code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.skywalking.oap.server.core.analysis.metrics.annotation;
  
  import java.lang.annotation.ElementType;
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.lang.annotation.Target;
  import org.apache.skywalking.oap.server.core.analysis.metrics.expression.BooleanMatch;
  
  /**
   * Classes annotated with {@code FilterMatcher} are processors of the expressions in {@code filter} of the OAL script.
   * Take {@link BooleanMatch} as an example.
   */
  @Target(ElementType.TYPE)
  @Retention(RetentionPolicy.RUNTIME)
  public @interface FilterMatcher {
      /**
       * @return the operator name(s) defined in the .g4 files, such as {@code lessEqualMatch} and {@code notEqualMatch},
       * the default value is the name of the class annotated with {@link FilterMatcher}, with the first letter being
       * lowercase.
       */
      String[] value() default {};
  }
  