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/*
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* Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package jdk.jfr;
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import java.security.AccessController;
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import java.util.Set;
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import jdk.jfr.internal.Control;
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/**
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* Base class to extend to create setting controls.
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* <p>
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* The following example shows a naive implementation of a setting control for
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* regular expressions:
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*
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* <pre>
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* <code>
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* final class RegExpControl extends SettingControl {
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* private Pattern pattern = Pattern.compile(".*");
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*
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* {@literal @}Override
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* public void setValue(String value) {
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* this.pattern = Pattern.compile(value);
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* }
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*
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* {@literal @}Override
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* public String combine(Set{@literal <}String{@literal >} values) {
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* return String.join("|", values);
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* }
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*
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* {@literal @}Override
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* public String getValue() {
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* return pattern.toString();
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* }
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*
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* public String matches(String s) {
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* return pattern.matcher(s).find();
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* }
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* }
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* </code>
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* </pre>
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*
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* The {@code setValue(String)}, {@code getValue()} and
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* {@code combine(Set<String>)} methods are invoked when a setting value
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* changes, which typically happens when a recording is started or stopped. The
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* {@code combine(Set<String>)} method is invoked to resolve what value to use
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* when multiple recordings are running at the same time.
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* <p>
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* The setting control must have a default constructor that can be invoked when
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* the event is registered.
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* <p>
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* To use a setting control with an event, add a method that returns a
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* {@code boolean} value and takes the setting control as a parameter. Annotate
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* the method with the {@code @SettingDefinition} annotation. By default, the
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* method name is used as the setting name, but the name can be set explicitly
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* by using the {@code @Name} annotation. If the method returns {@code true},
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* the event will be committed.
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* <p>
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* It is recommended that the {@code setValue(String)} method updates an
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* efficient data structure that can be quickly checked when the event is
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* committed.
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* <p>
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* The following example shows how to create an event that uses the
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* regular expression filter defined above.
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*
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* <pre>
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* <code>
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* abstract class HTTPRequest extends Event {
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* {@literal @}Label("Request URI")
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* protected String uri;
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*
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* {@literal @}Label("Servlet URI Filter")
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* {@literal @}SettingDefinition
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* protected boolean uriFilter(RegExpControl regExp) {
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* return regExp.matches(uri);
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* }
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* }
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*
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* {@literal @}Label("HTTP Get Request")
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* class HTTPGetRequest extends HTTPRequest {
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* }
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*
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* {@literal @}Label("HTTP Post Request")
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* class HTTPPostRequest extends HTTPRequest {
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* }
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*
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* class ExampleServlet extends HTTPServlet {
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* protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
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* HTTPGetRequest request = new HTTPGetRequest();
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* request.begin();
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* request.uri = req.getRequestURI();
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* ...
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* request.commit();
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* }
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*
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* protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
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* HTTPPostRequest request = new HTTPPostRequest();
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* request.begin();
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* request.uri = req.getRequestURI();
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* ...
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* request.commit();
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* }
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* }
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* </code>
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* </pre>
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*
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* The following example shows how an event can be filtered by assigning the
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* {@code "uriFilter"} setting with the specified regular expressions.
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*
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* <pre>
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* <code>
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* Recording r = new Recording();
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* r.enable("HTTPGetRequest").with("uriFilter", "https://www.example.com/list/.*");
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* r.enable("HTTPPostRequest").with("uriFilter", "https://www.example.com/login/.*");
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* r.start();
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* </code>
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* </pre>
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*
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*
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*
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* @see SettingDefinition
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*
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* @since 9
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*/
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@MetadataDefinition
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public abstract class SettingControl extends Control {
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/**
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* Constructor for invocation by subclass constructors.
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*/
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protected SettingControl() {
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super(AccessController.getContext());
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}
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/**
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* Combines the setting values for all running recordings into one value when
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* multiple recordings are running at the same time,
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* <p>
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* The semantics of how setting values are combined depends on the setting
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* control that is implemented, but all recordings should get at least all the
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* events they request.
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* <p>
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* This method should have no side effects, because the caller might cache values.
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* This method should never return {@code null} or throw an exception. If a
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* value is not valid for this setting control, the value should be ignored.
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* <p>
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* Examples:
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* <p>
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* if the setting control represents a threshold and three recordings are
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* running at the same time with the setting values {@code "10 ms"},
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* {@code "8 s"}, and {@code "1 ms"}, this method returns {@code "1 ms"}
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* because it means that all recordings get at least all the requested data.
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* <p>
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* If the setting control represents a set of names and two recordings are
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* running at the same time with the setting values {@code "Smith, Jones"} and {@code "Jones,
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* Williams"} the returned value is {@code "Smith, Jones, Williams"} because all names would be accepted.
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* <p>
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* If the setting control represents a boolean condition and four recordings are
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* running at the same time with the following values {@code "true"}, {@code "false"}, {@code "false"}, and
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* {@code "incorrect"}, this method returns {@code "true"}, because all
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* recordings get at least all the requested data.
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*
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* @param settingValues the set of values, not {@code null}
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*
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* @return the value to use, not {@code null}
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*/
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@Override
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public abstract String combine(Set<String> settingValues);
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/**
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* Sets the value for this setting.
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* <p>
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* If the setting value is not valid for this setting, this method
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* does not throw an exception. Instead, the value is ignored.
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*
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* @param settingValue the string value, not {@code null}
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*/
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@Override
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public abstract void setValue(String settingValue);
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/**
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* Returns the currently used value for this setting, not {@code null}.
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* <p>
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* The value returned by this method is valid as an argument to both
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* the {@code setValue(String)} method and {@code combine(Set)} method.
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* <p>
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* This method is invoked when an event is registered to obtain the
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* default value. It is therefore important that a valid value can be
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* returned immediately after an instance of this class is created. It is
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* not valid to return {@code null}.
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*
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* @return the setting value, not {@code null}
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*/
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@Override
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public abstract String getValue();
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}
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