    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 *     http://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.beanutils;
    018
    019import java.util.Objects;
    020
    021/**
    022 * <p>
    023 * A class representing an argument for a constructor invocation to be used by a
    024 * {@link BeanDeclaration}.
    025 * </p>
    026 * <p>
    027 * A {@code BeanDeclaration} can provide a list of instances of this class to
    028 * define the constructor to be invoked on the bean class. Each constructor
    029 * argument can either be a simple value or a nested {@code BeanDeclaration}. In
    030 * the latter case, the bean is resolved recursively.
    031 * </p>
    032 * <p>
    033 * The constructor to be invoked on the bean class has to be determined based on
    034 * the types of the constructor arguments. To avoid ambiguity, the type name can
    035 * be explicitly provided.
    036 * </p>
    037 *
    038 * @since 2.0
    039 */
    040public final class ConstructorArg
    041{
    042    /** The bean declaration referenced by this constructor argument. */
    043    private final BeanDeclaration beanDeclaration;
    044
    045    /** The value of this constructor argument. */
    046    private final Object value;
    047
    048    /** The name of the argument type. */
    049    private final String typeName;
    050
    051    /**
    052     * Creates a new instance of {@code ConstructorArg}.
    053     *
    054     * @param decl the associated bean declaration
    055     * @param val the value of the argument
    056     * @param type the type name
    057     */
    058    private ConstructorArg(final BeanDeclaration decl, final Object val, final String type)
    059    {
    060        beanDeclaration = decl;
    061        value = val;
    062        typeName = type;
    063    }
    064
    065    /**
    066     * Creates a new instance of {@code ConstructorArg} for the specified
    067     * {@code BeanDeclaration}. The actual value of this argument is the
    068     * resolved {@code BeanDeclaration}.
    069     *
    070     * @param decl the {@code BeanDeclaration}
    071     * @return the newly created instance of this class
    072     * @throws NullPointerException if the {@code BeanDeclaration} is
    073     *         <b>null</b>
    074     */
    075    public static ConstructorArg forBeanDeclaration(final BeanDeclaration decl)
    076    {
    077        return forBeanDeclaration(decl, null);
    078    }
    079
    080    /**
    081     * Creates a new instance of {@code ConstructorArg} for the specified
    082     * {@code BeanDeclaration} and sets the type name explicitly. The type name
    083     * is used to match this argument against the parameter type of a
    084     * constructor or the bean class.
    085     *
    086     * @param beanDeclaration the {@code BeanDeclaration}
    087     * @param typeName the name of the data type of this argument
    088     * @return the newly created instance of this class
    089     * @throws NullPointerException if the {@code BeanDeclaration} is
    090     *         <b>null</b>
    091     */
    092    public static ConstructorArg forBeanDeclaration(final BeanDeclaration beanDeclaration,
    093            final String typeName)
    094    {
    095        Objects.requireNonNull(beanDeclaration, "beanDeclaration");
    096        return new ConstructorArg(beanDeclaration, null, typeName);
    097    }
    098
    099    /**
    100     * Creates a new instance of {@code ConstructorArg} for the specified simple
    101     * value. The value is passed to the constructor invocation.
    102     *
    103     * @param value the value of this constructor argument (may be <b>null</b>)
    104     * @return the newly created instance of this class
    105     */
    106    public static ConstructorArg forValue(final Object value)
    107    {
    108        return forValue(value, null);
    109    }
    110
    111    /**
    112     * Creates a new instance of {@code ConstructorArg} for the specified simple
    113     * value and sets the type name explicitly. The type name is used to match
    114     * this argument against the parameter type of a constructor or the bean
    115     * class.
    116     *
    117     * @param value the value of this constructor argument (may be <b>null</b>)
    118     * @param typeName the name of the data type of this argument
    119     * @return the newly created instance of this class
    120     */
    121    public static ConstructorArg forValue(final Object value, final String typeName)
    122    {
    123        return new ConstructorArg(null, value, typeName);
    124    }
    125
    126    /**
    127     * Returns the {@code BeanDeclaration} referenced by this constructor
    128     * argument. A return value of <b>null</b> means that this constructor
    129     * argument does not have a bean declaration as value; in this case, the
    130     * value can be queried using the {@link #getValue()} method.
    131     *
    132     * @return the referenced {@code BeanDeclaration} or <b>null</b>
    133     */
    134    public BeanDeclaration getBeanDeclaration()
    135    {
    136        return beanDeclaration;
    137    }
    138
    139    /**
    140     * Returns a flag whether this constructor argument represents a
    141     * {@code BeanDeclaration}. If this method returns <b>true</b>, the actual
    142     * value of this argument can be obtained by resolving the bean declaration
    143     * returned by {@link #getBeanDeclaration()}. Otherwise, this argument has a
    144     * simple value which can be queried using {@link #getValue()}.
    145     *
    146     * @return a flag whether this constructor argument references a bean
    147     *         declaration
    148     */
    149    public boolean isNestedBeanDeclaration()
    150    {
    151        return getBeanDeclaration() != null;
    152    }
    153
    154    /**
    155     * Returns the value of this constructor argument. This method can be
    156     * queried if {@link #isNestedBeanDeclaration()} returns <b>false</b>. Note
    157     * that a return value of <b>null</b> is legal (to pass <b>null</b> to a
    158     * constructor argument).
    159     *
    160     * @return the simple value of this constructor argument
    161     */
    162    public Object getValue()
    163    {
    164        return value;
    165    }
    166
    167    /**
    168     * Returns the optional data type name of this constructor argument. The
    169     * type name can be specified as a hint to select a specific constructor if
    170     * there are ambiguities. Note that it does not necessarily has to match the
    171     * data type of this argument's value because a type conversion may be
    172     * performed before invoking the constructor.
    173     *
    174     * @return the data type name of this argument if defined or <b>null</b>
    175     *         otherwise
    176     */
    177    public String getTypeName()
    178    {
    179        return typeName;
    180    }
    181
    182    /**
    183     * Checks whether this constructor argument is compatible with the given
    184     * class. This method is called to determine a matching constructor. It
    185     * compares the argument's data type with the class name if it is defined.
    186     * If no type name has been set, result is <b>true</b> as it is assumed that
    187     * a type conversion can be performed when calling the constructor. This
    188     * means that per default only the number of constructor arguments is
    189     * checked to find a matching constructor. Only if there are multiple
    190     * constructors with the same number of arguments, explicit type names have
    191     * to be provided to select a specific constructor.
    192     *
    193     * @param argCls the class of the constructor argument to compare with
    194     * @return <b>true</b> if this constructor argument is compatible with this
    195     *         class, <b>false</b> otherwise
    196     */
    197    public boolean matches(final Class<?> argCls)
    198    {
    199        if (argCls == null)
    200        {
    201            return false;
    202        }
    203
    204        return getTypeName() == null || getTypeName().equals(argCls.getName());
    205    }
    206
    207    /**
    208     * Returns a string representation of this object. This string contains the
    209     * value of this constructor argument and the explicit type if provided.
    210     *
    211     * @return a string for this object
    212     */
    213    @Override
    214    public String toString()
    215    {
    216        final StringBuilder buf = new StringBuilder();
    217        buf.append(getClass().getSimpleName());
    218        buf.append(" [ value = ");
    219        buf.append(isNestedBeanDeclaration() ? getBeanDeclaration()
    220                : getValue());
    221        if (getTypeName() != null)
    222        {
    223            buf.append(" (").append(getTypeName()).append(')');
    224        }
    225        buf.append(" ]");
    226        return buf.toString();
    227    }
    228}