src/javax/persistence/IdClass.java

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package javax.persistence;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Specifies a composite primary key class that is mapped to 
 * multiple fields or properties of the entity.  
 *
 * <p> The names of the fields or properties in the primary key 
 * class and the primary key fields or properties of the entity 
 * must correspond and their types must be the same.
 *
 * <pre>
 *
 *   Example:
 *
 *   &#064;IdClass(com.acme.EmployeePK.class)
 *   &#064;Entity
 *   public class Employee {
 *     &#064;Id String empName;
 *     &#064;Id Date birthDay;
 *     ...
 *   }
 * </pre>
 *
 * @since Java Persistence 1.0
 */
@Target({TYPE})
@Retention(RUNTIME)

public @interface IdClass {

    /** Primary key class */
    Class value();
}