Error Converting jcas object to json object (Infinite recursion)

Question

I am trying to convert a JCas object (org.apache.uima.jcas.JCas) to json string using jackson ObjectMapper as following.

public Map<String, List<CuiResponse>> process(final String text) throws ServletException {
        JCas jcas = null;
        Map<String, List<CuiResponse>> resultMap = null;
        if (text != null) {
            try {
                jcas = _pool.getJCas(-1);
                jcas.setDocumentText(text);
                _engine.process(jcas);

                ObjectMapper mapper = new ObjectMapper();
                String jsonString = mapper.writeValueAsString(jcas);


                resultMap = formatResults(jcas);
                _pool.releaseJCas(jcas);
            } catch (Exception e) {
                throw new ServletException(e);
            }
        }
        return resultMap;
    }

But I am getting Infinite recursion exception as below

"timestamp": "2020-02-04T10:41:33.342+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Infinite recursion (StackOverflowError) (through reference chain: org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org.apache.uima.cas.impl.TypeSystemImpl[\"features\"]->org.apache.uima.cas.impl.FeatureImpl[\"range\"]->org.apache.uima.cas.impl.TypeImpl[\"typeSystem\"]->org

Can anybody suggest a solution?

Answer 1

UIMA CAS objects are not designed to be directly serializable by standard mechanisms such as Java Serialization, Jackson or similar libraries.

But the UIMA framework itself knows how to convert a CAS object to/from a number of serialization formats (some write-only):

• UIMA CAS XMI (read/write)
• UIMA Binary CAS (several variations, read/write)
• Java Serialized CAS (through an indirection)
• UIMA CAS JSON (write-only)
• UIMA XCAS (read/write)

For more information on supported formats, check out CasIOUtils.