所以我正在开发聊天应用程序。我有一部分兴趣是要一次从数据库中检索3个实体。有一个serverDto实体和accountDto实体。每个服务器都有许多帐户,并且帐户中有一个名为“活动”的字段,如果活动= 1表示这是我的帐户。我已经创建了一个名为ServerAccount的POJO,如下所示
class ServerAccount {
@Embedded
var accountDto: AccountDto? = null
// Server and Account have same column "serverId"
@Relation(parentColumn = "serverId", entityColumn = "serverId")
var rUserDto: RUserDto? = null
}
因此,由于我希望每次打开chatRoomActivity都具有一次Contact和ServerAccount,但我希望它们是分开的实体,而不是一个包含许多字段的大对象。我的意思是类似下面的内容
class ContactServerAccount {
@Embedded
var contact: AccountDto? = null
@Embedded
var account: AccountDto? = null
@Embedded
var server: ServerDto? = null
////////////////////////////////////
// OR something like that //
////////////////////////////////////
@Embedded
var serverAccount: ServerAccount = null
@Relation
var contact: AccountDto = null
}
我如何使用给定serverId的serverId和给我联系人的contactId来做到这一点?
如果我理解正确,则可以使用三种方法:完全嵌入(嵌入所有三个表),分层嵌入(联系+ ServerAccount)或有限嵌入(不使用@Relates)
我相信3rd符合您的极简/简化数据,所以类似于:-
class ContactServerAccountLimited {
var serverId: Long = 0
var accountId: Long = 0
@Embedded
var contact: Contact = Contact()
}
如果与:-一起使用>
@Query("SELECT serverId,accountId,contact.* FROM server JOIN account ON accountServerId = serverId JOIN contact ON contactServerId = serverId WHERE active = :active") fun getContactServerAccountLimited(active :Boolean) :List<ContactServerAccountLimited>
示例
使用的实体:-
@Entity(tableName = "server") class Server { @PrimaryKey var serverId: Long? = null; var servername: String? = null; constructor() @Ignore constructor(name: String) { serverId = null servername = name } } @Entity( tableName = "account", foreignKeys = [ ForeignKey( entity = Server::class, parentColumns = ["serverId"], childColumns = ["accountServerId"]) ] ) class Account { @PrimaryKey var accountId: Long? = null var accountServerId: Long? = null var accountName: String? = null var active: Boolean = false constructor() @Ignore constructor(accountName: String, accountServerId: Long) { this.accountName = accountName this.accountServerId = accountServerId this.active = false } } @Entity( tableName = "contact", foreignKeys = [ ForeignKey( entity = Server::class, parentColumns = ["serverId"], childColumns = ["contactServerId"] ) ] ) class Contact { @PrimaryKey var contactId: Long? = null var contactServerId: Long? = null var contactName: String? = null constructor() @Ignore constructor(name: String, serverId: Long) { contactId = null contactName = name contactServerId = serverId } }
POJO的:-
class ContactServerAccount { @Embedded var serverAccount: ServerAccount? = ServerAccount() @Relation(entity = Contact::class,parentColumn = "serverId",entityColumn = "contactServerId") var contact: Contact = Contact() } class ContactServerAccountLimited { var serverId: Long = 0 var accountId: Long = 0 @Embedded var contact: Contact = Contact() }
The Dao:-
@Dao interface AllDao { @Insert fun insertServer(server: Server): Long @Insert fun insertAccount(account: Account): Long @Insert fun insertContact(contact: Contact): Long @Query("UPDATE account SET active = NOT active WHERE accountId = :accountId") fun toggleAccountActiveStatus(accountId: Long) @Query("SELECT * FROM server") fun getAllServers() :List<Server> @Query("SELECT * FROM account") fun getAllAccounts() :List<Account> @Query("SELECT * FROM contact") fun getAllContacts() :List<Contact> @Query("SELECT * FROM server JOIN account ON accountServerId = serverId JOIN contact ON contactServerId = serverId WHERE active = :active") fun getContactServerAccount(active: Boolean) :List<ContactServerAccount> @Query("SELECT serverId,accountId,contact.* FROM server JOIN account ON accountServerId = serverId JOIN contact ON contactServerId = serverId WHERE active = :active") fun getContactServerAccountLimited(active :Boolean) :List<ContactServerAccountLimited> @Query("DELETE FROM server") fun deleteAllServers() :Int @Query("DELETE FROM account") fun deleteAllAccounts() :Int @Query("DELETE FROM contact") fun deleteAllContacts() :Int }
和:-
val allDao = database.allDao(); allDao.deleteAllContacts() allDao.deleteAllAccounts() allDao.deleteAllServers() currentServer = allDao.insertServer(Server("Server 1")) allDao.insertAccount(Account("FRED",currentServer)) allDao.insertAccount(Account("MARY",currentServer)) allDao.insertContact(Contact("C1",currentServer)) currentServer = allDao.insertServer(Server("Server 2")) allDao.insertAccount(Account("JANE",currentServer)) allDao.insertAccount(Account("ANNE",currentServer)) allDao.insertContact(Contact("C2",currentServer)) currentServer = allDao.insertServer(Server("Server 3")) allDao.insertAccount(Account("VERA",currentServer)) allDao.insertAccount(Account("JOHN",currentServer)) allDao.insertContact(Contact("C3",currentServer)) allDao.insertContact(Contact("C4",currentServer)) allDao.toggleAccountActiveStatus(1) var serverList: List<Server> = allDao.getAllServers() for (s: Server in serverList) { Log.d("SERVERINFO","Server ID is " + s.serverId + " Name is " + s.servername) } var accountList = allDao.getAllAccounts() for (a: Account in accountList) { Log.d("ACCOUNTINFO","Account ID is " + a.accountId + " Account Name is " + a.accountName + " Account Server ID is " + a.accountServerId + " active is " + a.active) } var contactList = allDao.getAllContacts() for (c: Contact in contactList) { Log.d("CONTACTINFO","Contact ID is " + c.contactId + " Contact Name is " + c.contactName + " Contact Server ID is " + c.contactServerId) } val csaList = allDao.getContactServerAccount(true) for (c: ContactServerAccount in csaList) { Log.d( "CSAINFO", "SERVER ID is " + c.serverAccount!!.server!!.serverId + " ACCOUNT ID is " + c.serverAccount!!.account!!.accountId + " CONTACT ID is " + c.contact.contactId + " CONTACT NAME is " + c.contact.contactName ) } val csalList = allDao.getContactServerAccountLimited(true) for (c: ContactServerAccountLimited in csalList) { Log.d( "CSALINFO", "SERVER ID is " + c.serverId + " ACCOUNT ID is " + c.accountId + " CONTACT ID is " + c.contact.contactId + " CONTACT NAME is " + c.contact.contactName ) } }
然后输出将是:-
2019-10-29 20:56:59.942 D/SERVERINFO: Server ID is 1 Name is Server 1
2019-10-29 20:56:59.943 D/SERVERINFO: Server ID is 2 Name is Server 2
2019-10-29 20:56:59.943 D/SERVERINFO: Server ID is 3 Name is Server 3
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 1 Account Name is FRED Account Server ID is 1 active is true
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 2 Account Name is MARY Account Server ID is 1 active is false
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 3 Account Name is JANE Account Server ID is 2 active is false
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 4 Account Name is ANNE Account Server ID is 2 active is false
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 5 Account Name is VERA Account Server ID is 3 active is false
2019-10-29 20:56:59.945 D/ACCOUNTINFO: Account ID is 6 Account Name is JOHN Account Server ID is 3 active is false
2019-10-29 20:56:59.947 D/CONTACTINFO: Contact ID is 1 Contact Name is C1 Contact Server ID is 1
2019-10-29 20:56:59.947 D/CONTACTINFO: Contact ID is 2 Contact Name is C2 Contact Server ID is 2
2019-10-29 20:56:59.947 D/CONTACTINFO: Contact ID is 3 Contact Name is C3 Contact Server ID is 3
2019-10-29 20:56:59.947 D/CONTACTINFO: Contact ID is 4 Contact Name is C4 Contact Server ID is 3
2019-10-29 20:56:59.953 D/CSAINFO: SERVER ID is 1 ACCOUNT ID is 2 CONTACT ID is 1 CONTACT NAME is C1
2019-10-29 20:56:59.954 D/CSALINFO: SERVER ID is 1 ACCOUNT ID is 1 CONTACT ID is 1 CONTACT NAME is C1