JsonSchemaFactory.getSchema not thread safe

[mpayne-coveo]

We have a service that uses the same caching mechanism/JsonSchemaFactory to load in JSON schemas, then validate against them as it handles requests in a multithreaded way. Lately, we've been seeing a lot of ConcurrentModificationExceptions when two requests are simultaneously handled and trying to retrieve schemas with the stack trace-

java.util.ConcurrentModificationException: null
	at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1221)
	at com.networknt.schema.JsonSchemaFactory.findMetaSchemaForSchema(JsonSchemaFactory.java:350)
	at com.networknt.schema.JsonSchemaFactory.getSchema(JsonSchemaFactory.java:433)
	at com.networknt.schema.JsonSchemaFactory.getSchema(JsonSchemaFactory.java:462)

We're using version 1.0.87 of json-schema-validator. Let me know if you need further details

[mpayne-coveo]

The fix, I believe, should be as simple as converting jsonMetaSchemas from a HashMap to a ConcurrentHashMap-

json-schema-validator/src/main/java/com/networknt/schema/JsonSchemaFactory.java

Line 51 in e86c817

private final Map<String, JsonMetaSchema> jsonMetaSchemas = new HashMap<String, JsonMetaSchema>();