typeconverterdelegate.java

来自「有关此类编程有心德的高手 希望能够多多给予指教」· Java 代码 · 共 496 行 · 第 1/2 页

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed 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.springframework.beans;

import java.beans.PropertyDescriptor;
import java.beans.PropertyEditor;
import java.beans.PropertyEditorManager;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.WeakHashMap;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.CollectionFactory;
import org.springframework.core.GenericCollectionTypeResolver;
import org.springframework.core.JdkVersion;
import org.springframework.core.MethodParameter;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

/**
 * Internal helper class for converting property values to target types.
 *
 * <p>Works on a given {@link PropertyEditorRegistrySupport} instance.
 * Used as a delegate by {@link BeanWrapperImpl} and {@link SimpleTypeConverter}.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 2.0
 * @see BeanWrapperImpl
 * @see SimpleTypeConverter
 */
class TypeConverterDelegate {

	private static final Log logger = LogFactory.getLog(TypeConverterDelegate.class);

	private static final Map unknownEditorTypes = Collections.synchronizedMap(new WeakHashMap());

	private final PropertyEditorRegistrySupport propertyEditorRegistry;

	private final Object targetObject;


	/**
	 * Create a new TypeConverterDelegate for the given editor registry.
	 * @param propertyEditorRegistry the editor registry to use
	 */
	public TypeConverterDelegate(PropertyEditorRegistrySupport propertyEditorRegistry) {
		this(propertyEditorRegistry, null);
	}

	/**
	 * Create a new TypeConverterDelegate for the given editor registry and bean instance.
	 * @param propertyEditorRegistry the editor registry to use
	 * @param targetObject the target object to work on (as context that can be passed to editors)
	 */
	public TypeConverterDelegate(PropertyEditorRegistrySupport propertyEditorRegistry, Object targetObject) {
		this.propertyEditorRegistry = propertyEditorRegistry;
		this.targetObject = targetObject;
	}


	/**
	 * Convert the value to the specified required type.
	 * @param newValue the proposed new value
	 * @param requiredType the type we must convert to
	 * (or <code>null</code> if not known, for example in case of a collection element)
	 * @return the new value, possibly the result of type conversion
	 * @throws IllegalArgumentException if type conversion failed
	 */
	public Object convertIfNecessary(Object newValue, Class requiredType) throws IllegalArgumentException {
		return convertIfNecessary(null, null, newValue, requiredType, null, null);
	}

	/**
	 * Convert the value to the specified required type.
	 * @param newValue the proposed new value
	 * @param requiredType the type we must convert to
	 * (or <code>null</code> if not known, for example in case of a collection element)
	 * @param methodParam the method parameter that is the target of the conversion
	 * (may be <code>null</code>)
	 * @return the new value, possibly the result of type conversion
	 * @throws IllegalArgumentException if type conversion failed
	 */
	public Object convertIfNecessary(Object newValue, Class requiredType, MethodParameter methodParam)
			throws IllegalArgumentException {

		return convertIfNecessary(null, null, newValue, requiredType, null, methodParam);
	}

	/**
	 * Convert the value to the required type for the specified property.
	 * @param propertyName name of the property
	 * @param oldValue the previous value, if available (may be <code>null</code>)
	 * @param newValue the proposed new value
	 * @param requiredType the type we must convert to
	 * (or <code>null</code> if not known, for example in case of a collection element)
	 * @return the new value, possibly the result of type conversion
	 * @throws IllegalArgumentException if type conversion failed
	 */
	public Object convertIfNecessary(
			String propertyName, Object oldValue, Object newValue, Class requiredType)
			throws IllegalArgumentException {

		return convertIfNecessary(propertyName, oldValue, newValue, requiredType, null, null);
	}

	/**
	 * Convert the value to the required type for the specified property.
	 * @param oldValue the previous value, if available (may be <code>null</code>)
	 * @param newValue the proposed new value
	 * @param descriptor the JavaBeans descriptor for the property
	 * @return the new value, possibly the result of type conversion
	 * @throws IllegalArgumentException if type conversion failed
	 */
	public Object convertIfNecessary(Object oldValue, Object newValue, PropertyDescriptor descriptor)
			throws IllegalArgumentException {

		return convertIfNecessary(
				descriptor.getName(), oldValue, newValue, descriptor.getPropertyType(), descriptor,
				new MethodParameter(descriptor.getWriteMethod(), 0));
	}


	/**
	 * Convert the value to the required type (if necessary from a String),
	 * for the specified property.
	 * @param propertyName name of the property
	 * @param oldValue the previous value, if available (may be <code>null</code>)
	 * @param newValue the proposed new value
	 * @param requiredType the type we must convert to
	 * (or <code>null</code> if not known, for example in case of a collection element)
	 * @param descriptor the JavaBeans descriptor for the property
	 * @param methodParam the method parameter that is the target of the conversion
	 * (may be <code>null</code>)
	 * @return the new value, possibly the result of type conversion
	 * @throws IllegalArgumentException if type conversion failed
	 */
	protected Object convertIfNecessary(
			String propertyName, Object oldValue, Object newValue, Class requiredType,
			PropertyDescriptor descriptor, MethodParameter methodParam)
			throws IllegalArgumentException {

		Object convertedValue = newValue;

		// Custom editor for this type?
		PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);

		// Value not of required type?
		if (editor != null || (requiredType != null && !ClassUtils.isAssignableValue(requiredType, convertedValue))) {
			if (editor == null && descriptor != null) {
				if (JdkVersion.isAtLeastJava15()) {
					editor = descriptor.createPropertyEditor(this.targetObject);
				}
				else {
					Class editorClass = descriptor.getPropertyEditorClass();
					if (editorClass != null) {
						editor = (PropertyEditor) BeanUtils.instantiateClass(editorClass);
					}
				}
			}
			if (editor == null && requiredType != null) {
				// No custom editor -> check BeanWrapperImpl's default editors.
				editor = (PropertyEditor) this.propertyEditorRegistry.getDefaultEditor(requiredType);
				if (editor == null && !unknownEditorTypes.containsKey(requiredType)) {
					// No BeanWrapper default editor -> check standard JavaBean editors.
					editor = PropertyEditorManager.findEditor(requiredType);
					if (editor == null) {
						unknownEditorTypes.put(requiredType, Boolean.TRUE);
					}
				}
			}
			convertedValue = doConvertValue(oldValue, convertedValue, requiredType, editor);
		}

		if (requiredType != null) {
			// Try to apply some standard type conversion rules if appropriate.

			if (convertedValue != null && requiredType.isArray()) {
				// Array required -> apply appropriate conversion of elements.
				return convertToTypedArray(convertedValue, propertyName, requiredType.getComponentType());
			}
			else if (convertedValue instanceof Collection && Collection.class.isAssignableFrom(requiredType)) {
				// Convert elements to target type, if determined.
				convertedValue = convertToTypedCollection((Collection) convertedValue, propertyName, methodParam);
			}
			else if (convertedValue instanceof Map && Map.class.isAssignableFrom(requiredType)) {
				// Convert keys and values to respective target type, if determined.
				convertedValue = convertToTypedMap((Map) convertedValue, propertyName, methodParam);
			}
			else if (convertedValue instanceof String && !requiredType.isInstance(convertedValue)) {
				if (JdkVersion.isAtLeastJava15() && requiredType.isEnum() && "".equals(convertedValue)) {
					// It's an empty enum identifier: reset the enum value to null.
					return null;
				}
				// Try field lookup as fallback: for JDK 1.5 enum or custom enum
				// with values defined as static fields. Resulting value still needs
				// to be checked, hence we don't return it right away.
				try {
					Field enumField = requiredType.getField((String) convertedValue);
					convertedValue = enumField.get(null);
				}
				catch (Throwable ex) {
					if (logger.isTraceEnabled()) {
						logger.trace("Field [" + convertedValue + "] isn't an enum value", ex);
					}
				}
			}

			if (!ClassUtils.isAssignableValue(requiredType, convertedValue)) {
				// Definitely doesn't match: throw IllegalArgumentException.
				throw new IllegalArgumentException("Cannot convert value of type [" +
						(newValue != null ? ClassUtils.getQualifiedName(newValue.getClass()) : null) +
						"] to required type [" + ClassUtils.getQualifiedName(requiredType) + "]" +
						(propertyName != null ? " for property '" + propertyName + "'" : "") +
						": no matching editors or conversion strategy found");
			}
		}

		return convertedValue;
	}

	/**
	 * Convert the value to the required type (if necessary from a String),
	 * using the given property editor.
	 * @param oldValue the previous value, if available (may be <code>null</code>)
	 * @param newValue the proposed new value
	 * @param requiredType the type we must convert to
	 * (or <code>null</code> if not known, for example in case of a collection element)