从 mysql 数据库获取 JSONArray 使用 Spring 启动 JPA

Question

在我的 mysql 表中有存储“JSONArray”的列

这是 spring-boot 项目中 model class 的一部分。

public class SubQuestions implements Serializable{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "sub_questionId", nullable = false,columnDefinition = "INT(11) UNSIGNED")
    private Integer sub_questionId;

    private JSONArray answers;

}

已经 model class 具有空的构造函数，具有所有字段、getter 和 setter 的构造函数。

这是我的 SubQuestionsRepository 接口。

public interface SubQuestionsRepository extends Serializable,JpaRepository<Questions,Integer>{

}

这是我的 controller class 的一部分。

public class SubQuestionsController implements Serializable{
 private SubQuestionsRepository subquestionsrepository;


    public SubQuestionsController(SubQuestionsRepository subquestionsrepository) {
        super();
        this.SubQuestionsRepository = subquestionsrepository;
    }

    @GetMapping("/getall")
    public  Collection<SubQuestions> getallnestedques(){
        return subquestionsrepository.getactiveques();
    }
}

但是当我调用“getallnestedques()”方法时，它会出现以下错误。

There was an unexpected error (type=Internal Server Error, status=500).
could not deserialize; nested exception is org.hibernate.type.SerializationException: could not deserialize
org.springframework.orm.jpa.JpaSystemException: could not deserialize; nested exception is org.hibernate.type.SerializationException: could not deserialize
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:353)
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:255)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:528)
    at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)
    at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:153)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMeth

我如何解决这个问题？

Answer 1

您可以尝试以下解决方案吗？

需要将answers列声明为Lob ，如下例所示：

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Convert;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Lob;

import org.json.JSONArray;

@Entity
public class SubQuestions implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "sub_questionId", nullable = false,columnDefinition = "INT(11) UNSIGNED")
    private Integer sub_questionId;

    @Lob
    @Column
    @Convert(converter = JSONArrayConverter.class)
    private JSONArray answers;
}

属性转换器JSONArrayConverter在存储到数据库之前将JSONArray object 转换为String并在从数据库读取值后转换为JSONArray ：

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

import org.json.JSONArray;
import org.slf4j.LoggerFactory;

import ch.qos.logback.classic.Logger;

@Converter(autoApply = true)
public class JSONArrayConverter implements AttributeConverter<JSONArray, String> {

    private static final Logger logger = (Logger) LoggerFactory.getLogger(JSONArrayConverter.class);

    @Override
    public String convertToDatabaseColumn(JSONArray array)
    {
        String data = null;
        try
        {
            data = array.toString();
        }
        catch (final Exception e)
        {
            logger.error("JSON writing error", e);
        }

        return data;
    }

    @Override
    public JSONArray convertToEntityAttribute(String data)
    {
        JSONArray array = null;

        try
        {
            array = new JSONArray(data);
        }
        catch (final Exception e)
        {
            logger.error("JSON reading error", e);
        }

        return array;
    }
}