How to map Postgres JSON data type in DTO and Aggentity class using Springboot and Hibernate

问题

I have a ResponseDto class which looks like as below:

public static class HealthGoalsHighlight {

    @ApiModelProperty(value = "Total number of eligible users")
    private Long totalEligibleUsers;
    @ApiModelProperty(value = "Total number of registered users")
    private Long totalRegisteredUsers;
    @ApiModelProperty(value = "Total number of users with atleast one goal count")
    private Long totalUsersWithGoal;
    @ApiModelProperty(value = "Top goal name selected by user")
    private String topGoal;
    @ApiModelProperty(value = "Bottom goal name selected by user")
    private String bottomGoal;
  }

This DTO was made based upon below table structure:

health_goals
(
  uid BIGSERIAL NOT NULL CONSTRAINT health_goals_pkey primary key,
  employer_key bigint not null,
  total_eligible_users bigint not null,
  total_registered_users bigint not null,
  total_users_with_goal bigint not null,
  top_goal_name varchar(255),
  bottom_goal_name varchar(255),
  created_ts TIMESTAMP NOT NULL DEFAULT NOW(),
  updated_ts TIMESTAMP NOT NULL DEFAULT NOW(),
  created_by varchar(255),
  updated_by varchar(255)
);

Now the table structure has been changed to as below:

health_goals
(
  uid BIGSERIAL NOT NULL CONSTRAINT health_goals_pkey primary key,
  employer_key bigint not null,
  health_goals_metric_value json null,
  created_ts TIMESTAMP NOT NULL DEFAULT NOW(),
  updated_ts TIMESTAMP NOT NULL DEFAULT NOW(),
  created_by varchar(255),
  updated_by varchar(255)
);

Basically now all these columns like total_eligible_users, total_registered_users, total_users_with_goal, top_goal_name, bottom_goal_name wil be consolidated to single columnhealth_goals_metric_value as a JSON data type.

How can I write the response DTO for JSON data type column. Also what changes needs to be done in my AggMapper class.

回答1:

Well one way is by using converter function. You can use the converter function to get values in same format.

Change your orm.xml something like below on your column definition

<basic name="healthGoalsMetricValue">
                <column name="health_goals_metric_value" nullable="true"/>
                <convert converter="path.to.your.HealthGoalsMetricValueConverter"/>
            </basic>

Or if you have java file

aggentity will have following entry

  @Convert(converter = HealthGoalsMetricValueConverter.class)
    private HealthGoalsHighlight healthGoalsHighlight ;

and your class HealthGoalsMetricValue will look something like

//////////////////Edited converter class after comments

       import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
import java.io.IOException;

@Converter
public class HealthGoalsMetricValueConverter implements AttributeConverter<HealthGoalsMetricValue, String> {

private final ObjectMapper mapper = new ObjectMapper();

//And then override like that
@Override
        public String convertToDatabaseColumn(HealthGoalsHighlight healthGoalsMetricValue) {

            try {                
                json = mapper.writeValueAsString(healthGoalsMetricValue);
            } catch (JsonProcessingException exception) {
                throw new JsonProcessingException("Error occurred while object serialization", exception);
            }
            return json;
    }

 //And then override again
@Override
public HealthGoalsMetricValue  convertToEntityAttribute(String healthGoalsMetricValuestr ) {
    HealthGoalsMetricValue  healthGoalsMetricValue  = null;
    try {
        if (healthGoalsMetricValue != null) {
            healthGoalsMetricValue = mapper.readValue(healthGoalsMetricValuestr, HealthGoalsMetricValue.class);
        }
    } catch (Exception exception) {
        throw new Exception("Error occurred while object Deserialization", exception);
    }
    return healthGoalsMetricValue;
}

This all will do the job for you.

回答2:

If you can add additional library have a look at https://github.com/vladmihalcea/hibernate-types project, it's super easy with that.

With this library you will end up with code as simple as this

@Entity
@Table(name = "health_goals")
@TypeDefs({
    @TypeDef(name = "json", typeClass = JsonStringType.class),
    @TypeDef(name = "jsonb", typeClass = JsonBinaryType.class)
})
public class HealthGoal {
    // all other columns
    @Type(type = "json")
    private HealthGoalsHighlight healthGoalsHighlight;

    // getters setters

}

And if using the maven add dependency

<dependency>
  <groupId>com.vladmihalcea</groupId>
  <artifactId>hibernate-types-52</artifactId>
  <version>2.9.10</version> // or newer version
</dependency>

来源：https://stackoverflow.com/questions/62039910/how-to-map-postgres-json-data-type-in-dto-and-aggentity-class-using-springboot-a