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Apache Commons BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
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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.beanutils2;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
/**
* Minimal implementation of the {@code DynaClass} interface. Can be
* used as a convenience base class for more sophisticated implementations.
* IMPLEMENTATION NOTE - The {@code DynaBean}
* implementation class supplied to our constructor MUST have a one-argument
* constructor of its own that accepts a {@code DynaClass}. This is
* used to associate the DynaBean instance with this DynaClass.
*
*/
public class BasicDynaClass implements DynaClass, Serializable {
private static final long serialVersionUID = 1L;
/**
* Constructs a new BasicDynaClass with default parameters.
*/
public BasicDynaClass() {
this(null, null, null);
}
/**
* Constructs a new BasicDynaClass with the specified parameters.
*
* @param name Name of this DynaBean class
* @param dynaBeanClass The implementation class for new instances
*/
public BasicDynaClass(final String name, final Class dynaBeanClass) {
this(name, dynaBeanClass, null);
}
/**
* Constructs a new BasicDynaClass with the specified parameters.
*
* @param name Name of this DynaBean class
* @param dynaBeanClass The implementation class for new instances
* @param properties Property descriptors for the supported properties
*/
public BasicDynaClass(final String name, Class dynaBeanClass,
final DynaProperty[] properties) {
if (name != null) {
this.name = name;
}
if (dynaBeanClass == null) {
dynaBeanClass = BasicDynaBean.class;
}
setDynaBeanClass(dynaBeanClass);
if (properties != null) {
setProperties(properties);
}
}
/**
* The constructor of the {@code dynaBeanClass} that we will use
* for creating new instances.
*/
protected transient Constructor constructor;
/**
* The method signature of the constructor we will use to create
* new DynaBean instances.
*/
protected static Class[] constructorTypes = { DynaClass.class };
/**
* The argument values to be passed to the constructor we will use
* to create new DynaBean instances.
*/
protected Object[] constructorValues = { this };
/**
* The {@code DynaBean} implementation class we will use for
* creating new instances.
*/
protected Class dynaBeanClass = BasicDynaBean.class;
/**
* The "name" of this DynaBean class.
*/
protected String name = this.getClass().getName();
/**
* The set of dynamic properties that are part of this DynaClass.
*/
protected DynaProperty[] properties = DynaProperty.EMPTY_DYNA_PROPERTY_ARRAY;
/**
* The set of dynamic properties that are part of this DynaClass,
* keyed by the property name. Individual descriptor instances will
* be the same instances as those in the {@code properties} list.
*/
protected HashMap propertiesMap = new HashMap<>();
/**
* Gets the name of this DynaClass (analogous to the
* {@code getName()} method of {@code java.lang.Class}, which
* allows the same {@code DynaClass} implementation class to support
* different dynamic classes, with different sets of properties.
*
* @return the name of the DynaClass
*/
@Override
public String getName() {
return this.name;
}
/**
* Gets a property descriptor for the specified property, if it exists;
* otherwise, return {@code null}.
*
* @param name Name of the dynamic property for which a descriptor
* is requested
* @return The descriptor for the specified property
*
* @throws IllegalArgumentException if no property name is specified
*/
@Override
public DynaProperty getDynaProperty(final String name) {
if (name == null) {
throw new IllegalArgumentException
("No property name specified");
}
return propertiesMap.get(name);
}
/**
* Return an array of {@code PropertyDescriptor} for the properties
* currently defined in this DynaClass. If no properties are defined, a
* zero-length array will be returned.
*
* FIXME - Should we really be implementing
* {@code getBeanInfo()} instead, which returns property descriptors
* and a bunch of other stuff?
*
* @return the set of properties for this DynaClass
*/
@Override
public DynaProperty[] getDynaProperties() {
return properties;
}
/**
* Instantiate and return a new DynaBean instance, associated
* with this DynaClass.
*
* @return A new {@code DynaBean} instance
* @throws IllegalAccessException if the Class or the appropriate
* constructor is not accessible
* @throws InstantiationException if this Class represents an abstract
* class, an array class, a primitive type, or void; or if instantiation
* fails for some other reason
*/
@Override
public DynaBean newInstance()
throws IllegalAccessException, InstantiationException {
try {
// Refind the constructor after a deserialization (if needed)
if (constructor == null) {
setDynaBeanClass(this.dynaBeanClass);
}
// Invoke the constructor to create a new bean instance
return (DynaBean) constructor.newInstance(constructorValues);
} catch (final InvocationTargetException e) {
throw new InstantiationException
(e.getTargetException().getMessage());
}
}
/**
* Gets the Class object we will use to create new instances in the
* {@code newInstance()} method. This Class MUST
* implement the {@code DynaBean} interface.
*
* @return The class of the {@link DynaBean}
*/
public Class getDynaBeanClass() {
return this.dynaBeanClass;
}
/**
* Sets the Class object we will use to create new instances in the
* {@code newInstance()} method. This Class MUST
* implement the {@code DynaBean} interface.
*
* @param dynaBeanClass The new Class object
*
* @throws IllegalArgumentException if the specified Class does not
* implement the {@code DynaBean} interface
*/
protected void setDynaBeanClass(final Class dynaBeanClass) {
// Validate the argument type specified
if (dynaBeanClass.isInterface()) {
throw new IllegalArgumentException
("Class " + dynaBeanClass.getName() +
" is an interface, not a class");
}
if (!DynaBean.class.isAssignableFrom(dynaBeanClass)) {
throw new IllegalArgumentException
("Class " + dynaBeanClass.getName() +
" does not implement DynaBean");
}
// Identify the Constructor we will use in newInstance()
try {
this.constructor = dynaBeanClass.getConstructor(constructorTypes);
} catch (final NoSuchMethodException e) {
throw new IllegalArgumentException
("Class " + dynaBeanClass.getName() +
" does not have an appropriate constructor");
}
this.dynaBeanClass = dynaBeanClass;
}
/**
* Sets the list of dynamic properties supported by this DynaClass.
*
* @param properties List of dynamic properties to be supported
*/
protected void setProperties(final DynaProperty[] properties) {
this.properties = properties;
propertiesMap.clear();
for (final DynaProperty property : properties) {
propertiesMap.put(property.getName(), property);
}
}
}