如何使用H2，JPA和Hibernate映射JSON列 [英] How to map a JSON column with H2, JPA, and Hibernate

问题描述

我在应用程序MySQL 5.7中使用，并且具有JSON列.当我尝试运行集成测试时，由于H2数据库无法创建表，因此无法进行测试.这是错误:

I use in application MySQL 5.7 and I have JSON columns. When I try running my integration tests don't work because the H2 database can't create the table. This is the error:

2016-09-21 16:35:29.729 ERROR 10981 --- [           main] org.hibernate.tool.hbm2ddl.SchemaExport  : HHH000389: Unsuccessful: create table payment_transaction (id bigint generated by default as identity, creation_date timestamp not null, payload json, period integer, public_id varchar(255) not null, state varchar(255) not null, subscription_id_zuora varchar(255), type varchar(255) not null, user_id bigint not null, primary key (id))
2016-09-21 16:35:29.730 ERROR 10981 --- [           main] org.hibernate.tool.hbm2ddl.SchemaExport  : Unknown data type: "JSON"; SQL statement:

这是实体类.

@Table(name = "payment_transaction")
public class PaymentTransaction extends DomainObject implements Serializable {

    @Convert(converter = JpaPayloadConverter.class)
    @Column(name = "payload", insertable = true, updatable = true, nullable = true, columnDefinition = "json")
    private Payload payload;

    public Payload getPayload() {
        return payload;
    }

    public void setPayload(Payload payload) {
        this.payload = payload;
    }
}

以及子类:

public class Payload implements Serializable {

    private Long userId;
    private SubscriptionType type;
    private String paymentId;
    private List<String> ratePlanId;
    private Integer period;

    public Long getUserId() {
        return userId;
    }

    public void setUserId(Long userId) {
        this.userId = userId;
    }

    public SubscriptionType getType() {
        return type;
    }

    public void setType(SubscriptionType type) {
        this.type = type;
    }

    public String getPaymentId() {
        return paymentId;
    }

    public void setPaymentId(String paymentId) {
        this.paymentId = paymentId;
    }

    public List<String> getRatePlanId() {
        return ratePlanId;
    }

    public void setRatePlanId(List<String> ratePlanId) {
        this.ratePlanId = ratePlanId;
    }

    public Integer getPeriod() {
        return period;
    }

    public void setPeriod(Integer period) {
        this.period = period;
    }

}

此转换器可插入数据库:

And this converter for insert in database:

public class JpaPayloadConverter implements AttributeConverter<Payload, String> {

    // ObjectMapper is thread safe
    private final static ObjectMapper objectMapper = new ObjectMapper();

    private Logger log = LoggerFactory.getLogger(getClass());

    @Override
    public String convertToDatabaseColumn(Payload attribute) {
        String jsonString = "";
        try {
            log.debug("Start convertToDatabaseColumn");

            // convert list of POJO to json
            jsonString = objectMapper.writeValueAsString(attribute);
            log.debug("convertToDatabaseColumn" + jsonString);

        } catch (JsonProcessingException ex) {
            log.error(ex.getMessage());
        }
        return jsonString;
    }

    @Override
    public Payload convertToEntityAttribute(String dbData) {

        Payload payload = new Payload();
        try {
            log.debug("Start convertToEntityAttribute");

            // convert json to list of POJO
            payload = objectMapper.readValue(dbData, Payload.class);
            log.debug("JsonDocumentsConverter.convertToDatabaseColumn" + payload);

        } catch (IOException ex) {
            log.error(ex.getMessage());
        }
        return payload;

    }
}

推荐答案

在提出问题后，H2中添加了对JSON的支持，版本为1.4.200(2019-10-14).

JSON support was added to H2 after the question was asked, with version 1.4.200 (2019-10-14).

但是，您在数据库中很少需要JSON数据类型.JSON本质上只是一个可能很长的字符串，因此您可以使用大多数数据库都可用的CLOB.

However, you rarely need a JSON data type in a database. JSON essentially is just a potentially very long string, so you can use CLOB which is available on most databases.

如果需要对它们进行操作的SQL函数，并且仅在数据库坚持其JSON函数对JSON类型而不是CLOB进行操作时，才需要JSON数据类型.但是，这些功能往往依赖于数据库.

You do need the JSON data type if you need an SQL function that operates on them, and then only if the database insists that its JSON functions operate on a JSON type instead of on a CLOB. Such functions tend to be database-dependent though.

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