Source code
Description: source: package: org.apache.commons.configuration2.beanutils, class: ConstructorArg

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