Add IPv6 support in RestTemplate

Prior to this commit, RestTemplate would not would
not accept IPv6 raw addresses in URLs because UriComponentsBuilder
would not parse/encode the Host part correctly.

The UriComponentsBuilder now parses and encode raw IPv6 addresses
in the "[1abc:2abc:3abc::5ABC:6abc]" format and also supports the
use of IPv6 scope_ids (see JDK8 java.net.Inet6Address),
like "[1abc:2abc:3abc::5ABC:6abc%eth0]".

Issue: SPR-10539

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

@@ -182,7 +182,13 @@ final class HierarchicalUriComponents extends UriComponents {
 		}
 		String encodedScheme = encodeUriComponent(this.getScheme(), encoding, Type.SCHEME);
 		String encodedUserInfo = encodeUriComponent(this.userInfo, encoding, Type.USER_INFO);
-		String encodedHost = encodeUriComponent(this.host, encoding, Type.HOST);
+		String encodedHost;
+		if(StringUtils.hasLength(this.host) && this.host.startsWith("[")) {
+			encodedHost = encodeUriComponent(this.host, encoding, Type.HOST_IPV6);
+		} else {
+			encodedHost = encodeUriComponent(this.host, encoding, Type.HOST);
+		}
+
 		PathComponent encodedPath = this.path.encode(encoding);
 		MultiValueMap<String, String> encodedQueryParams =
 				new LinkedMultiValueMap<String, String>(this.queryParams.size());
@@ -468,6 +474,12 @@ final class HierarchicalUriComponents extends UriComponents {
 				return isUnreserved(c) || isSubDelimiter(c);
 			}
 		},
+		HOST_IPV6 {
+			@Override
+			public boolean isAllowed(int c) {
+				return isUnreserved(c) || isSubDelimiter(c) || '[' == c || ']' == c || ':' == c;
+			}
+		},
 		PORT {
 			@Override
 			public boolean isAllowed(int c) {

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

@@ -64,7 +64,11 @@ public class UriComponentsBuilder {
 
 	private static final String USERINFO_PATTERN = "([^@/]*)";
 
-	private static final String HOST_PATTERN = "([^/?#:]*)";
+	private static final String HOST_IPv4_PATTERN = "[^\\[/?#:]*";
+
+	private static final String HOST_IPV6_PATTERN = "\\[[\\p{XDigit}\\:\\.]*[%\\p{Alnum}]*\\]";
+
+	private static final String HOST_PATTERN = "("+HOST_IPV6_PATTERN + "|" + HOST_IPv4_PATTERN + ")";
 
 	private static final String PORT_PATTERN = "(\\d*)";
 
@@ -226,7 +230,11 @@ public class UriComponentsBuilder {
 			String scheme = m.group(1);
 			builder.scheme((scheme != null) ? scheme.toLowerCase() : scheme);
 			builder.userInfo(m.group(4));
-			builder.host(m.group(5));
+			String host = m.group(5);
+			if(StringUtils.hasLength(scheme) && !StringUtils.hasLength(host)) {
+				throw new IllegalArgumentException("[" + httpUrl + "] is not a valid HTTP URL");
+			}
+			builder.host(host);
 			String port = m.group(7);
 			if (StringUtils.hasLength(port)) {
 				builder.port(Integer.parseInt(port));

spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java

@@ -169,6 +169,31 @@ public class UriComponentsBuilderTests {
 		assertEquals("https", UriComponentsBuilder.fromHttpUrl("HTTPS://www.google.com").build().getScheme());
 	}
 
+	// SPR-10539
+
+	@Test(expected = IllegalArgumentException.class)
+	public void fromHttpUrlStringInvalidIPv6Host() throws URISyntaxException {
+		UriComponents result = UriComponentsBuilder
+				.fromHttpUrl("http://[1abc:2abc:3abc::5ABC:6abc:8080/resource").build().encode();
+	}
+
+	// SPR-10539
+
+	@Test
+	public void fromUriStringIPv6Host() throws URISyntaxException {
+	    UriComponents result = UriComponentsBuilder
+	            .fromUriString("http://[1abc:2abc:3abc::5ABC:6abc]:8080/resource").build().encode();
+	    assertEquals("[1abc:2abc:3abc::5ABC:6abc]",result.getHost());
+
+	    UriComponents resultWithScopeId = UriComponentsBuilder
+	            .fromUriString("http://[1abc:2abc:3abc::5ABC:6abc%eth0]:8080/resource").build().encode();
+	    assertEquals("[1abc:2abc:3abc::5ABC:6abc%25eth0]",resultWithScopeId.getHost());
+
+	    UriComponents resultIPv4compatible = UriComponentsBuilder
+			    .fromUriString("http://[::192.168.1.1]:8080/resource").build().encode();
+	    assertEquals("[::192.168.1.1]",resultIPv4compatible.getHost());
+	}
+
 	@Test
 	public void path() throws URISyntaxException {
 		UriComponentsBuilder builder = UriComponentsBuilder.fromPath("/foo/bar");