Jackson: is there a way to serialize POJOs directly to treemodel?

Question

I'm looking for a way to directly convert some POJO to a Jackson TreeModel. I know that a translation from POJO-to-JSON-String exists, and TreeModel-to-JSON-String is supported — hovewer I am looking for a POJO-to-TreeModel translation. Is there a way?

The use-case is as follows:

Server-side templating is done with the Java implementation of Mustache. This uses Jackson's TreeModel.
After that, I need a slimmed-down version of the TreeModel on the client-side, so I want to be able to first filter the TreeModel, serialize that to JSON, then send it to the client-side for further processing.

This, ideally, involves two serialization steps. However, in my workaround, I am currently using three — which you can see here:

map = // a map of  pojos with jackson annotations

//pojo >> JSON
StringWriter w = new StringWriter();    
objectmapper.writeValue(new JsonFactory().createJsonGenerator(w), map);
String json = w.toString();
w.close();

//JSON >> Treemodel
JsonNode tree = GenericJcrDTO.mapper.readTree(json);
//filter tree here

//treemodel >>JSON
StringWriter w = new StringWriter();
GenericJcrDTO.mapper.writeValue(new JsonFactory().createJsonGenerator(w), tree);
json = w.toString();
w.close();

Anyone?

One other quick suggestion: instead of using StringWriter, just do 'mapper.writeValueAsString()' (or, to get byte[], 'writeValueAsBytes()') — StaxMan, Aug 07 '11 at 06:19

score 82 · Accepted Answer · edited Aug 19 '21 at 07:13

82

To answer my own question:

JsonNode node = objectMapper.valueToTree(map);

edited Aug 19 '21 at 07:13

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answered Aug 06 '11 at 15:40

Geert-Jan

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Indeed. And in general, 'ObjectMapper.convertValue(sourceOb, dstType)' can be used for various conversions, including POJO to tree case. – StaxMan Aug 07 '11 at 06:18
2

It appears that ObjectMapper.valueToTree wasn't added until version 1.6, so the 'ObjectMapper.convertValue(sourceObj, JsonNode.class)' alternative from @StaxMan is great for those of us that haven't upgraded yet! – Steve Onorato Nov 07 '14 at 00:15
It looks like `valueToTree` just adds the POJO as a `POJONode`, without serializing it into "basic" nodes, so it's not possible to deconstruct, filter, or alter the fields or descendants of the POJO. I'd love to have a simple solution for this... – dirkt Jun 15 '18 at 08:18
2

@dirkt use ObjectNode instead of JsonNode: ```mapper.valueToTree(map)``` – leonidv Feb 09 '20 at 06:27

Jackson: is there a way to serialize POJOs directly to treemodel?

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