jjval

Java JSON/YAML/XML validator

A standalone jar that drives several JSON Schema validators - justify, everit, networknt, json-sKema, and jsonschemafriend - plus W3C XSD and DTD-based XML validation. Having multiple engines in one command makes it easy to cross-check how different implementations judge the same document and schema.

usage

usage: jjval <mode> [-s schema] [-d dtd] [--draft 04|06|07|2019|2020] [-nv] [-q] file...
  exactly one mode must be given:
    -vj         validate json with justify (jakarta.json)
    -ve         validate json with everit (org.json)
    -vn         validate json with networknt (jackson)
    -vk         validate json with json-sKema (draft 2020-12 only)
    -vf         validate json with jsonschemafriend
    -vy         validate yaml with networknt (jackson-dataformat-yaml)
    -vx         validate xml against a dtd given with -d
    -vs         validate xml against a w3c xsd given with -s
    -pj         parse only (passthrough) with justify (jakarta.json)
    -pe         parse only (passthrough) with everit (org.json)
    -pn         parse only (passthrough) with networknt (jackson)
  options:
    -s (schema) JSON schema (or .xsd for -vs) to validate against
    -d (dtd)    DTD file to validate against (used by -vx)
    --draft (04|06|07|2019|2020)
                dialect to assume when the schema has no $schema keyword
    -nv         don't show version
    -q          quiet mode - no output, run only for the exit code
    -h          show this help
  exit: 0=ok 1=syntax error 2=validation error 3=bad schema 4=file i/o 5=usage

Findings (syntax errors, schema violations) go to stdout; progress and summary messages go to stderr, so the two streams can be redirected independently.

exit codes

code	meaning
0	success ? no syntax and no validation problems
1	syntax error in an input document
2	at least one schema/DTD/XSD validation problem
3	the supplied schema could not be parsed or understood
4	an input file could not be read
5	command line usage error

The exit code reflects the first problem category found; all supplied files are always processed.

engine comparison

flag	library	draft support	default dialect
-vj	justify	04 / 06 / 07	from $schema, else 07
-ve	everit	04 / 06 / 07	04 (use --draft 07)
-vn	networknt	04 / 06 / 07 / 2019 / 2020	2020-12
-vk	json-sKema	2020-12 only	2020-12
-vf	jsonschemafriend	03 / 04 / 06 / 07 / 2019 / 2020	from $schema, else 2020
-vy	networknt + YAML	same as -vn	2020-12
-vx	JDK SAX parser	DTD	n/a
-vs	JDK XML schema	W3C XSD	n/a

Use --draft to pin the dialect when comparing engines against the same schema that has no $schema keyword (especially -ve which defaults to draft-04 and ignores modern keywords like const without it).

examples

Validate JSON documents against a JSON schema:

java -jar jjval.jar -vj -s schema.json file1.json file2.json

Cross-check two engines on the same file:

java -jar jjval.jar -vn --draft 07 -s schema.json data.json
java -jar jjval.jar -vj --draft 07 -s schema.json data.json

Validate YAML against a JSON schema:

java -jar jjval.jar -vy -s schema.json data.yaml

Validate XML against a DTD or XSD:

java -jar jjval.jar -vx -d foo.dtd   file.xml
java -jar jjval.jar -vs -s schema.xsd file.xml

Parse only (check well-formedness without a schema):

java -jar jjval.jar -pj file.json

Use in a shell script silently:

java -jar jjval.jar -q -vn -s schema.json data.json || echo "invalid"

building

mvn verify

mvn verify builds the shaded jar and runs the CLI integration tests defined in pom.xml (maven-antrun-plugin, execution cli-test). Every case runs the jar as a subprocess and asserts its exit code, stdout and stderr against the fixtures in src/test/resources/ (<mode>.expected.<case>.<stream>.txt).

After an intentional output change, regenerate all fixtures with:

mvn package && ./src/test/regenerate-expected.sh

The script prints the observed exit code of every case so the expected= attributes in pom.xml can be kept in sync.