org.springframework.data.mapping.PersistentPropertyAccessor.java Source code

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Here is the source code for org.springframework.data.mapping.PersistentPropertyAccessor.java

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/*
 * Copyright 2014-2019 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.data.mapping;

import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Domain service to allow accessing and setting {@link PersistentProperty}s of an entity. Usually obtained through
 * {@link PersistentEntity#getPropertyAccessor(Object)}. In case type conversion shall be applied on property access,
 * use a {@link ConvertingPropertyAccessor}.
 * <p />
 * This service supports mutation for immutable classes by creating new object instances. These are managed as state of
 * {@link PersistentPropertyAccessor} and must be obtained from {@link #getBean()} after processing all updates.
 *
 * @author Oliver Gierke
 * @author Mark Paluch
 * @since 1.10
 * @see PersistentEntity#getPropertyAccessor(Object)
 * @see ConvertingPropertyAccessor
 */
public interface PersistentPropertyAccessor<T> {

    /**
     * Sets the given {@link PersistentProperty} to the given value. Will do type conversion if a
     * {@link org.springframework.core.convert.ConversionService} is configured.
     *
     * @param property must not be {@literal null}.
     * @param value can be {@literal null}.
     * @throws MappingException in case an exception occurred when setting the property value.
     */
    void setProperty(PersistentProperty<?> property, @Nullable Object value);

    /**
     * Sets the given value for the {@link PersistentProperty} pointed to by the given {@link PersistentPropertyPath}. The
     * lookup of intermediate values must not yield {@literal null}.
     *
     * @param path must not be {@literal null} or empty.
     * @param value can be {@literal null}.
     * @since 2.1
     */
    default void setProperty(PersistentPropertyPath<? extends PersistentProperty<?>> path, @Nullable Object value) {

        Assert.notNull(path, "PersistentPropertyPath must not be null!");
        Assert.isTrue(!path.isEmpty(), "PersistentPropertyPath must not be empty!");

        PersistentPropertyPath<? extends PersistentProperty<?>> parentPath = path.getParentPath();
        PersistentProperty<?> leafProperty = path.getRequiredLeafProperty();

        Object parent = parentPath.isEmpty() ? getBean() : getProperty(parentPath);

        if (parent == null) {

            String nullIntermediateMessage = "Cannot lookup property %s on null intermediate! Original path was: %s on %s.";

            throw new MappingException(String.format(nullIntermediateMessage, parentPath.getLeafProperty(),
                    path.toDotPath(), getBean().getClass().getName()));
        }

        PersistentPropertyAccessor<?> accessor = parent == getBean() //
                ? this //
                : leafProperty.getOwner().getPropertyAccessor(parent);

        accessor.setProperty(leafProperty, value);

        if (parentPath.isEmpty()) {
            return;
        }

        Object bean = accessor.getBean();

        if (bean != parent) {
            setProperty(parentPath, bean);
        }
    }

    /**
     * Returns the value of the given {@link PersistentProperty} of the underlying bean instance.
     *
     * @param property must not be {@literal null}.
     * @return can be {@literal null}.
     */
    @Nullable
    Object getProperty(PersistentProperty<?> property);

    /**
     * Return the value pointed to by the given {@link PersistentPropertyPath}. If the given path is empty, the wrapped
     * bean is returned.
     *
     * @param path must not be {@literal null}.
     * @return
     * @since 2.1
     */
    @Nullable
    default Object getProperty(PersistentPropertyPath<? extends PersistentProperty<?>> path) {
        return getProperty(path, new TraversalContext());
    }

    /**
     * Return the value pointed to by the given {@link PersistentPropertyPath}. If the given path is empty, the wrapped
     * bean is returned. On each path segment value lookup, the resulting value is post-processed by handlers registered
     * on the given {@link TraversalContext} context. This can be used to unwrap container types that are encountered
     * during the traversal.
     *
     * @param path must not be {@literal null}.
     * @param context must not be {@literal null}.
     * @return
     * @since 2.2
     */
    @Nullable
    default Object getProperty(PersistentPropertyPath<? extends PersistentProperty<?>> path,
            TraversalContext context) {

        Object bean = getBean();
        Object current = bean;

        if (path.isEmpty()) {
            return bean;
        }

        for (PersistentProperty<?> property : path) {

            if (current == null) {

                String nullIntermediateMessage = "Cannot lookup property %s on null intermediate! Original path was: %s on %s.";

                throw new MappingException(String.format(nullIntermediateMessage, property, path.toDotPath(),
                        bean.getClass().getName()));
            }

            PersistentEntity<?, ? extends PersistentProperty<?>> entity = property.getOwner();
            PersistentPropertyAccessor<Object> accessor = entity.getPropertyAccessor(current);

            current = context.postProcess(property, accessor.getProperty(property));
        }

        return current;
    }

    /**
     * Returns the underlying bean. The actual instance may change between
     * {@link #setProperty(PersistentProperty, Object)} calls.
     *
     * @return will never be {@literal null}.
     */
    T getBean();
}