java – 使用hibernate将Json数据存储到Mysql 5.7数据库或从中检索Json数据

我将开始一个项目,我需要生成动态谷歌表单.这个项目的要求是我需要使用mysql 5.7,以便我可以使用json数据类型来存储/检索json数据.我很好.我知道,有可能使用HQL.但我无法弄清楚如何使用对象关系映射实现Hibernate？

有任何想法吗 ？

提前致谢 ！

解决方法:

最近我解决了类似的任务.我想现在为时已晚,但也许有人觉得这很有用.

简短回答：您应该创建必须实现org.hibernate.usertype.UserType接口的类(如“com.test.MyJsonType”),其中nullSafeGet方法应将JSON反序列化为java对象(使用Jackson),nullSafeSet将POJO序列化为JSON和一些其他辅助方法.

然后你应该扩展MySQLDialect并注册新的列类型“json”.

最后,您可以通过@Type(type =“com.test.MyJsonType”)注释实体字段,该字段应映射到MySQL json列.

如果您不希望使用包名称写入类型,也可以阅读@TypeDef here.

例如：

public class MyJsonType implements UserType {

@Override
public int[] sqlTypes() {
    return new int[] { Types.VARCHAR };
}

@Override
public Class<Characteristics> returnedClass() {
    return Characteristics.class;
}

@Override
public Object nullSafeGet(final ResultSet rs, final String[] names, final SessionImplementor session, final Object owner)
        throws HibernateException, SQLException {
    final String cellContent = rs.getString(names[0]);
    if (cellContent == null) {
        return null;
    }
    try {
        final ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        return mapper.readValue(cellContent.getBytes("UTF-8"), returnedClass());
    } catch (final Exception ex) {
        throw new RuntimeException("Failed to convert String to Invoice: " + ex.getMessage(), ex);
    }
}

@Override
public void nullSafeSet(final PreparedStatement ps, final Object value, final int idx, final SessionImplementor session)
        throws HibernateException, SQLException {
    if (value == null) {
        ps.setNull(idx, Types.VARCHAR);
        return;
    }
    try {
        final ObjectMapper mapper = new ObjectMapper();
        final StringWriter w = new StringWriter();
        mapper.writeValue(w, value);
        w.flush();
        ps.setObject(idx, w.toString(), Types.VARCHAR);
    } catch (final Exception ex) {
        throw new RuntimeException("Failed to convert Invoice to String: " + ex.getMessage(), ex);
    }
}

@Override
public Object deepCopy(final Object value) throws HibernateException {
    try {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(value);
        oos.flush();
        oos.close();
        bos.close();

        ByteArrayInputStream bais = new ByteArrayInputStream(bos.toByteArray());
        return new ObjectInputStream(bais).readObject();
    } catch (ClassNotFoundException | IOException ex) {
        throw new HibernateException(ex);
    }
}

@Override
public boolean isMutable() {
    return true;
}

@Override
public Serializable disassemble(final Object value) throws HibernateException {
    return (Serializable) this.deepCopy(value);
}

@Override
public Object assemble(final Serializable cached, final Object owner) throws HibernateException {
    return this.deepCopy(cached);
}

@Override
public Object replace(final Object original, final Object target, final Object owner) throws HibernateException {
    return this.deepCopy(original);
}

@Override
public boolean equals(Object x, Object y) throws HibernateException {
    return Objects.equals(x, y);
}

@Override
public int hashCode(Object x) throws HibernateException {
    return Objects.hashCode(x);
}

}

POJO课程：

public class Characteristics implements Serializable {

private String field;

public String getField() {
    return field;
}

public void setField(String field) {
    this.field= field;
}

@Override
public boolean equals(Object obj) {

    if (obj == null) return false;
    if (getClass() != obj.getClass()) return false;
    final Characteristics other = (Characteristics) obj;
    return Objects.equals(this.field, other.field);

}

@Override
public int hashCode() {

    return Objects.hash(this.field);

}
}

注册新列类型：

public class JsonMySQLDialect extends MySQLDialect {

public JsonMySQLDialect() {
    this.registerColumnType(Types.VARCHAR, "json");
}

}

使用：

@Entity
@Table(name = "Table")
public class TableClass {
...
@Column
@Type(type = "com.test.MyJsonType")
protected Characteristics characteristics;
...
}

标签：mysql-5-7,java,json,hibernate
来源： https://codeday.me/bug/20191005/1855464.html