@Column @Basic

 @Basic

@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface Basic {

    /**
     * (Optional) Defines whether the value of the field or property should
     * be lazily loaded or must be eagerly fetched. The <code>EAGER</code>
     * strategy is a requirement on the persistence provider runtime
     * that the value must be eagerly fetched.  The <code>LAZY</code>
     * strategy is a hint to the persistence provider runtime.
     * If not specified, defaults to <code>EAGER</code>.
     */
    FetchType fetch() default EAGER;

    /**
     * (Optional) Defines whether the value of the field or property may be null.
     * This is a hint and is disregarded for primitive types; it may
     * be used in schema generation.
     * If not specified, defaults to <code>true</code>.
     */
    boolean optional() default true;
}

是否懒加载，是否为空

@Column

/*
 * 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.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 <code>Column</code> annotation is specified, the default values apply.
 *
 * <blockquote><pre>
 *    Example 1:
 *
 *    &#064;Column(name="DESC", nullable=false, length=512)
 *    public String getDescription() { return description; }
 *
 *    Example 2:
 *
 *    &#064;Column(name="DESC",
 *            columnDefinition="CLOB NOT NULL",
 *            table="EMP_DETAIL")
 *    &#064;Lob
 *    public String getDescription() { return description; }
 *
 *    Example 3:
 *
 *    &#064;Column(name="ORDER_COST", updatable=false, precision=12, scale=2)
 *    public BigDecimal getCost() { return cost; }
 *
 * </pre></blockquote>
 *
 *
 * @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 <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.
     */
    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.
     * <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.
     */
    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;
}

可以设置列名、是否可以为null、插入时是否用此字段、更新时是否用此字段，字符的长度，数字的总长度，小数点所占位数等。