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Tools to assist in the reading of configuration/preferences files in
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/*
* 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.commons.configuration2.beanutils;
/**
*
* A class representing an argument for a constructor invocation to be used by a
* {@link BeanDeclaration}.
*
*
* A {@code BeanDeclaration} can provide a list of instances of this class to
* define the constructor to be invoked on the bean class. Each constructor
* argument can either be a simple value or a nested {@code BeanDeclaration}. In
* the latter case, the bean is resolved recursively.
*
*
* The constructor to be invoked on the bean class has to be determined based on
* the types of the constructor arguments. To avoid ambiguity, the type name can
* be explicitly provided.
*
*
* @version $Id: ConstructorArg.java 1842194 2018-09-27 22:24:23Z ggregory $
* @since 2.0
*/
public final class ConstructorArg
{
/** The bean declaration referenced by this constructor argument. */
private final BeanDeclaration beanDeclaration;
/** The value of this constructor argument. */
private final Object value;
/** The name of the argument type. */
private final String typeName;
/**
* Creates a new instance of {@code ConstructorArg}.
*
* @param decl the associated bean declaration
* @param val the value of the argument
* @param type the type name
*/
private ConstructorArg(final BeanDeclaration decl, final Object val, final String type)
{
beanDeclaration = decl;
value = val;
typeName = type;
}
/**
* Creates a new instance of {@code ConstructorArg} for the specified
* {@code BeanDeclaration}. The actual value of this argument is the
* resolved {@code BeanDeclaration}.
*
* @param decl the {@code BeanDeclaration}
* @return the newly created instance of this class
* @throws NullPointerException if the {@code BeanDeclaration} is
* null
*/
public static ConstructorArg forBeanDeclaration(final BeanDeclaration decl)
{
return forBeanDeclaration(decl, null);
}
/**
* Creates a new instance of {@code ConstructorArg} for the specified
* {@code BeanDeclaration} and sets the type name explicitly. The type name
* is used to match this argument against the parameter type of a
* constructor or the bean class.
*
* @param decl the {@code BeanDeclaration}
* @param typeName the name of the data type of this argument
* @return the newly created instance of this class
* @throws NullPointerException if the {@code BeanDeclaration} is
* null
*/
public static ConstructorArg forBeanDeclaration(final BeanDeclaration decl,
final String typeName)
{
if (decl == null)
{
throw new NullPointerException("BeanDeclaration must not be null!");
}
return new ConstructorArg(decl, null, typeName);
}
/**
* Creates a new instance of {@code ConstructorArg} for the specified simple
* value. The value is passed to the constructor invocation.
*
* @param value the value of this constructor argument (may be null)
* @return the newly created instance of this class
*/
public static ConstructorArg forValue(final Object value)
{
return forValue(value, null);
}
/**
* Creates a new instance of {@code ConstructorArg} for the specified simple
* value and sets the type name explicitly. The type name is used to match
* this argument against the parameter type of a constructor or the bean
* class.
*
* @param value the value of this constructor argument (may be null)
* @param typeName the name of the data type of this argument
* @return the newly created instance of this class
*/
public static ConstructorArg forValue(final Object value, final String typeName)
{
return new ConstructorArg(null, value, typeName);
}
/**
* Returns the {@code BeanDeclaration} referenced by this constructor
* argument. A return value of null means that this constructor
* argument does not have a bean declaration as value; in this case, the
* value can be queried using the {@link #getValue()} method.
*
* @return the referenced {@code BeanDeclaration} or null
*/
public BeanDeclaration getBeanDeclaration()
{
return beanDeclaration;
}
/**
* Returns a flag whether this constructor argument represents a
* {@code BeanDeclaration}. If this method returns true, the actual
* value of this argument can be obtained by resolving the bean declaration
* returned by {@link #getBeanDeclaration()}. Otherwise, this argument has a
* simple value which can be queried using {@link #getValue()}.
*
* @return a flag whether this constructor argument references a bean
* declaration
*/
public boolean isNestedBeanDeclaration()
{
return getBeanDeclaration() != null;
}
/**
* Returns the value of this constructor argument. This method can be
* queried if {@link #isNestedBeanDeclaration()} returns false. Note
* that a return value of null is legal (to pass null to a
* constructor argument).
*
* @return the simple value of this constructor argument
*/
public Object getValue()
{
return value;
}
/**
* Returns the optional data type name of this constructor argument. The
* type name can be specified as a hint to select a specific constructor if
* there are ambiguities. Note that it does not necessarily has to match the
* data type of this argument's value because a type conversion may be
* performed before invoking the constructor.
*
* @return the data type name of this argument if defined or null
* otherwise
*/
public String getTypeName()
{
return typeName;
}
/**
* Checks whether this constructor argument is compatible with the given
* class. This method is called to determine a matching constructor. It
* compares the argument's data type with the class name if it is defined.
* If no type name has been set, result is true as it is assumed that
* a type conversion can be performed when calling the constructor. This
* means that per default only the number of constructor arguments is
* checked to find a matching constructor. Only if there are multiple
* constructors with the same number of arguments, explicit type names have
* to be provided to select a specific constructor.
*
* @param argCls the class of the constructor argument to compare with
* @return true if this constructor argument is compatible with this
* class, false otherwise
*/
public boolean matches(final Class argCls)
{
if (argCls == null)
{
return false;
}
return getTypeName() == null || getTypeName().equals(argCls.getName());
}
/**
* Returns a string representation of this object. This string contains the
* value of this constructor argument and the explicit type if provided.
*
* @return a string for this object
*/
@Override
public String toString()
{
final StringBuilder buf = new StringBuilder();
buf.append(getClass().getSimpleName());
buf.append(" [ value = ");
buf.append(isNestedBeanDeclaration() ? getBeanDeclaration()
: getValue());
if (getTypeName() != null)
{
buf.append(" (").append(getTypeName()).append(')');
}
buf.append(" ]");
return buf.toString();
}
}