OrmContext

所有超级接口:

AutoCloseable
```
public interface OrmContext
extends AutoCloseable
```
An interface provided by the object relational mapping (ORM) system for operating ORM database entities defined in OrmObject.
Applications can use this interface to create, retrieve, update, and delete database entities.

从以下版本开始:

1

另请参阅:

OrmObject

SystemCapability

SystemCapability.Data#DATA_APPDATAMGR

方法概要

所有方法实例方法抽象方法
限定符和类型	方法	说明
`Double`	`avg(OrmPredicates predicates, String field)`	Queries data that meets the conditions specified in the `OrmPredicates` instance and returns the average value of the matched data in a specified column.
`boolean`	`backup(String destPath)`	Backs up the current database to a specified path.
`boolean`	`backup(String destPath, byte[] destEncryptKey)`	Backs up a database in a specified path using a specified encryption key.
`void`	`beginTransaction()`	Begins a transaction in EXCLUSIVE mode.
`void`	`changeEncryptKey(byte[] newEncryptKey)`	Changes the encryption key of an encrypted object-relational mapping (ORM) database that is opened.
`void`	`close()`	Clears the memory data and releases the store.
`void`	`commit()`	Commits a transaction.
`Long`	`count(OrmPredicates predicates)`	Queries data that meets the conditions specified by the `OrmPredicates` instance and returns the number of the matched data records in a specified column.
`int`	`delete(OrmPredicates predicates)`	Deletes `OrmObject` instances that meet the conditions specified by the `OrmPredicates` instance.
`<T extends OrmObject> boolean`	`delete(T object)`	Deletes an object from the database.
`boolean`	`flush()`	Writes unsaved data changes into the database.
`String`	`getAlias()`	Obtains the storage alias related to the current database context.
`<T extends OrmObject> boolean`	`insert(T object)`	Inserts an object to the database.
`boolean`	`isInTransaction()`	Specifies whether the object is in a transaction.
`Double`	`max(OrmPredicates predicates, String field)`	Queries data that meets the conditions specified by the `OrmPredicates` instance and returns the maximum value of the matched data in a specified column.
`Double`	`min(OrmPredicates predicates, String field)`	Queries data that meets the conditions specified in the `OrmPredicates` instance and returns the minimum value of the matched data in a specified column.
`<T extends OrmObject> List<T>`	`query(OrmPredicates predicates)`	Queries `OrmObject` instances that meet the conditions specified by the `OrmPredicates` instance.
`ResultSet`	`query(OrmPredicates predicates, String[] columns)`	Queries results that meet the conditions specified by the `OrmPredicates` instance and returns the results based on specified columns.
`void`	`registerContextObserver(OrmContext watchedContext, OrmObjectObserver observer)`	Registers an `OrmObjectObserver` object to listen for changes of a specified `OrmContext` object.
`void`	`registerEntityObserver(String entityName, OrmObjectObserver observer)`	Registers an `OrmObjectObserver` object to listen for changes of a specified `Entity` object.
`void`	`registerObjectObserver(OrmObject ormObject, OrmObjectObserver observer)`	Registers an `OrmObjectObserver` object to listen for changes of a specified `OrmObject` instance.
`void`	`registerStoreObserver(String alias, OrmObjectObserver observer)`	Registers an `OrmObjectObserver` object to listen for changes in the storage specified by its alias.
`boolean`	`restore(String srcPath)`	Restores data from a specified database file.
`boolean`	`restore(String srcPath, byte[] srcEncryptKey, byte[] destEncryptKey)`	Restores a database from a specified encrypted or unencrypted database file.
`void`	`rollback()`	Rolls back a transaction.
`Double`	`sum(OrmPredicates predicates, String field)`	Queries data that meets the conditions specified in the `OrmPredicates` instance and returns the sum of the matched data in a specified column.
`void`	`unregisterContextObserver(OrmContext watchedContext, OrmObjectObserver observer)`	Unregisters the `OrmObjectObserver` object used to listen for changes of a specified `OrmContext` object.
`void`	`unregisterEntityObserver(String entityName, OrmObjectObserver observer)`	Unregisters the `OrmObjectObserver` object used to listen for changes of a specified `Entity` object.
`void`	`unregisterObjectObserver(OrmObject ormObject, OrmObjectObserver observer)`	Unregisters the `OrmObjectObserver` object used to listen for changes of a specified `OrmObject` instance.
`void`	`unregisterStoreObserver(String alias, OrmObjectObserver observer)`	Unregisters the `OrmObjectObserver` object used to listen for changes in the storage specified by its alias.
`int`	`update(OrmPredicates predicates, ValuesBucket value)`	Updates information in `ValuesBucket` to a specified `OrmObject` instance based on the conditions specified by the `OrmPredicates` instance.
`<T extends OrmObject> boolean`	`update(T object)`	Updates an object in the database.
`<T extends OrmObject> OrmPredicates`	`where(Class<T> clz)`	Creates an `OrmPredicates` instance.

- 方法详细资料
  - insert
```
<T extends OrmObject> boolean insert(T object)
```
    Inserts an object to the database.
    After this method is executed, data changes are stored in the memory. You need to use OrmContext#flush to save the data changes in a database file.
    
    类型参数:
    
    T - Indicates the object type, which is restricted to subclasses of OrmObject.
    
    参数:
    
    object - Indicates the object to be inserted.
    
    返回:
    
    Returns true if the object is inserted; returns false otherwise.
    
    从以下版本开始:
    
    1
  - update
```
<T extends OrmObject> boolean update(T object)
```
    Updates an object in the database.
    After this method is executed, data changes are stored in the memory. You need to use OrmContext#flush to save the data changes in a database file.
    
    类型参数:
    
    T - Restricts the results that belong to the specified OrmObject.
    
    参数:
    
    object - Indicates the object to be updated.
    
    返回:
    
    Returns true if the operation is successful; returns false otherwise.
    
    从以下版本开始:
    
    1
  - delete
```
<T extends OrmObject> boolean delete(T object)
```
    Deletes an object from the database.
    After this method is executed, data changes are stored in the memory. You need to use OrmContext#flush to save the data changes in a database file.
    
    类型参数:
    
    T - Restricts the results that belong to the specified OrmObject.
    
    参数:
    
    object - Indicates the object to be deleted.
    
    返回:
    
    Returns true if the operation is successful; returns false otherwise.
    
    从以下版本开始:
    
    1
  - where
```
<T extends OrmObject> OrmPredicates where(Class<T> clz)
```
    Creates an OrmPredicates instance.
    You can use this method to restrict the class of objects to be operated. To perform more specific database operations, use OrmPredicates.
    
    类型参数:
    
    T - Indicates the type of clz, which is restricted to subclasses of OrmObject.
    
    参数:
    
    clz - Indicates the class of the objects to search.
    
    返回:
    
    Returns the created OrmPredicates instance.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - query
```
<T extends OrmObject> List<T> query(OrmPredicates predicates)
```
    Queries OrmObject instances that meet the conditions specified by the OrmPredicates instance.
    You can use OrmPredicates to limit the operation range. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    类型参数:
    
    T - Indicates the type of elements in the returned list, which is restricted to subclasses of OrmObject.
    
    参数:
    
    predicates - Indicates the predicates that contain the match conditions.
    
    返回:
    
    Returns the list of the queried instances; returns an empty list if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - query
```
ResultSet query(OrmPredicates predicates,
                String[] columns)
```
    Queries results that meet the conditions specified by the OrmPredicates instance and returns the results based on specified columns.
    This method supports cross-process query.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    columns - Indicates the database column names.
    
    返回:
    
    Returns the result set; returns an empty ResultSet instance if no data is matched.
    
    从以下版本开始:
    
    1
  - delete
```
int delete(OrmPredicates predicates)
```
    Deletes OrmObject instances that meet the conditions specified by the OrmPredicates instance.
    You can use OrmPredicates to limit the operation range. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    返回:
    
    Returns the number of objects deleted; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - update
```
int update(OrmPredicates predicates,
           ValuesBucket value)
```
    Updates information in ValuesBucket to a specified OrmObject instance based on the conditions specified by the OrmPredicates instance.
    You can use OrmPredicates to limit the operation range. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    value - Indicates the map that caches a row of data. The keys should be the column names and the mapping values.
    
    返回:
    
    Returns the number of objects updated; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - count
```
Long count(OrmPredicates predicates)
```
    Queries data that meets the conditions specified by the OrmPredicates instance and returns the number of the matched data records in a specified column.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    返回:
    
    Returns the number of matched data records; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - max
```
Double max(OrmPredicates predicates,
           String field)
```
    Queries data that meets the conditions specified by the OrmPredicates instance and returns the maximum value of the matched data in a specified column.
    If no data meets the conditions, this method will return 0. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    field - Indicates the column name.
    
    返回:
    
    Returns the maximum value of the matched data in the specified column; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - min
```
Double min(OrmPredicates predicates,
           String field)
```
    Queries data that meets the conditions specified in the OrmPredicates instance and returns the minimum value of the matched data in a specified column.
    If no data meets the conditions, this method will return 0. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates predicates that contain the match conditions.
    
    field - Indicates the column name.
    
    返回:
    
    Returns the minimum value of the matched data in the specified column; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - avg
```
Double avg(OrmPredicates predicates,
           String field)
```
    Queries data that meets the conditions specified in the OrmPredicates instance and returns the average value of the matched data in a specified column.
    If no data meets the conditions, this method will return 0. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates the predicates that contain the match conditions.
    
    field - Indicates the column name.
    
    返回:
    
    Returns the average value of the matched data in the specified column; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - sum
```
Double sum(OrmPredicates predicates,
           String field)
```
    Queries data that meets the conditions specified in the OrmPredicates instance and returns the sum of the matched data in a specified column.
    If no data meets the conditions, this method will return 0. Conditions contained in the OrmPredicates instance must be compliant with SQL statement logic.
    
    参数:
    
    predicates - Indicates the predicates that contain the {code sum} conditions.
    
    field - Indicates the column name.
    
    返回:
    
    Returns the sum of matched data in the specified column; returns 0 if no data is matched.
    
    从以下版本开始:
    
    1
    
    另请参阅:
    
    OrmPredicates
  - flush
```
boolean flush()
```
    Writes unsaved data changes into the database.
    This method is generally used after OrmContext#insert, OrmContext#update, and OrmContext#delete to write memory data into a database file.
    
    返回:
    
    Returns true if the memory data is written into the database; returns false otherwise.
    
    从以下版本开始:
    
    1
  - beginTransaction
```
void beginTransaction()
```
    Begins a transaction in EXCLUSIVE mode.
    Here is the standard idiom for transactions: ormContext.beginTransaction(); try { ... ormContext.commit(); } catch (RdbException e) { ormContext.rollback(); }
    
    从以下版本开始:
    
    1
  - commit
```
void commit()
```
    Commits a transaction.
    See beginTransaction() for notes about how to use this and when transactions are committed and rolled back.
    
    从以下版本开始:
    
    1
  - isInTransaction
```
boolean isInTransaction()
```
    Specifies whether the object is in a transaction.
    
    返回:
    
    Returns true if the object is in a transaction; returns false otherwise.
    
    从以下版本开始:
    
    1
  - rollback
```
void rollback()
```
    Rolls back a transaction.
    See beginTransaction() for notes about how to use this and when transactions are committed and rolled back.
    
    从以下版本开始:
    
    1
  - getAlias
```
String getAlias()
```
    Obtains the storage alias related to the current database context.
    
    返回:
    
    Returns the storage alias.
    
    从以下版本开始:
    
    1
  - changeEncryptKey
```
void changeEncryptKey(byte[] newEncryptKey)
```
    Changes the encryption key of an encrypted object-relational mapping (ORM) database that is opened.
    This method applies only to an encrypted ORM database and cannot be used to change it to an unencrypted one. Before calling this method, ensure that the database is opened and that no transaction is using the database connection. For the maximum size of the encryption key, see OrmConfig#MAX_ENCRYPT_KEY_SIZE.
    
    参数:
    
    newEncryptKey - Indicates the new encryption key of the ORM database.
    
    抛出:
    
    IllegalArgumentException - Throws this exception if the new encryption key is null or an empty string.
    
    IllegalStateException - Throws this exception if the database is not opened or not encrypted, or a transaction is using the database connection.
    
    RdbException - Throws this exception if changing the encryption key of the encrypted ORM database fails.
    
    从以下版本开始:
    
    3
  - close
```
void close()
```
    Clears the memory data and releases the store. A context is no longer available after being closed.
    
    指定者:
    
    close 在接口中 AutoCloseable
    
    从以下版本开始:
    
    1
  - backup
```
boolean backup(String destPath)
```
    Backs up the current database to a specified path.
    
    参数:
    
    destPath - Indicates the path for backing up the database.
    
    返回:
    
    Returns true if the database backup is successful; returns false otherwise.
    
    从以下版本开始:
    
    1
  - restore
```
boolean restore(String srcPath)
```
    Restores data from a specified database file.
    
    参数:
    
    srcPath - Indicates the path where the database file is stored.
    
    返回:
    
    Returns true if the data is restored successfully; returns false otherwise.
    
    从以下版本开始:
    
    1
  - backup
```
boolean backup(String destPath,
               byte[] destEncryptKey)
```
    Backs up a database in a specified path using a specified encryption key.
    The generated backup is encrypted. If destEncryptKey is null, the generated backup is unencrypted. In that case, this method is equivalent to the OrmContext#backup(String) method. For the maximum size of the encryption key, see OrmConfig#MAX_ENCRYPT_KEY_SIZE.
    
    参数:
    
    destPath - Indicates the path that saves the database backup. Ensure that your application has write permissions to this path.
    
    destEncryptKey - Indicates the encryption key of the database to back up. It can be different from that of the current database.
    
    返回:
    
    Returns true if the database is backed up successfully; returns false otherwise.
    
    从以下版本开始:
    
    3
  - restore
```
boolean restore(String srcPath,
                byte[] srcEncryptKey,
                byte[] destEncryptKey)
```
    Restores a database from a specified encrypted or unencrypted database file.
    When being called, this method deletes the original data and generates an encrypted or unencrypted database, as defined by your application. If both srcEncryptKey and destEncryptKey are null, this method is equivalent to the OrmContext#restore(String) method. For the maximum size of the encryption key, see OrmConfig#MAX_ENCRYPT_KEY_SIZE.
    
    参数:
    
    srcPath - Indicates the path that stores the source database file. Ensure that your application has write permissions to this path.
    
    srcEncryptKey - Indicates the encryption key of the source database. If the database is unencrypted, set the value of this parameter to null.
    
    destEncryptKey - Indicates the encryption key of the restored database.If you want the database to be unencrypted, set the value of this parameter to null.
    
    返回:
    
    Returns true if the database is restored successfully; returns false otherwise.
    
    从以下版本开始:
    
    3
  - registerStoreObserver
```
void registerStoreObserver(String alias,
                           OrmObjectObserver observer)
```
    Registers an OrmObjectObserver object to listen for changes in the storage specified by its alias.
    
    参数:
    
    alias - Indicates the alias of the storage to be listened.
    
    observer - Indicates the storage observer.
    
    从以下版本开始:
    
    1
  - registerContextObserver
```
void registerContextObserver(OrmContext watchedContext,
                             OrmObjectObserver observer)
```
    Registers an OrmObjectObserver object to listen for changes of a specified OrmContext object.
    
    参数:
    
    watchedContext - Indicates the OrmContext object to be listened.
    
    observer - Indicates the observer of the OrmContext object.
    
    从以下版本开始:
    
    1
  - registerEntityObserver
```
void registerEntityObserver(String entityName,
                            OrmObjectObserver observer)
```
    Registers an OrmObjectObserver object to listen for changes of a specified Entity object.
    
    参数:
    
    entityName - Indicates the name of the database entity to be listened.
    
    observer - Indicates the observer of the Entity object.
    
    从以下版本开始:
    
    1
  - registerObjectObserver
```
void registerObjectObserver(OrmObject ormObject,
                            OrmObjectObserver observer)
```
    Registers an OrmObjectObserver object to listen for changes of a specified OrmObject instance.
    
    参数:
    
    ormObject - Indicates the OrmObject instance to be listened.
    
    observer - Indicates the observer of the OrmObject instance.
    
    从以下版本开始:
    
    1
  - unregisterStoreObserver
```
void unregisterStoreObserver(String alias,
                             OrmObjectObserver observer)
```
    Unregisters the OrmObjectObserver object used to listen for changes in the storage specified by its alias.
    
    参数:
    
    alias - Indicates the alias of the storage being listened.
    
    observer - Indicates the OrmObjectObserver object to unregister.
    
    从以下版本开始:
    
    1
  - unregisterContextObserver
```
void unregisterContextObserver(OrmContext watchedContext,
                               OrmObjectObserver observer)
```
    Unregisters the OrmObjectObserver object used to listen for changes of a specified OrmContext object.
    
    参数:
    
    watchedContext - Indicates the OrmContext object being listened.
    
    observer - Indicates the OrmObjectObserver object to unregister.
    
    从以下版本开始:
    
    1
  - unregisterEntityObserver
```
void unregisterEntityObserver(String entityName,
                              OrmObjectObserver observer)
```
    Unregisters the OrmObjectObserver object used to listen for changes of a specified Entity object.
    
    参数:
    
    entityName - Indicates the name of the database entity being listened.
    
    observer - Indicates the OrmObjectObserver object to unregister.
    
    从以下版本开始:
    
    1
  - unregisterObjectObserver
```
void unregisterObjectObserver(OrmObject ormObject,
                              OrmObjectObserver observer)
```
    Unregisters the OrmObjectObserver object used to listen for changes of a specified OrmObject instance.
    
    参数:
    
    ormObject - Indicates the OrmObject instance that has been listened.
    
    observer - Indicates the OrmObjectObserver object to unregister.
    
    从以下版本开始:
    
    1

接口 OrmContext

方法概要

方法详细资料

insert

update

delete

where

query

query

delete

update

count

max

min

avg

sum

flush

beginTransaction

commit

isInTransaction

rollback

getAlias

changeEncryptKey

close

backup

restore

backup

restore

registerStoreObserver

registerContextObserver

registerEntityObserver

registerObjectObserver

unregisterStoreObserver

unregisterContextObserver

unregisterEntityObserver

unregisterObjectObserver