/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.  The Eclipse Public License is available
 * at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
 * is available at http://www.eclipse.org/org/documents/edl-v10.php.
 */
package javax.persistence;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

Is used to specify the mapped column for a persistent property or field.
If no Column annotation is specified, the default values apply.

   Example 1:

   @Column(name="DESC", nullable=false, length=512)
   public String getDescription() { return description; }

   Example 2:

   @Column(name="DESC",
           columnDefinition="CLOB NOT NULL",
           table="EMP_DETAIL")
   @Lob
   public String getDescription() { return description; }

   Example 3:

   @Column(name="ORDER_COST", updatable=false, precision=12, scale=2)
   public BigDecimal getCost() { return cost; }


Since:
Java Persistence 1.0/**
 * Is used to specify the mapped column for a persistent property or field.
 * If no <code>Column</code> annotation is specified, the default values apply.
 * <p>
 * <blockquote><pre>
 *    Example 1:
 * <p>
 *    &#064;Column(name="DESC", nullable=false, length=512)
 *    public String getDescription() { return description; }
 * <p>
 *    Example 2:
 * <p>
 *    &#064;Column(name="DESC",
 *            columnDefinition="CLOB NOT NULL",
 *            table="EMP_DETAIL")
 *    &#064;Lob
 *    public String getDescription() { return description; }
 * <p>
 *    Example 3:
 * <p>
 *    &#064;Column(name="ORDER_COST", updatable=false, precision=12, scale=2)
 *    public BigDecimal getCost() { return cost; }
 * <p>
 * </pre></blockquote>
 *
 * @since Java Persistence 1.0
 */
@Target({METHOD, FIELD, ANNOTATION_TYPE})
@Retention(RUNTIME)
public @interface Column {

  
(Optional) The name of the column. Defaults to
the property or field name.
/**
   * (Optional) The name of the column. Defaults to
   * the property or field name.
   */
  String name() default "";

  
(Optional) Whether the column is a unique key.  This is a
shortcut for the UniqueConstraint annotation at the table
level and is useful for when the unique key constraint
corresponds to only a single column. This constraint applies
in addition to any constraint entailed by primary key mapping and
to constraints specified at the table level.
/**
   * (Optional) Whether the column is a unique key.  This is a
   * shortcut for the <code>UniqueConstraint</code> annotation at the table
   * level and is useful for when the unique key constraint
   * corresponds to only a single column. This constraint applies
   * in addition to any constraint entailed by primary key mapping and
   * to constraints specified at the table level.
   */
  boolean unique() default false;

  
(Optional) Whether the database column is nullable.
/**
   * (Optional) Whether the database column is nullable.
   */
  boolean nullable() default true;

  
(Optional) Whether the column is included in SQL INSERT
statements generated by the persistence provider.
/**
   * (Optional) Whether the column is included in SQL INSERT
   * statements generated by the persistence provider.
   */
  boolean insertable() default true;

  
(Optional) Whether the column is included in SQL UPDATE
statements generated by the persistence provider.
/**
   * (Optional) Whether the column is included in SQL UPDATE
   * statements generated by the persistence provider.
   */
  boolean updatable() default true;

  
(Optional) The SQL fragment that is used when
generating the DDL for the column.
 Defaults to the generated SQL to create a
column of the inferred type.
/**
   * (Optional) The SQL fragment that is used when
   * generating the DDL for the column.
   * <p> Defaults to the generated SQL to create a
   * column of the inferred type.
   */
  String columnDefinition() default "";

  
(Optional) The name of the table that contains the column.
If absent the column is assumed to be in the primary table.
/**
   * (Optional) The name of the table that contains the column.
   * If absent the column is assumed to be in the primary table.
   */
  String table() default "";

  
(Optional) The column length. (Applies only if a
string-valued column is used.)
/**
   * (Optional) The column length. (Applies only if a
   * string-valued column is used.)
   */
  int length() default 255;

  
(Optional) The precision for a decimal (exact numeric)
column. (Applies only if a decimal column is used.)
Value must be set by developer if used when generating
the DDL for the column.
/**
   * (Optional) The precision for a decimal (exact numeric)
   * column. (Applies only if a decimal column is used.)
   * Value must be set by developer if used when generating
   * the DDL for the column.
   */
  int precision() default 0;

  
(Optional) The scale for a decimal (exact numeric) column.
(Applies only if a decimal column is used.)
/**
   * (Optional) The scale for a decimal (exact numeric) column.
   * (Applies only if a decimal column is used.)
   */
  int scale() default 0;
}