net.java.ao.ValueGenerator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of activeobjects Show documentation

This is the full Active Objects library, if you don't know which one to use, you probably want this one.

The newest version!

/*
 * Copyright 2007 Daniel Spiewak
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at
 * 
 *	    http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.java.ao;

/**
 * A super-interface designed to allow auto-generated values
 * to be inserted into database fields on INSERT.  Potentially,
 * this could be expanded to also include on UPDATE
 * functionality, but for the moment it only handles on entity
 * creation (INSERT).  Implementations are assumed to be
 * completely stateless and thus thread-safe.
 *
 * The type parameter represents the return type of the
 * method which does the actual generation.
 *
 * @author Daniel Spiewak
 * @see net.java.ao.Generator
 */
public interface ValueGenerator {

    /**
     * Generate a new value for an arbitrary field.  No write
     * database operations should be performed within this
     * method.  The EntityManager instance is only
     * intended to ensure various field constraints (such as
     * uniqueness for primary keys).  Great care should be
     * taken with performing such operations, as the value
     * generation method needs to be extremely efficient.
     *
     * @param manager An instance to gain read access to the database.
     * @return A new value of the relevant type for INSERT.
     */
    public T generateValue(EntityManager manager);
}