修改字段以存储到数据库

本文介绍了修改字段以存储到数据库的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

说我有一个字段content，它是一个json.我想将其存储在数据库中，以便我的域类仅保留1字段. (这更多是大脑的任务；-)

Say I have a field content that is a json. I would like to store it in database so that my domain class keeps only the 1 field only. (It's more of a brain task ;-)

class MyDomain{ def content static constraints = { content nullable: false, blank: false, sqlType: "text" // adapter from JSON to String?? } def beforeInsert(){ content = content.toString() } def beforeUpdate(){ content = content.toString() } def afterInsert(){ content = JSON.parse(content) as JSON } def afterUpdate(){ content = JSON.parse(content) as JSON } def onLoad(){ content = JSON.parse(content) as JSON } }

我希望我的域对象仅公开content，所以我不想使用String contentAsText之类的其他字段，因为它在外部是可见的.

I want my domain object to expose only content so I don't want to use another field like String contentAsText because it would be visible outside.

在整个GORM文档中，我还没有找到如何管理它的方法.我已经尝试过beforeValidate()/beforeInsert()和onLoad()方法，但是没有运气...

In the whole GORM documentation I haven't found a thing how to manage it. I've tried beforeValidate()/beforeInsert() and onLoad() methods but no luck...

在值保持不变之前，我该如何调整它?

How can I adapt the value before it gets persisted?

推荐答案

您可以为JSONElement定义自定义的休眠user-type，如下所述:stackoverflow/a/28655708/607038

You can define a custom hibernate user-type for JSONElement as described here: stackoverflow/a/28655708/607038

在域类约束中:

static constraints = { content type: JSONObjectUserType }

用户类型类别:

import org.grails.web.json.JSONObject import org.hibernate.HibernateException import org.hibernate.engine.spi.SessionImplementor import org.hibernate.type.StandardBasicTypes import org.hibernate.usertype.EnhancedUserType import java.sql.PreparedStatement import java.sql.ResultSet import java.sql.SQLException import java.sql.Types class JSONObjectUserType implements EnhancedUserType, Serializable { private static final int[] SQL_TYPES = [Types.VARCHAR] @Override public int[] sqlTypes() { return SQL_TYPES } @Override public Class returnedClass() { return JSONObject.class } @Override public boolean equals(Object x, Object y) throws HibernateException { if (x == y) { return true } if (x == null || y == null) { return false } JSONObject zx = (JSONObject) x JSONObject zy = (JSONObject) y return zx.equals(zy) } @Override public int hashCode(Object object) throws HibernateException { return object.hashCode() } @Override public Object nullSafeGet(ResultSet resultSet, String[] names, SessionImplementor session, Object owner) throws HibernateException, SQLException { Object jsonObject = StandardBasicTypes.STRING.nullSafeGet(resultSet, names, session, owner) if (jsonObject == null) { return null } return new JSONObject((String) jsonObject) } @Override public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index, SessionImplementor session) throws HibernateException, SQLException { if (value == null) { StandardBasicTypes.STRING.nullSafeSet(preparedStatement, null, index, session) } else { JSONObject jsonObject = (JSONObject) value StandardBasicTypes.STRING.nullSafeSet(preparedStatement, jsonObject.toString(), index, session) } } @Override public Object deepCopy(Object value) throws HibernateException { return value } @Override public boolean isMutable() { return false } @Override public Serializable disassemble(Object value) throws HibernateException { return (Serializable) value } @Override public Object assemble(Serializable cached, Object value) throws HibernateException { return cached } @Override public Object replace(Object original, Object target, Object owner) throws HibernateException { return original } @Override public String objectToSQLString(Object object) { throw new UnsupportedOperationException() } @Override public String toXMLString(Object object) { return object.toString() } @Override public Object fromXMLString(String string) { return new JSONObject(string) } }