ladder

Captured output is in output/. Memory figures are from one run on a 2-CPU, 8 GB container; peakUsed is sampled total - free heap and includes garbage not yet collected. Timings vary between runs; the pass/fail pattern per -Xmx is the stable part.

Note on output/bench.txt: the tree -Xmx= 6144 MB KILLED line comes from a separate manual run (the first ladder run printed a blank line for it because the OS killed the JVM, exit 137); scripts/bench.sh now records that case itself.