UserType (Hibernate API Documentation) - Hibernate 3.2.3 正式版 API 英文文档

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org.hibernate.usertype
Interface UserType

All Known Subinterfaces:: EnhancedUserType, UserVersionType

public interface UserType

This interface should be implemented by user-defined "types". A "type" class is not the actual property type - it is a class that knows how to serialize instances of another class to and from JDBC.

This interface

abstracts user code from future changes to the Type interface,
simplifies the implementation of custom types and
hides certain "internal" interfaces from user code.

Implementors must be immutable and must declare a public default constructor.

The actual class mapped by a UserType may be just about anything.

CompositeUserType provides an extended version of this interface that is useful for more complex cases.

Alternatively, custom types could implement Type directly or extend one of the abstract classes in org.hibernate.type. This approach risks future incompatible changes to classes or interfaces in that package.

Author:: Gavin King
See Also:: for more complex cases, Type

Method Summary

Object assemble(Serializable cached, Object owner)
          Reconstruct an object from the cacheable representation.

Object deepCopy(Object value)
          Return a deep copy of the persistent state, stopping at entities and at collections.

Serializable disassemble(Object value)
          Transform the object into its cacheable representation.

boolean equals(Object x, Object y)
          Compare two instances of the class mapped by this type for persistence "equality".

int hashCode(Object x)
          Get a hashcode for the instance, consistent with persistence "equality"

boolean isMutable()
          Are objects of this type mutable?

Object nullSafeGet(ResultSet rs, String[] names, Object owner)
          Retrieve an instance of the mapped class from a JDBC resultset.

void nullSafeSet(PreparedStatement st, Object value, int index)
          Write an instance of the mapped class to a prepared statement.

Object replace(Object original, Object target, Object owner)
          During merge, replace the existing (target) value in the entity we are merging to with a new (original) value from the detached entity we are merging.

Class returnedClass()
          The class returned by nullSafeGet().

int[] sqlTypes()
          Return the SQL type codes for the columns mapped by this type.

Method Detail

sqlTypes

public int[] sqlTypes()

Return the SQL type codes for the columns mapped by this type. The codes are defined on java.sql.Types.

Returns:: int[] the typecodes
See Also:: Types

returnedClass

public Class returnedClass()

The class returned by nullSafeGet().

Returns:: Class

equals

public boolean equals(Object x,
                      Object y)
               throws HibernateException

Compare two instances of the class mapped by this type for persistence "equality". Equality of the persistent state.

Parameters:: x -; y -
Returns:: boolean
Throws:: HibernateException

hashCode

public int hashCode(Object x)
             throws HibernateException

Get a hashcode for the instance, consistent with persistence "equality"

Throws:: HibernateException

nullSafeGet

public Object nullSafeGet(ResultSet rs,
                          String[] names,
                          Object owner)
                   throws HibernateException,
                          SQLException

Retrieve an instance of the mapped class from a JDBC resultset. Implementors should handle possibility of null values.

Parameters:: rs - a JDBC result set; names - the column names; owner - the containing entity
Returns:: Object
Throws:: HibernateException; SQLException

nullSafeSet

public void nullSafeSet(PreparedStatement st,
                        Object value,
                        int index)
                 throws HibernateException,
                        SQLException

Write an instance of the mapped class to a prepared statement. Implementors should handle possibility of null values. A multi-column type should be written to parameters starting from index.

Parameters:: st - a JDBC prepared statement; value - the object to write; index - statement parameter index
Throws:: HibernateException; SQLException

deepCopy

public Object deepCopy(Object value)
                throws HibernateException

Return a deep copy of the persistent state, stopping at entities and at collections. It is not necessary to copy immutable objects, or null values, in which case it is safe to simply return the argument.

Parameters:: value - the object to be cloned, which may be null
Returns:: Object a copy
Throws:: HibernateException

isMutable

public boolean isMutable()

Are objects of this type mutable?

Returns:: boolean

disassemble

public Serializable disassemble(Object value)
                         throws HibernateException

Transform the object into its cacheable representation. At the very least this method should perform a deep copy if the type is mutable. That may not be enough for some implementations, however; for example, associations must be cached as identifier values. (optional operation)

Parameters:: value - the object to be cached
Returns:: a cachable representation of the object
Throws:: HibernateException

assemble

public Object assemble(Serializable cached,
                       Object owner)
                throws HibernateException

Reconstruct an object from the cacheable representation. At the very least this method should perform a deep copy if the type is mutable. (optional operation)

Parameters:: cached - the object to be cached; owner - the owner of the cached object
Returns:: a reconstructed object from the cachable representation
Throws:: HibernateException

replace

public Object replace(Object original,
                      Object target,
                      Object owner)
               throws HibernateException

During merge, replace the existing (target) value in the entity we are merging to with a new (original) value from the detached entity we are merging. For immutable objects, or null values, it is safe to simply return the first parameter. For mutable objects, it is safe to return a copy of the first parameter. For objects with component values, it might make sense to recursively replace component values.

Parameters:: original - the value from the detached entity being merged; target - the value in the managed entity
Returns:: the value to be merged
Throws:: HibernateException