    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     https://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.builder;
    018
    019import java.util.Collection;
    020import java.util.Collections;
    021import java.util.HashMap;
    022import java.util.Map;
    023
    024import org.apache.commons.configuration2.ConfigurationUtils;
    025import org.apache.commons.configuration2.ImmutableConfiguration;
    026import org.apache.commons.configuration2.Initializable;
    027import org.apache.commons.configuration2.beanutils.BeanDeclaration;
    028import org.apache.commons.configuration2.beanutils.BeanHelper;
    029import org.apache.commons.configuration2.beanutils.ConstructorArg;
    030import org.apache.commons.configuration2.event.Event;
    031import org.apache.commons.configuration2.event.EventListener;
    032import org.apache.commons.configuration2.event.EventListenerList;
    033import org.apache.commons.configuration2.event.EventListenerRegistrationData;
    034import org.apache.commons.configuration2.event.EventSource;
    035import org.apache.commons.configuration2.event.EventType;
    036import org.apache.commons.configuration2.ex.ConfigurationException;
    037import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    038import org.apache.commons.configuration2.reloading.ReloadingController;
    039
    040/**
    041 * <p>
    042 * An implementation of the {@code ConfigurationBuilder} interface which is able to create different concrete
    043 * {@code ImmutableConfiguration} implementations based on reflection.
    044 * </p>
    045 * <p>
    046 * When constructing an instance of this class the concrete {@code ImmutableConfiguration} implementation class has to
    047 * be provided. Then properties for the new {@code ImmutableConfiguration} instance can be set. The first call to
    048 * {@code getConfiguration()} creates and initializes the new {@code ImmutableConfiguration} object. It is cached and
    049 * returned by subsequent calls. This cache - and also the initialization properties set so far - can be flushed by
    050 * calling one of the {@code reset()} methods. That way other {@code ImmutableConfiguration} instances with different
    051 * properties can be created.
    052 * </p>
    053 * <p>
    054 * If the newly created {@code ImmutableConfiguration} object implements the {@code Initializable} interface, its
    055 * {@code initialize()} method is called after all initialization properties have been set. This way a concrete
    056 * implementation class can perform arbitrary initialization steps.
    057 * </p>
    058 * <p>
    059 * There are multiple options for setting up a {@code BasicConfigurationBuilder} instance:
    060 * </p>
    061 * <ul>
    062 * <li>All initialization properties can be set in one or multiple calls of the {@code configure()} method. In each call
    063 * an arbitrary number of {@link BuilderParameters} objects can be passed. The API allows method chaining and is
    064 * intended to be used from Java code.</li>
    065 * <li>If builder instances are created by other means - for example using a dependency injection framework -, the fluent API
    066 * approach may not be suitable. For those use cases it is also possible to pass in all initialization parameters as a
    067 * map. The keys of the map have to match initialization properties of the {@code ImmutableConfiguration} object to be
    068 * created, the values are the corresponding property values. For instance, the key <em>throwExceptionOnMissing</em> in
    069 * the map will cause the method {@code setThrowExceptionOnMissing()} on the {@code ImmutableConfiguration} object to be
    070 * called with the corresponding value as parameter.</li>
    071 * </ul>
    072 * <p>
    073 * A builder instance can be constructed with an <em>allowFailOnInit</em> flag. If set to <strong>true</strong>,
    074 * exceptions during initialization of the configuration are ignored; in such a case an empty configuration object is
    075 * returned. A use case for this flag is a scenario in which a configuration is optional and created on demand the first
    076 * time configuration data is to be stored. Consider an application that stores user-specific configuration data in the
    077 * user's home directory: When started for the first time by a new user there is no configuration file; so it makes
    078 * sense to start with an empty configuration object. On application exit, settings can be stored in this object and
    079 * written to the associated file. Then they are available on next application start.
    080 * </p>
    081 * <p>
    082 * This class is thread-safe. Multiple threads can modify initialization properties and call {@code getConfiguration()}.
    083 * However, the intended use case is that the builder is configured by a single thread first. Then
    084 * {@code getConfiguration()} can be called concurrently, and it is guaranteed that always the same
    085 * {@code ImmutableConfiguration} instance is returned until the builder is reset.
    086 * </p>
    087 *
    088 * @param <T> the concrete type of {@code ImmutableConfiguration} objects created by this builder
    089 * @since 2.0
    090 */
    091public class BasicConfigurationBuilder<T extends ImmutableConfiguration> implements ConfigurationBuilder<T> {
    092
    093    /**
    094     * Registers an event listener at an event source object.
    095     *
    096     * @param evSrc the event source
    097     * @param regData the registration data object
    098     * @param <E> the type of the event listener
    099     */
    100    private static <E extends Event> void registerListener(final EventSource evSrc, final EventListenerRegistrationData<E> regData) {
    101        evSrc.addEventListener(regData.getEventType(), regData.getListener());
    102    }
    103
    104    /**
    105     * Removes an event listener from an event source object.
    106     *
    107     * @param evSrc the event source
    108     * @param regData the registration data object
    109     * @param <E> the type of the event listener
    110     */
    111    private static <E extends Event> void removeListener(final EventSource evSrc, final EventListenerRegistrationData<E> regData) {
    112        evSrc.removeEventListener(regData.getEventType(), regData.getListener());
    113    }
    114
    115    /** The class of the objects produced by this builder instance. */
    116    private final Class<? extends T> resultClass;
    117
    118    /** An object managing the event listeners registered at this builder. */
    119    private final EventListenerList eventListeners;
    120
    121    /** A flag whether exceptions on initializing configurations are allowed. */
    122    private final boolean allowFailOnInit;
    123
    124    /** The map with current initialization parameters. */
    125    private Map<String, Object> parameters;
    126
    127    /** The current bean declaration. */
    128    private BeanDeclaration resultDeclaration;
    129
    130    /** The result object of this builder. */
    131    private volatile T result;
    132
    133    /**
    134     * Creates a new instance of {@code BasicConfigurationBuilder} and initializes it with the given result class. No
    135     * initialization properties are set.
    136     *
    137     * @param resCls the result class (must not be <strong>null</strong>)
    138     * @throws IllegalArgumentException if the result class is <strong>null</strong>
    139     */
    140    public BasicConfigurationBuilder(final Class<? extends T> resCls) {
    141        this(resCls, null);
    142    }
    143
    144    /**
    145     * Creates a new instance of {@code BasicConfigurationBuilder} and initializes it with the given result class and an
    146     * initial set of builder parameters. The <em>allowFailOnInit</em> flag is set to <strong>false</strong>.
    147     *
    148     * @param resCls the result class (must not be <strong>null</strong>)
    149     * @param params a map with initialization parameters
    150     * @throws IllegalArgumentException if the result class is <strong>null</strong>
    151     */
    152    public BasicConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params) {
    153        this(resCls, params, false);
    154    }
    155
    156    /**
    157     * Creates a new instance of {@code BasicConfigurationBuilder} and initializes it with the given result class, an
    158     * initial set of builder parameters, and the <em>allowFailOnInit</em> flag. The map with parameters may be <strong>null</strong>,
    159     * in this case no initialization parameters are set.
    160     *
    161     * @param resCls the result class (must not be <strong>null</strong>)
    162     * @param params a map with initialization parameters
    163     * @param allowFailOnInit a flag whether exceptions on initializing a newly created {@code ImmutableConfiguration}
    164     *        object are allowed
    165     * @throws IllegalArgumentException if the result class is <strong>null</strong>
    166     */
    167    public BasicConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params, final boolean allowFailOnInit) {
    168        if (resCls == null) {
    169            throw new IllegalArgumentException("Result class must not be null!");
    170        }
    171
    172        resultClass = resCls;
    173        this.allowFailOnInit = allowFailOnInit;
    174        eventListeners = new EventListenerList();
    175        updateParameters(params);
    176    }
    177
    178    /**
    179     * {@inheritDoc} This implementation also takes care that the event listener is added to the managed configuration
    180     * object.
    181     *
    182     * @throws IllegalArgumentException if the event type or the listener is <strong>null</strong>
    183     */
    184    @Override
    185    public <E extends Event> void addEventListener(final EventType<E> eventType, final EventListener<? super E> listener) {
    186        installEventListener(eventType, listener);
    187    }
    188
    189    /**
    190     * Adds the content of the given map to the already existing initialization parameters.
    191     *
    192     * @param params the map with additional initialization parameters; may be <strong>null</strong>, then this call has no effect
    193     * @return a reference to this builder for method chaining
    194     */
    195    public synchronized BasicConfigurationBuilder<T> addParameters(final Map<String, Object> params) {
    196        final Map<String, Object> newParams = new HashMap<>(getParameters());
    197        if (params != null) {
    198            newParams.putAll(params);
    199        }
    200        updateParameters(newParams);
    201        return this;
    202    }
    203
    204    /**
    205     * Checks whether the class of the result configuration is compatible with this builder's result class. This is done to
    206     * ensure that only objects of the expected result class are created.
    207     *
    208     * @param inst the result instance to be checked
    209     * @throws ConfigurationRuntimeException if an invalid result class is detected
    210     */
    211    private void checkResultInstance(final Object inst) {
    212        if (!getResultClass().isInstance(inst)) {
    213            throw new ConfigurationRuntimeException("Incompatible result object: " + inst);
    214        }
    215    }
    216
    217    /**
    218     * Appends the content of the specified {@code BuilderParameters} objects to the current initialization parameters.
    219     * Calling this method multiple times will create a union of the parameters provided.
    220     *
    221     * @param params an arbitrary number of objects with builder parameters
    222     * @return a reference to this builder for method chaining
    223     * @throws NullPointerException if a <strong>null</strong> array is passed
    224     */
    225    public BasicConfigurationBuilder<T> configure(final BuilderParameters... params) {
    226        final Map<String, Object> newParams = new HashMap<>();
    227        for (final BuilderParameters p : params) {
    228            newParams.putAll(p.getParameters());
    229            handleEventListenerProviders(p);
    230        }
    231        return setParameters(newParams);
    232    }
    233
    234    /**
    235     * Connects this builder with a {@code ReloadingController}. With this method support for reloading can be added to an
    236     * arbitrary builder object. Event listeners are registered at the reloading controller and this builder with connect
    237     * both objects:
    238     * <ul>
    239     * <li>When the reloading controller detects that a reload is required, the builder's {@link #resetResult()} method is
    240     * called; so the managed result object is invalidated.</li>
    241     * <li>When a new result object has been created the controller's reloading state is reset, so that new changes can be
    242     * detected again.</li>
    243     * </ul>
    244     *
    245     * @param controller the {@code ReloadingController} to connect to (must not be <strong>null</strong>)
    246     * @throws IllegalArgumentException if the controller is <strong>null</strong>
    247     */
    248    public final void connectToReloadingController(final ReloadingController controller) {
    249        if (controller == null) {
    250            throw new IllegalArgumentException("ReloadingController must not be null!");
    251        }
    252        ReloadingBuilderSupportListener.connect(this, controller);
    253    }
    254
    255    /**
    256     * Copies all {@code EventListener} objects registered at this builder to the specified target configuration builder.
    257     * This method is intended to be used by derived classes which support inheritance of their properties to other builder
    258     * objects.
    259     *
    260     * @param target the target configuration builder (must not be <strong>null</strong>)
    261     * @throws NullPointerException if the target builder is <strong>null</strong>
    262     */
    263    protected synchronized void copyEventListeners(final BasicConfigurationBuilder<?> target) {
    264        copyEventListeners(target, eventListeners);
    265    }
    266
    267    /**
    268     * Copies all event listeners in the specified list to the specified target configuration builder. This method is
    269     * intended to be used by derived classes which have to deal with managed configuration builders that need to be
    270     * initialized with event listeners.
    271     *
    272     * @param target the target configuration builder (must not be <strong>null</strong>)
    273     * @param listeners the event listeners to be copied over
    274     * @throws NullPointerException if the target builder is <strong>null</strong>
    275     */
    276    protected void copyEventListeners(final BasicConfigurationBuilder<?> target, final EventListenerList listeners) {
    277        target.eventListeners.addAll(listeners);
    278    }
    279
    280    /**
    281     * Creates a new, initialized result object. This method is called by {@code getConfiguration()} if no valid result
    282     * object exists. This base implementation performs two steps:
    283     * <ul>
    284     * <li>{@code createResultInstance()} is called to create a new, uninitialized result object.</li>
    285     * <li>{@code initResultInstance()} is called to process all initialization parameters.</li>
    286     * </ul>
    287     * It also evaluates the <em>allowFailOnInit</em> flag, i.e. if initialization causes an exception and this flag is set,
    288     * the exception is ignored, and the newly created, uninitialized configuration is returned. Note that this method is
    289     * called in a synchronized block.
    290     *
    291     * @return the newly created result object
    292     * @throws ConfigurationException if an error occurs
    293     */
    294    protected T createResult() throws ConfigurationException {
    295        final T resObj = createResultInstance();
    296
    297        try {
    298            initResultInstance(resObj);
    299        } catch (final ConfigurationException cex) {
    300            if (!isAllowFailOnInit()) {
    301                throw cex;
    302            }
    303        }
    304
    305        return resObj;
    306    }
    307
    308    /**
    309     * Creates a new {@code BeanDeclaration} which is used for creating new result objects dynamically. This implementation
    310     * creates a specialized {@code BeanDeclaration} object that is initialized from the given map of initialization
    311     * parameters. The {@code BeanDeclaration} must be initialized with the result class of this builder, otherwise
    312     * exceptions will be thrown when the result object is created. Note: This method is invoked in a synchronized block.
    313     *
    314     * @param params a snapshot of the current initialization parameters
    315     * @return the {@code BeanDeclaration} for creating result objects
    316     * @throws ConfigurationException if an error occurs
    317     */
    318    protected BeanDeclaration createResultDeclaration(final Map<String, Object> params) throws ConfigurationException {
    319        return new BeanDeclaration() {
    320            @Override
    321            public String getBeanClassName() {
    322                return getResultClass().getName();
    323            }
    324
    325            @Override
    326            public String getBeanFactoryName() {
    327                return null;
    328            }
    329
    330            @Override
    331            public Object getBeanFactoryParameter() {
    332                return null;
    333            }
    334
    335            @Override
    336            public Map<String, Object> getBeanProperties() {
    337                // the properties are equivalent to the parameters
    338                return params;
    339            }
    340
    341            @Override
    342            public Collection<ConstructorArg> getConstructorArgs() {
    343                // no constructor arguments
    344                return Collections.emptySet();
    345            }
    346
    347            @Override
    348            public Map<String, Object> getNestedBeanDeclarations() {
    349                // no nested beans
    350                return Collections.emptyMap();
    351            }
    352        };
    353    }
    354
    355    /**
    356     * Creates the new, uninitialized result object. This is the first step of the process of producing a result object for
    357     * this builder. This implementation uses the {@link BeanHelper} class to create a new object based on the
    358     * {@link BeanDeclaration} returned by {@link #getResultDeclaration()}. Note: This method is invoked in a synchronized
    359     * block.
    360     *
    361     * @return the newly created, yet uninitialized result object
    362     * @throws ConfigurationException if an exception occurs
    363     */
    364    protected T createResultInstance() throws ConfigurationException {
    365        final Object bean = fetchBeanHelper().createBean(getResultDeclaration());
    366        checkResultInstance(bean);
    367        return getResultClass().cast(bean);
    368    }
    369
    370    /**
    371     * Obtains the {@code BeanHelper} object to be used when dealing with bean declarations. This method checks whether this
    372     * builder was configured with a specific {@code BeanHelper} instance. If so, this instance is used. Otherwise, the
    373     * default {@code BeanHelper} is returned.
    374     *
    375     * @return the {@code BeanHelper} to be used
    376     */
    377    protected final BeanHelper fetchBeanHelper() {
    378        final BeanHelper helper = BasicBuilderParameters.fetchBeanHelper(getParameters());
    379        return helper != null ? helper : BeanHelper.INSTANCE;
    380    }
    381
    382    /**
    383     * Returns an {@code EventSource} for the current result object. If there is no current result or if it does not extend
    384     * {@code EventSource}, a dummy event source is returned.
    385     *
    386     * @return the {@code EventSource} for the current result object
    387     */
    388    private EventSource fetchEventSource() {
    389        return ConfigurationUtils.asEventSource(result, true);
    390    }
    391
    392    /**
    393     * Sends the specified builder event to all registered listeners.
    394     *
    395     * @param event the event to be fired
    396     */
    397    protected void fireBuilderEvent(final ConfigurationBuilderEvent event) {
    398        eventListeners.fire(event);
    399    }
    400
    401    /**
    402     * {@inheritDoc} This implementation creates the result configuration on first access. Later invocations return the same
    403     * object until this builder is reset. The double-check idiom for lazy initialization is used (Bloch, Effective Java,
    404     * item 71).
    405     */
    406    @Override
    407    public T getConfiguration() throws ConfigurationException {
    408        fireBuilderEvent(new ConfigurationBuilderEvent(this, ConfigurationBuilderEvent.CONFIGURATION_REQUEST));
    409
    410        T resObj = result;
    411        boolean created = false;
    412        if (resObj == null) {
    413            synchronized (this) {
    414                resObj = result;
    415                if (resObj == null) {
    416                    result = resObj = createResult();
    417                    created = true;
    418                }
    419            }
    420        }
    421
    422        if (created) {
    423            fireBuilderEvent(new ConfigurationBuilderResultCreatedEvent(this, ConfigurationBuilderResultCreatedEvent.RESULT_CREATED, resObj));
    424        }
    425        return resObj;
    426    }
    427
    428    /**
    429     * Gets a map with initialization parameters where all parameters starting with the reserved prefix have been
    430     * filtered out.
    431     *
    432     * @return the filtered parameters map
    433     */
    434    private Map<String, Object> getFilteredParameters() {
    435        final Map<String, Object> filteredMap = new HashMap<>(getParameters());
    436        filteredMap.keySet().removeIf(key -> key.startsWith(BuilderParameters.RESERVED_PARAMETER_PREFIX));
    437        return filteredMap;
    438    }
    439
    440    /**
    441     * Gets a (unmodifiable) map with the current initialization parameters set for this builder. The map is populated
    442     * with the parameters set using the various configuration options.
    443     *
    444     * @return a map with the current set of initialization parameters
    445     */
    446    protected final synchronized Map<String, Object> getParameters() {
    447        if (parameters != null) {
    448            return parameters;
    449        }
    450        return Collections.emptyMap();
    451    }
    452
    453    /**
    454     * Gets the result class of this builder. The objects produced by this builder have the class returned here.
    455     *
    456     * @return the result class of this builder
    457     */
    458    public Class<? extends T> getResultClass() {
    459        return resultClass;
    460    }
    461
    462    /**
    463     * Gets the {@code BeanDeclaration} that is used to create and initialize result objects. The declaration is created
    464     * on first access (by invoking {@link #createResultDeclaration(Map)}) based on the current initialization parameters.
    465     *
    466     * @return the {@code BeanDeclaration} for dynamically creating a result object
    467     * @throws ConfigurationException if an error occurs
    468     */
    469    protected final synchronized BeanDeclaration getResultDeclaration() throws ConfigurationException {
    470        if (resultDeclaration == null) {
    471            resultDeclaration = createResultDeclaration(getFilteredParameters());
    472        }
    473        return resultDeclaration;
    474    }
    475
    476    /**
    477     * Checks whether the specified parameters object implements the {@code EventListenerProvider} interface. If so, the
    478     * event listeners it provides are added to this builder.
    479     *
    480     * @param params the parameters object
    481     */
    482    private void handleEventListenerProviders(final BuilderParameters params) {
    483        if (params instanceof EventListenerProvider) {
    484            eventListeners.addAll(((EventListenerProvider) params).getListeners());
    485        }
    486    }
    487
    488    /**
    489     * Performs special initialization of the result object. This method is called after parameters have been set on a newly
    490     * created result instance. If supported by the result class, the {@code initialize()} method is now called.
    491     *
    492     * @param obj the newly created result object
    493     */
    494    private void handleInitializable(final T obj) {
    495        if (obj instanceof Initializable) {
    496            ((Initializable) obj).initialize();
    497        }
    498    }
    499
    500    /**
    501     * Initializes a newly created result object. This is the second step of the process of producing a result object for
    502     * this builder. This implementation uses the {@link BeanHelper} class to initialize the object's property based on the
    503     * {@link BeanDeclaration} returned by {@link #getResultDeclaration()}. Note: This method is invoked in a synchronized
    504     * block. This is required because internal state is accessed. Sub classes must not call this method without proper
    505     * synchronization.
    506     *
    507     * @param obj the object to be initialized
    508     * @throws ConfigurationException if an error occurs
    509     */
    510    protected void initResultInstance(final T obj) throws ConfigurationException {
    511        fetchBeanHelper().initBean(obj, getResultDeclaration());
    512        registerEventListeners(obj);
    513        handleInitializable(obj);
    514    }
    515
    516    /**
    517     * Adds the specified event listener to this object. This method is called by {@code addEventListener()}, it does the
    518     * actual listener registration. Because it is final it can be called by sub classes in the constructor if there is
    519     * already the need to register an event listener.
    520     *
    521     * @param eventType the event type object
    522     * @param listener the listener to be registered
    523     * @param <E> the event type
    524     */
    525    protected final <E extends Event> void installEventListener(final EventType<E> eventType, final EventListener<? super E> listener) {
    526        fetchEventSource().addEventListener(eventType, listener);
    527        eventListeners.addEventListener(eventType, listener);
    528    }
    529
    530    /**
    531     * Returns the <em>allowFailOnInit</em> flag. See the header comment for information about this flag.
    532     *
    533     * @return the <em>allowFailOnInit</em> flag
    534     */
    535    public boolean isAllowFailOnInit() {
    536        return allowFailOnInit;
    537    }
    538
    539    /**
    540     * Registers the available event listeners at the given object. This method is called for each result object created by
    541     * the builder.
    542     *
    543     * @param obj the object to initialize
    544     */
    545    private void registerEventListeners(final T obj) {
    546        final EventSource evSrc = ConfigurationUtils.asEventSource(obj, true);
    547        eventListeners.getRegistrations().forEach(regData -> registerListener(evSrc, regData));
    548    }
    549
    550    /**
    551     * {@inheritDoc} This implementation also takes care that the event listener is removed from the managed configuration
    552     * object.
    553     */
    554    @Override
    555    public <E extends Event> boolean removeEventListener(final EventType<E> eventType, final EventListener<? super E> listener) {
    556        fetchEventSource().removeEventListener(eventType, listener);
    557        return eventListeners.removeEventListener(eventType, listener);
    558    }
    559
    560    /**
    561     * Removes all available event listeners from the given result object. This method is called when the result of this
    562     * builder is reset. Then the old managed configuration should no longer generate events.
    563     *
    564     * @param obj the affected result object
    565     */
    566    private void removeEventListeners(final T obj) {
    567        final EventSource evSrc = ConfigurationUtils.asEventSource(obj, true);
    568        eventListeners.getRegistrations().forEach(regData -> removeListener(evSrc, regData));
    569    }
    570
    571    /**
    572     * Resets this builder. This is a convenience method which combines calls to {@link #resetResult()} and
    573     * {@link #resetParameters()}.
    574     */
    575    public synchronized void reset() {
    576        resetParameters();
    577        resetResult();
    578    }
    579
    580    /**
    581     * Removes all initialization parameters of this builder. This method can be called if this builder is to be reused for
    582     * creating result objects with a different configuration.
    583     */
    584    public void resetParameters() {
    585        setParameters(null);
    586    }
    587
    588    /**
    589     * Clears an existing result object. An invocation of this method causes a new {@code ImmutableConfiguration} object to
    590     * be created the next time {@link #getConfiguration()} is called.
    591     */
    592    public void resetResult() {
    593        final T oldResult;
    594        synchronized (this) {
    595            oldResult = result;
    596            result = null;
    597            resultDeclaration = null;
    598        }
    599
    600        if (oldResult != null) {
    601            removeEventListeners(oldResult);
    602        }
    603        fireBuilderEvent(new ConfigurationBuilderEvent(this, ConfigurationBuilderEvent.RESET));
    604    }
    605
    606    /**
    607     * Sets the initialization parameters of this builder. Already existing parameters are replaced by the content of the
    608     * given map.
    609     *
    610     * @param params the new initialization parameters of this builder; can be <strong>null</strong>, then all initialization
    611     *        parameters are removed
    612     * @return a reference to this builder for method chaining
    613     */
    614    public synchronized BasicConfigurationBuilder<T> setParameters(final Map<String, Object> params) {
    615        updateParameters(params);
    616        return this;
    617    }
    618
    619    /**
    620     * Replaces the current map with parameters by a new one.
    621     *
    622     * @param newParams the map with new parameters (may be <strong>null</strong>)
    623     */
    624    private void updateParameters(final Map<String, Object> newParams) {
    625        final Map<String, Object> map = new HashMap<>();
    626        if (newParams != null) {
    627            map.putAll(newParams);
    628        }
    629        parameters = Collections.unmodifiableMap(map);
    630    }
    631}