I got a Sql table with these fields:
id uniqueidentifier primary key,
<--Omitting extra fields -->
metadata nvarchar(max)
Which I also have a Entity mapped to it:
@Data
public class GenericEntity implements Serializable {
@Id
@GeneratedValue(generator = "uuid2")
@GenericGenerator(name = "uuid2", strategy = "org.hibernate.id.UUIDGenerator")
@Type(type = "uuid-char")
private UUID id;
<--Omitting extra properties -->
@Type(type = "string")
private JsonNode metadata;
}
The second field that is a JsonNode needs to be able to accept different types of json and store it in the table as a String.
How can I go about converting a JsonNode field and store it in the DB as a String then when I read from the table it converts the String back to a JsonNode?
Payload:
{
"id": "db8e8d4b-eee2-4507-bf30-f55c3f948724",
<-- Omitting extra properties -->
"metadata": {
"description": "Sample",
"location": "Stack Overflow"
}
}
Right now everytime I try to save it I get the error:
Could not determine type for: com.fasterxml.jackson.databind.JsonNode, at table: table_name, for columns: [org.hibernate.mapping.Column(metadata)]
I followed these instructions: https://www.baeldung.com/hibernate-custom-types
Created a SqlTypeDescriptor
public class JsonNodeStringType extends AbstractSingleColumnStandardBasicType<JsonNode> implements DiscriminatorType<JsonNode> {
public static final JsonNodeStringType INSTANCE = new JsonNodeStringType();
public JsonNodeStringType() {
super(VarcharTypeDescriptor.INSTANCE, JsonNodeStringJavaDescriptor.INSTANCE);
}
@Override
public String getName() {
return "jsonnode";
}
@Override
public JsonNode stringToObject(String xml) {
return fromString(xml);
}
@Override
public String objectToSQLString(JsonNode value, Dialect dialect) {
return '\'' + toString(value) + '\'';
}
}
Then I created a Java Type Descriptor:
public class JsonNodeStringJavaDescriptor extends AbstractTypeDescriptor<JsonNode> {
public static final ObjectMapper mapper = new ObjectMapper();
public static final JsonNodeStringJavaDescriptor INSTANCE = new JsonNodeStringJavaDescriptor();
public JsonNodeStringJavaDescriptor() {
super(JsonNode.class, ImmutableMutabilityPlan.INSTANCE);
}
@Override
public String toString(JsonNode value) {
try {
return mapper.writeValueAsString(value);
} catch (JsonProcessingException e) {
throw new IllegalArgumentException("The given JsonNode object value: " + value + " cannot be transformed to a String", e);
}
}
@Override
public JsonNode fromString(String string) {
try {
return mapper.readTree(string);
} catch (JsonProcessingException e) {
throw new IllegalArgumentException("The given string value: " + string + " cannot be transformed to JsonNode object", e);
}
}
@Override
public <X> X unwrap(JsonNode value, Class<X> type, WrapperOptions options) {
if (value == null) {
return null;
}
if (String.class.isAssignableFrom(type)) {
return (X) toString(value);
}
throw unknownUnwrap(type);
}
@Override
public <X> JsonNode wrap(X value, WrapperOptions options) {
if (value == null) {
return null;
}
if (String.class.isInstance(value)) {
return fromString(value.toString());
}
throw unknownWrap(value.getClass());
}
Then add the type definition to the entity model
@Data
@TypeDef(name = "jsonnode", typeClass = JsonNodeStringType.class)
public class GenericEntity implements Serializable {
@Id
@GeneratedValue(generator = "uuid2")
@GenericGenerator(name = "uuid2", strategy = "org.hibernate.id.UUIDGenerator")
@Type(type = "uuid-char")
private UUID id;
<--Omitting extra properties -->
@Type(type = "jsonnode")
private JsonNode metadata;
}
If you don't want to manually create these type descriptors you can also follow this article to use a external dependency: https://vladmihalcea.com/sql-server-json-hibernate/
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