org.apache.ibatis.annotations.SelectProvider.java Source code

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/**
 *    Copyright 2009-2019 the original author or authors.
 *
 *    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 org.apache.ibatis.annotations;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * The annotation that specify a method that provide an SQL for retrieving record(s).
 *
 * <p><br>
 * <b>How to use:</b>
 * <pre>
 * public interface UserMapper {
 *
 *   &#064;SelectProvider(type = SqlProvider.class, method = "selectById")
 *   User selectById(int id);
 *
 *   public static class SqlProvider {
 *     public static String selectById() {
 *       return "SELECT id, name FROM users WHERE id = #{id}";
 *     }
 *   }
 *
 * }
 * </pre>
 * @author Clinton Begin
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface SelectProvider {

    /**
     * Specify a type that implements an SQL provider method.
     *
     * @return a type that implements an SQL provider method
     * @since 3.5.2
     * @see #type()
     */
    Class<?> value() default void.class;

    /**
     * Specify a type that implements an SQL provider method.
     * <p>
     * This attribute is alias of {@link #value()}.
     * </p>
     *
     * @return a type that implements an SQL provider method
     * @see #value()
     */
    Class<?> type() default void.class;

    /**
     * Specify a method for providing an SQL.
     *
     * <p>
     * Since 3.5.1, this attribute can omit.
     * If this attribute omit, the MyBatis will call a method that decide by following rules.
     * <ul>
     *   <li>
     *     If class that specified the {@link #type()} attribute implements the {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver},
     *     the MyBatis use a method that returned by it
     *   </li>
     *   <li>
     *     If cannot resolve a method by {@link org.apache.ibatis.builder.annotation.ProviderMethodResolver}(= not implement it or it was returned {@code null}),
     *     the MyBatis will search and use a fallback method that named {@code provideSql} from specified type
     *   </li>
     * </ul>
     *
     * @return a method name of method for providing an SQL
     */
    String method() default "";

}