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I am currently trying to map a swagger.json file to a io.swagger.models.Swagger.class. I've tried to use com.fasterxml.jackson.databind.ObjectMapper.class to solve the issue by :

new ObjectMapper().readValue(file.getInputStream(), Swagger.class)`

but i got this exception:

"InvalidDefinitionException: Cannot construct instance of io.swagger.models.parameters.Parameter (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information at [Source: (FileInputStream); line: 28, column: 21] (through reference chain: io.swagger.models.Swagger["paths"]->java.util.LinkedHashMap["/myPath"]->io.swagger.models.Path["post"]->io.swagger.models.Operation["parameters"]->java.util.ArrayList[0])"

The problem is that the parameters field in Swagger class goes like this :

protected Map<String, Parameter> parameters;

Parameter here is an Interface, so the ObjectMapper doesn't know which class to instantiate (BodyParameter, PathParameter, FormParameter...)

I expect to load a swagger.json file into a Swagger Object.

Thank you for your help.

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2 Answers 2

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Similar to Rayen's answer, you have to register deserialisers. Swagger offers serializers for its objects (e.g. Parameter, Property, Model) in io.swagger.util within io.swagger:swagger-core.

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I found it, I needed to implement Deserializers in order to declare explicitly which class constructor to use. I had problem with Parameter, Model and Property which were all interfaces.

Here is the Code : 

ObjectMapper mapper = new ObjectMapper(); SimpleModule module = new SimpleModule(); module.addDeserializer(io.swagger.models.parameters.Parameter.class, new ParameterDeserializer()); module.addDeserializer(io.swagger.models.Model.class, new ModelDeserializer()); module.addDeserializer(io.swagger.models.properties.Property.class, new PropertyDeserializer()); mapper.registerModule(module);

Just an example to clarify things, I can make it more flexible later :

import java.io.IOException; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.deser.std.StdDeserializer; import io.swagger.models.parameters.BodyParameter; import io.swagger.models.parameters.FormParameter; import io.swagger.models.parameters.Parameter; import io.swagger.models.parameters.PathParameter; import io.swagger.models.parameters.QueryParameter; public class ParameterDeserializer extends StdDeserializer<io.swagger.models.parameters.Parameter> { /** * */ private static final long serialVersionUID = 1L; public ParameterDeserializer() { this(null); } public ParameterDeserializer(Class<?> vc) { super(vc); } @Override public Parameter deserialize(JsonParser parser, DeserializationContext ctxt) throws IOException, JsonProcessingException { final JsonNode node = parser.getCodec().readTree(parser); final ObjectMapper mapper = (ObjectMapper) parser.getCodec(); if (node.get("in").toString().toLowerCase().replaceAll("\"", "").equals("path")) { return mapper.treeToValue(node, PathParameter.class); } else if (node.get("in").toString().toLowerCase().replaceAll("\"", "").equals("body")) { return mapper.treeToValue(node, BodyParameter.class); } else if (node.get("in").toString().toLowerCase().replaceAll("\"", "").equals("query")) { return mapper.treeToValue(node, QueryParameter.class); } else { return mapper.treeToValue(node, FormParameter.class); } } }

Same for the other deserializers. Hope it helps.

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