如何将 Postgres JSONB 数据类型与 JPA 一起使用？

Question

Im not finding a way to map the JSON and JSONB datatypes from PostgreSQL using JPA (EclipseLink). Is some one using this datatypes with JPA and can give me some working examples?

Answer 1

All the answers helped me to reach the final solution that is ready for JPA and not EclipseLink or Hibernate specifically.

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import javax.json.Json;
import javax.json.JsonObject;
import javax.persistence.Converter;
import org.postgresql.util.PGobject;

@Converter(autoApply = true)
public class JsonConverter implements javax.persistence.AttributeConverter<JsonObject, Object> {

  private static final long serialVersionUID = 1L;
  private static ObjectMapper mapper = new ObjectMapper();

  @Override
  public Object convertToDatabaseColumn(JsonObject objectValue) {
    try {
      PGobject out = new PGobject();
      out.setType("json");
      out.setValue(objectValue.toString());
      return out;
    } catch (Exception e) {
      throw new IllegalArgumentException("Unable to serialize to json field ", e);
    }
  }

  @Override
  public JsonObject convertToEntityAttribute(Object dataValue) {
    try {
      if (dataValue instanceof PGobject && ((PGobject) dataValue).getType().equals("json")) {
        return mapper.reader(new TypeReference<JsonObject>() {
        }).readValue(((PGobject) dataValue).getValue());
      }
      return Json.createObjectBuilder().build();
    } catch (IOException e) {
      throw new IllegalArgumentException("Unable to deserialize to json field ", e);
    }
  }
}

Answer 2

Edit: I see now that this is pretty much Hibernate dependent. But perhaps you can find something similar for EclipseLink .

I'll just add what I have as an answer, it originates from another SO answer but whatever. This will map jsonb to JsonObject of Google gson , but you can change it to something else if needed. To change to something else, change nullSafeGet , nullSafeSet and deepCopy methods.

public class JsonbType implements UserType {

    @Override
    public int[] sqlTypes() {
        return new int[] { Types.JAVA_OBJECT };
    }

    @Override
    public Class<JsonObject> returnedClass() {
        return JsonObject.class;
    }

    @Override
    public boolean equals(final Object x, final Object y) {
        if (x == y) {
            return true;
        }
        if (x == null || y == null) {
            return false;
        }
        return x.equals(y);
    }

    @Override
    public int hashCode(final Object x) {
        if (x == null) {
            return 0;
        }

        return x.hashCode();
    }

    @Nullable
    @Override
    public Object nullSafeGet(final ResultSet rs,
                              final String[] names,
                              final SessionImplementor session,
                              final Object owner) throws SQLException {
        final String json = rs.getString(names[0]);
        if (json == null) {
            return null;
        }

        final JsonParser jsonParser = new JsonParser();
        return jsonParser.parse(json).getAsJsonObject();
    }

    @Override
    public void nullSafeSet(final PreparedStatement st,
                            final Object value,
                            final int index,
                            final SessionImplementor session) throws SQLException {
        if (value == null) {
            st.setNull(index, Types.OTHER);
            return;
        }

        st.setObject(index, value.toString(), Types.OTHER);
    }

    @Nullable
    @Override
    public Object deepCopy(@Nullable final Object value) {
        if (value == null) {
            return null;
        }
        final JsonParser jsonParser = new JsonParser();
        return jsonParser.parse(value.toString()).getAsJsonObject();
    }

    @Override
    public boolean isMutable() {
        return true;
    }

    @Override
    public Serializable disassemble(final Object value) {
        final Object deepCopy = deepCopy(value);

        if (!(deepCopy instanceof Serializable)) {
            throw new SerializationException(
                    String.format("deepCopy of %s is not serializable", value), null);
        }

        return (Serializable) deepCopy;
    }

    @Nullable
    @Override
    public Object assemble(final Serializable cached, final Object owner) {
        return deepCopy(cached);
    }

    @Nullable
    @Override
    public Object replace(final Object original, final Object target, final Object owner) {
        return deepCopy(original);
    }
}

To use this, do:

public class SomeEntity {

    @Column(name = "jsonobject")
    @Type(type = "com.myapp.JsonbType") 
    private JsonObject jsonObject;

In addition, you need to set your dialect to indicate that JAVA_OBJECT = jsonb :

registerColumnType(Types.JAVA_OBJECT, "jsonb");

Answer 3

I think I found an analogy to Hibernate's UserType for EclipseLink.

http://www.eclipse.org/eclipselink/documentation/2.6/jpa/extensions/annotations_ref.htm#CHDEHJEB

You have to make a class that implements org.eclipse.persistence.mappings.converters.Converter and does the conversion for you, then use the @Convert annotation on every field where you are using that type.

Answer 4

For anyone looking for a Mysql solution with the JSON column type, here it is. FWIW I am using EclipseLink but this is a pure JPA solution.

@Column(name = "JSON_DATA", columnDefinition="JSON")
@Convert(converter=JsonAttributeConverter.class)
private Object jsonData;

and

@Converter
public class JsonAttributeConverter implements AttributeConverter <Object, String>
{

    private JsonbConfig cfg = new JsonbConfig().withFormatting(true);

    private Jsonb jsonb = JsonbBuilder.create(cfg);
    
    @Override
    public String convertToDatabaseColumn(Object object)
    {      
        if (object == null) return null;

        return jsonb.toJson(object);
    }

    @Override
    public Object convertToEntityAttribute(String value)
    {
        if (value == null) return null;

        return jsonb.fromJson(value, value.getClass());
    }

}