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Hibernate definition of the Java Persistence 2.0 (JSR 317) API.
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// $Id: Column.java 17752 2009-10-15 01:19:21Z [email protected] $
// EJB3 Specification Copyright 2004-2009 Sun Microsystems, Inc.
package javax.persistence;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.FIELD;
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
 */
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface Column {

    /**
     * (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.
     */
    boolean unique() default false;

    /**
     * (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.
     */
    boolean insertable() default true;

    /**
     * (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.
     */
    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.
     */
    String table() default "";

    /**
     * (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.
     */
    int precision() default 0;

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