log4j-plugins/src/main/java/org/apache/logging/log4j/plugins/PluginAttribute.java

/*
 * 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.logging.log4j.plugins;

import org.apache.logging.log4j.plugins.inject.InjectorStrategy;
import org.apache.logging.log4j.plugins.inject.PluginAttributeInjector;
import org.apache.logging.log4j.plugins.name.NameProvider;
import org.apache.logging.log4j.plugins.name.PluginAttributeNameProvider;
import org.apache.logging.log4j.util.Strings;

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;

/**
 * Identifies a Plugin Attribute along with optional metadata. Plugin attributes can be injected as parameters to
 * a static {@linkplain PluginFactory factory method}, or as fields and single-parameter methods in a plugin
 * {@linkplain org.apache.logging.log4j.plugins.util.Builder builder class}.
 *
 * <p>Default values may be specified via one of the <code>default<var>Type</var></code> attributes depending on the
 * annotated type. Unlisted types that are supported by a corresponding
 * {@link org.apache.logging.log4j.plugins.convert.TypeConverter} may use the {@link #defaultString()} attribute.
 * When annotating a field, a default value can be specified by the field's initial value instead of using one of the
 * annotation attributes.</p>
 *
 * <p>Plugin attributes with sensitive data such as passwords should specify {@link #sensitive()} to avoid having
 * their values logged in debug logs.</p>
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.PARAMETER, ElementType.FIELD, ElementType.METHOD})
@InjectorStrategy(PluginAttributeInjector.class)
@NameProvider(PluginAttributeNameProvider.class)
public @interface PluginAttribute {

    /**
     * Specifies the default boolean value to use.
     * @return the default boolean value.
     */
    boolean defaultBoolean() default false;

    /**
     * Specifies the default byte value to use.
     * @return the default byte value;
     */
    byte defaultByte() default 0;

    /**
     * Specifies the default byte value to use.
     * @return the default char value.
     */
    char defaultChar() default 0;

    /**
     * Specifies the default {@link Class} value to use.
     * @return the default class value.
     */
    Class<?> defaultClass() default Object.class;

    /**
     * Specifies the default double floating point value to use.
     * @return the default double value;
     */
    double defaultDouble() default 0.0d;

    /**
     * Specifies the default floating point value to use.
     * @return the default float value.
     */
    float defaultFloat() default 0.0f;

    /**
     * Specifies the default integer value to use.
     * @return the default integer value.
     */
    int defaultInt() default 0;

    /**
     * Specifies the default long value to use.
     * @return the default long value;
     */
    long defaultLong() default 0L;

    /**
     * Specifies the default long value to use.
     * @return the default short value.
     */
    short defaultShort() default 0;

    /**
     * Specifies the default value this attribute should use if none is provided or if the provided value is invalid.
     * @return the default String value.
     */
    String defaultString() default Strings.EMPTY;

    /**
     * Specifies the name of the attribute (case-insensitive) this annotation corresponds to.
     * If blank, defaults to using reflection on the annotated element as such:
     *
     * <ul>
     *     <li>Field: uses the field name.</li>
     *     <li>Method: when named <code>set<var>XYZ</var></code> or <code>with<var>XYZ</var></code>, uses the rest
     *     (<var>XYZ</var>) of the method name. Otherwise, uses the name of the first parameter.</li>
     *     <li>Parameter: uses the parameter name.</li>
     * </ul>
     * @return the value;
     */
    String value() default Strings.EMPTY;

    /**
     * Indicates that this attribute is a sensitive one that shouldn't be logged directly. Such attributes will instead
     * be output as a hashed value.
     * @return true if the attribute should be considered sensitive.
     */
    boolean sensitive() default false;

}