Support {/...} patterns in UriComponents(Builder)

This commit introduces support for "Path Segment URI Variable
expansion", see https://tools.ietf.org/html/rfc6570#section-3.2.6.
In practice, this means that URI template variables prefixed with a '/'
are treated like path segments and - as such - will encode any '/'
found. For example: {/foo} expanded with "bar/baz" with result in
"bar%2F".

Issue: SPR-12750

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -22,11 +22,11 @@ import java.io.UnsupportedEncodingException;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.regex.Pattern;
 
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -631,12 +631,26 @@ final class HierarchicalUriComponents extends UriComponents {
 	 */
 	static final class FullPathComponent implements PathComponent {
 
+		// Pattern used to split the path into segments: '/' if not preceded by '{',
+		// using negative look-behind
+		private static final Pattern DELIMITER_PATTERN = Pattern.compile("(?<!\\{)/");
+
+
+		private final List<PartialPath> partialPaths;
+
 		private final String path;
 
+
 		public FullPathComponent(String path) {
+			this.partialPaths = PartialPath.parse(path);
 			this.path = path;
 		}
 
+		private FullPathComponent(List<PartialPath> partialPaths) {
+			this.partialPaths = partialPaths;
+			this.path = PartialPath.getPath(partialPaths);
+		}
+
 		@Override
 		public String getPath() {
 			return this.path;
@@ -644,25 +658,32 @@ final class HierarchicalUriComponents extends UriComponents {
 
 		@Override
 		public List<String> getPathSegments() {
-			String delimiter = new String(new char[]{PATH_DELIMITER});
-			String[] pathSegments = StringUtils.tokenizeToStringArray(path, delimiter);
-			return Collections.unmodifiableList(Arrays.asList(pathSegments));
+			String[] pathSegments = DELIMITER_PATTERN.split(getPath());
+			List<String> result = new ArrayList<String>(pathSegments.length);
+			for (String pathSegment : pathSegments) {
+				if (StringUtils.hasLength(pathSegment)) {
+					result.add(pathSegment);
+				}
+			}
+			return Collections.unmodifiableList(result);
 		}
 
 		@Override
 		public PathComponent encode(String encoding) throws UnsupportedEncodingException {
-			String encodedPath = encodeUriComponent(getPath(),encoding, Type.PATH);
+			List<PartialPath> encodedPath =
+					PartialPath.encode(this.partialPaths, encoding);
 			return new FullPathComponent(encodedPath);
 		}
 
 		@Override
 		public void verify() {
-			verifyUriComponent(this.path, Type.PATH);
+			verifyUriComponent(getPath(), Type.PATH);
 		}
 
 		@Override
 		public PathComponent expand(UriTemplateVariables uriVariables) {
-			String expandedPath = expandUriComponent(getPath(), uriVariables);
+			List<PartialPath> expandedPath =
+					PartialPath.expand(this.partialPaths, uriVariables);
 			return new FullPathComponent(expandedPath);
 		}
 
@@ -681,6 +702,97 @@ final class HierarchicalUriComponents extends UriComponents {
 		public int hashCode() {
 			return getPath().hashCode();
 		}
+
+		/**
+		 * Represents a part of the full path, with a separate encoding type.
+		 * Required because of {/...} uri variables, which need to encoded as PATH_SEGMENT
+		 * rather than PATH.
+		 */
+		static final class PartialPath implements Serializable {
+
+			final String value;
+
+			final Type type;
+
+			private PartialPath(String value, Type type) {
+				Assert.hasLength(value);
+				Assert.isTrue(Type.PATH == type || Type.PATH_SEGMENT == type);
+				this.value = value;
+				this.type = type;
+			}
+
+			private PartialPath expand(UriTemplateVariables uriVariables) {
+				String expandedValue = expandUriComponent(this.value, uriVariables);
+				return new PartialPath(expandedValue, this.type);
+			}
+
+			private PartialPath encode(String encoding)
+					throws UnsupportedEncodingException {
+				String encodedPath = encodeUriComponent(this.value, encoding, this.type);
+				return new PartialPath(encodedPath, this.type);
+			}
+
+			@Override
+			public String toString() {
+				return value;
+			}
+
+			public static List<PartialPath> parse(String path) {
+				List<PartialPath> result = new ArrayList<PartialPath>();
+				int startIdx;
+				int endIdx = 0;
+				while ((startIdx = path.indexOf("{/", endIdx)) != -1) {
+					if (startIdx > endIdx) {
+						String prevPart = path.substring(endIdx, startIdx);
+						result.add(new PartialPath(prevPart, Type.PATH));
+					}
+					endIdx = path.indexOf('}', startIdx + 2) + 1;
+					if (endIdx == -1) {
+						throw new IllegalArgumentException("Path \"" + path + "\" has no " +
+								"closing \"}\" after \"{/\" at index " + startIdx);
+					}
+					String part = path.substring(startIdx, endIdx);
+					result.add(new PartialPath(part, Type.PATH_SEGMENT));
+				}
+				if (endIdx < path.length()) {
+					String endPart = path.substring(endIdx);
+					result.add(new PartialPath(endPart, Type.PATH));
+				}
+				return Collections.unmodifiableList(result);
+			}
+
+			public static String getPath(List<PartialPath> partialPaths) {
+				StringBuilder builder = new StringBuilder();
+				for (PartialPath partialPath : partialPaths) {
+					builder.append(partialPath.value);
+				}
+				return builder.toString();
+			}
+
+			public static List<PartialPath> expand(
+					List<PartialPath> partialPaths,
+					UriTemplateVariables uriVariables) {
+				List<PartialPath> result = new ArrayList<PartialPath>();
+				for (PartialPath partialPath : partialPaths) {
+					PartialPath expanded = partialPath.expand(uriVariables);
+					result.add(expanded);
+				}
+				return result;
+			}
+
+			public static List<PartialPath> encode(
+					List<PartialPath> partialPaths, String encoding)
+					throws UnsupportedEncodingException {
+				List<PartialPath> result = new ArrayList<PartialPath>();
+				for (PartialPath partialPath : partialPaths) {
+					PartialPath encoded = partialPath.encode(encoding);
+					result.add(encoded);
+				}
+				return result;
+			}
+
+		}
+
 	}
 
 

spring-web/src/main/java/org/springframework/web/util/UriComponents.java

@@ -45,7 +45,7 @@ public abstract class UriComponents implements Serializable {
 	private static final String DEFAULT_ENCODING = "UTF-8";
 
 	/** Captures URI template variable names. */
-	private static final Pattern NAMES_PATTERN = Pattern.compile("\\{([^/]+?)\\}");
+	private static final Pattern NAMES_PATTERN = Pattern.compile("\\{(/?[^/]+?)\\}");
 
 
 	private final String scheme;
@@ -237,6 +237,9 @@ public abstract class UriComponents implements Serializable {
 	}
 
 	private static String getVariableName(String match) {
+		if (match.length() > 0 && match.charAt(0) == '/') {
+			match = match.substring(1);
+		}
 		int colonIdx = match.indexOf(':');
 		return (colonIdx != -1 ? match.substring(0, colonIdx) : match);
 	}