Spring：如何在 PostgreSQL 中使用 KeyHolder

最近迁移到POSTGRESQL，我试图在db表中创建一个新条目时获得唯一生成的密钥.表screenstable如下所示:

CREATE TABLE screenstable
(
  id serial NOT NULL,
  screenshot bytea,
  CONSTRAINT screen_id PRIMARY KEY (id )
)

将数据插入screenstable的方法如下:

@Autowired NamedParameterJDBCTemplate template;
public int insertImage(ImageBean imageBean){
        String query = "insert into screenstable (screenshot) values (:image)";
        SqlParameterSource data = new BeanPropertySqlParameterSource(imageBean);
        KeyHolder keyHolder = new GeneratedKeyHolder();
        template.update(query, data, keyHolder);
        return keyHolder.getKey().intValue();
    }

ImageBean是

import java.util.Arrays;

public class ImageBean {
    private int id;
    private byte[] image;
    @Override
    public String toString() {
        return "ImageBean [id=" + id + ", image=" + Arrays.toString(image)
                + "]";
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public byte[] getImage() {
        return image;
    }
    public void setImage(byte[] image) {
        this.image = image;
    }
}

但是运行代码会出现以下异常

15:33:20,953 ERROR JsonParseExceptionMapper:15 - org.springframework.dao.InvalidDataAccessApiUsageException: The getKey method should only be used when a single key is returned.  The current key entry contains multiple keys: [{id=3, screenshot=[B@db59df}]
org.springframework.dao.InvalidDataAccessApiUsageException: The getKey method should only be used when a single key is returned.  The current key entry contains multiple keys: [{id=3, screenshot=[B@db59df}]
        at org.springframework.jdbc.support.GeneratedKeyHolder.getKey(GeneratedKeyHolder.java:65)
        at some.project.model.FeedbackDao.insertImage(FeedbackDao.java:20)
        at some.project.rest.FeedsRest.pluginCheck(FeedsRest.java:62)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597).....

同样的代码在MySQL的情况下可以正常运行，但在POSTGRES中使用时，键失败.数据类型serial是导致代码失败的原因，还是我正确使用了主键功能？

请给我一些建议.