Java tutorial
/* * Copyright 2002-2018 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 * * https://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.lang.reflect.Field; import java.util.HashMap; import java.util.Map; import org.springframework.core.ResolvableType; import org.springframework.core.convert.TypeDescriptor; import org.springframework.lang.Nullable; import org.springframework.util.ReflectionUtils; /** * {@link ConfigurablePropertyAccessor} implementation that directly accesses * instance fields. Allows for direct binding to fields instead of going through * JavaBean setters. * * <p>As of Spring 4.2, the vast majority of the {@link BeanWrapper} features have * been merged to {@link AbstractPropertyAccessor}, which means that property * traversal as well as collections and map access is now supported here as well. * * <p>A DirectFieldAccessor's default for the "extractOldValueForEditor" setting * is "true", since a field can always be read without side effects. * * @author Juergen Hoeller * @author Stephane Nicoll * @since 2.0 * @see #setExtractOldValueForEditor * @see BeanWrapper * @see org.springframework.validation.DirectFieldBindingResult * @see org.springframework.validation.DataBinder#initDirectFieldAccess() */ public class DirectFieldAccessor extends AbstractNestablePropertyAccessor { private final Map<String, FieldPropertyHandler> fieldMap = new HashMap<>(); /** * Create a new DirectFieldAccessor for the given object. * @param object object wrapped by this DirectFieldAccessor */ public DirectFieldAccessor(Object object) { super(object); } /** * Create a new DirectFieldAccessor for the given object, * registering a nested path that the object is in. * @param object object wrapped by this DirectFieldAccessor * @param nestedPath the nested path of the object * @param parent the containing DirectFieldAccessor (must not be {@code null}) */ protected DirectFieldAccessor(Object object, String nestedPath, DirectFieldAccessor parent) { super(object, nestedPath, parent); } @Override @Nullable protected FieldPropertyHandler getLocalPropertyHandler(String propertyName) { FieldPropertyHandler propertyHandler = this.fieldMap.get(propertyName); if (propertyHandler == null) { Field field = ReflectionUtils.findField(getWrappedClass(), propertyName); if (field != null) { propertyHandler = new FieldPropertyHandler(field); this.fieldMap.put(propertyName, propertyHandler); } } return propertyHandler; } @Override protected DirectFieldAccessor newNestedPropertyAccessor(Object object, String nestedPath) { return new DirectFieldAccessor(object, nestedPath, this); } @Override protected NotWritablePropertyException createNotWritablePropertyException(String propertyName) { PropertyMatches matches = PropertyMatches.forField(propertyName, getRootClass()); throw new NotWritablePropertyException(getRootClass(), getNestedPath() + propertyName, matches.buildErrorMessage(), matches.getPossibleMatches()); } private class FieldPropertyHandler extends PropertyHandler { private final Field field; public FieldPropertyHandler(Field field) { super(field.getType(), true, true); this.field = field; } @Override public TypeDescriptor toTypeDescriptor() { return new TypeDescriptor(this.field); } @Override public ResolvableType getResolvableType() { return ResolvableType.forField(this.field); } @Override @Nullable public TypeDescriptor nested(int level) { return TypeDescriptor.nested(this.field, level); } @Override @Nullable public Object getValue() throws Exception { try { ReflectionUtils.makeAccessible(this.field); return this.field.get(getWrappedInstance()); } catch (IllegalAccessException ex) { throw new InvalidPropertyException(getWrappedClass(), this.field.getName(), "Field is not accessible", ex); } } @Override public void setValue(@Nullable Object value) throws Exception { try { ReflectionUtils.makeAccessible(this.field); this.field.set(getWrappedInstance(), value); } catch (IllegalAccessException ex) { throw new InvalidPropertyException(getWrappedClass(), this.field.getName(), "Field is not accessible", ex); } } } }