Jackson JSON List with Object Type

Question

I have to serialize JSON from a list of Objects. The resulting JSON has to look like this:

{
    \"status\": \"success\",
    \"models\": [
        {
                


        

Answer 1

Another approach is using StdConverter class. Here is a working (abbreviated) example:

// MyParentObject.java
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

public class MyParentObject {
  @JsonSerialize(converter = ChildListToString.class)
  @JsonDeserialize(converter = StringToChildList.class)
  @JsonProperty
  public List myChildren;
}

// ChildListToString.java

import com.fasterxml.jackson.databind.util.StdConverter;

import java.util.List;
import java.util.stream.Collectors;

public class ChildListToString extends StdConverter, String> {
  @Override
  public String convert(List value) {
    // this is just as effective as using Jackson "write array"
    // Try-Catch omitted for brevity
    StringBuilder builder = new StringBuilder("[");
    value.stream().map(value -> new ObjectMapper().writeValue(value)).forEach(urnStr -> {
      if(builder.length() > 1) {
        builder.append(", ");
      }

      builder.append("\"").append(urnStr).append("\"");
    });

    builder.append("]");

    return builder.toString();
  }
}

// StringToChildList.java

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.util.StdConverter;


import java.io.IOException;
import java.net.URISyntaxException;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class StringToChildList extends StdConverter> {

  @Override
  public List convert(String value) {
    // try - catch omitted here for brevity
      List strings = new ObjectMapper().readValue(value, new TypeReference>() {});
      return strings.stream()
          .map(string -> {
            return new ObjectMapper().readValue(string, AChildObject.class)
          }).collect(Collectors.toList());

  }
}

I like this because it gives you control of serialization and deserialization separately.