Add PathEditor to enable conversion to java.nio.file.Path [SPR-14436]

[spring-projects-issues]

Holger Stenzhorn opened SPR-14436 and commented

Currently

@Value{some.path.property} private Path path;

fails with

Cannot convert value of type [java.lang.String] to required type [java.nio.file.Path]: no matching editors or conversion strategy found;

because no PathEditor is implemented (and added to the defaultEditors of PropertyEditorRegistrySupport).

It would be nice if this could be changed... :-) Below you can find a quick implementation for PathEditor:

/*
 * Copyright 2002-2016 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.propertyeditors;

import java.beans.PropertyEditorSupport;
import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;

import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceEditor;
import org.springframework.util.Assert;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;

/**
 * Editor for {@code java.nio.file.{@link Path}}, to directly populate a Path property
 * from a Spring resource location.
 *
 * <p>Supports Spring-style URL notation: any fully qualified standard URL
 * ("file:", "http:", etc) and Spring's special "classpath:" pseudo-URL.
 *
 * @author Juergen Hoeller
 * @author Thomas Risberg
 * @author Holger Stenzhorn
 * @since 06.07.2016
 * @see java.nio.file.Path
 * @see org.springframework.core.io.ResourceEditor
 * @see org.springframework.core.io.ResourceLoader
 * @see URLEditor
 * @see InputStreamEditor
 */
public class PathEditor extends PropertyEditorSupport {

	private final ResourceEditor resourceEditor;


	/**
	 * Create a new PathEditor,
	 * using the default ResourceEditor underneath.
	 */
	public PathEditor() {
		this.resourceEditor = new ResourceEditor();
	}

	/**
	 * Create a new PathEditor,
	 * using the given ResourceEditor underneath.
	 * @param resourceEditor the ResourceEditor to use
	 */
	public PathEditor(ResourceEditor resourceEditor) {
		Assert.notNull(resourceEditor, "ResourceEditor must not be null");
		this.resourceEditor = resourceEditor;
	}


	@Override
	public void setAsText(String text) throws IllegalArgumentException {
		if (!StringUtils.hasText(text)) {
			setValue(null);
			return;
		}

		// Check whether we got an absolute file path without "file:" prefix.
		// For backwards compatibility, we'll consider those as straight file path.
		if (!ResourceUtils.isUrl(text)) {
			Path path = Paths.get(text);
			if (path.isAbsolute()) {
				setValue(path);
				return;
			}
		}

		// Proceed with standard resource location parsing.
		this.resourceEditor.setAsText(text);
		Resource resource = (Resource) this.resourceEditor.getValue();

		// If it's a URL or a path pointing to an existing resource, use it as-is.
		if (ResourceUtils.isUrl(text) || resource.exists()) {
			try {
				setValue(resource.getFile().toPath());
			}
			catch (IOException ex) {
				throw new IllegalArgumentException(
						"Could not retrieve Path for " + resource + ": " + ex.getMessage());
			}
		}
		else {
			// Create a relative Path reference and hope for the best.
			setValue(Paths.get(text));
		}
	}

	@Override
	public String getAsText() {
		Path value = (Path) getValue();
		return (value != null ? value.toString() : "");
	}

}

---

Issue Links:

• Introduce java.nio.file.Path based Resource implementation [SPR-10608] #15237 Introduce java.nio.file.Path based Resource implementation
• PathEditor returns wrong result for absolute path in servletContext.getRealPath(...) [SPR-14549] #19117 PathEditor returns wrong result for absolute path in servletContext.getRealPath(...)

Referenced from: commits f85d48d, 23c2b6a

[spring-projects-issues]

Juergen Hoeller commented

I've added such a PathEditor, however, in a rather different style: not inheriting FileEditor's legacy with ambiguous plain paths but rather freshly based on Paths.get(URI)'s resolution algorithm, checking registered NIO file system providers, including the default file system for "file:..." paths. If that resolution fails, we try the Spring context's resource loader next, in particular for "classpath:..." pseudo-URLs and for context-relative resource locations.

Note that, in contrast to FileEditor, relative paths are only supported by Spring's resource abstraction here. Direct Paths.get resolution in a file system always has to go through the corresponding file system provider's scheme, i.e. "file" for the default file system.

[spring-projects-issues]

Holger Stenzhorn commented

Juergen Hoeller: Great! Thanks a lot for your quick support on this.