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If you're using Java Chronicle it might be a Cleanup problem. Either add @ignore to the test or delete the memory map file and do it again.
Rather than generating JSON by string concatenation, which is pretty much guaranteed to give you functionality and security issues, I recommend using a JSON library instead. We use Jersey in JIRA but any would do.
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com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'Hello': was expecting ('true', 'false' or 'null') at [Source: java.io.StringReader@4983a458; line: 1, column: 6]