UriComponentsBuilder Javadoc update

Closes gh-25604

Author: rstoyanchev

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

@@ -186,7 +186,13 @@ public static UriComponentsBuilder fromPath(String path) {
 	}
 
 	/**
-	 * Create a builder that is initialized with the given {@code URI}.
+	 * Create a builder that is initialized from the given {@code URI}.
+	 * <p><strong>Note:</strong> the components in the resulting builder will be
+	 * in fully encoded (raw) form and further changes must also supply values
+	 * that are fully encoded, for example via methods in {@link UriUtils}.
+	 * In addition please use {@link #build(boolean)} with a value of "true" to
+	 * build the {@link UriComponents} instance in order to indicate that the
+	 * components are encoded.
 	 * @param uri the URI to initialize with
 	 * @return the new {@code UriComponentsBuilder}
 	 */
@@ -387,11 +393,13 @@ public UriComponents build() {
 	}
 
 	/**
-	 * Build a {@code UriComponents} instance from the various components
-	 * contained in this builder.
-	 * @param encoded whether all the components set in this builder are
-	 * encoded ({@code true}) or not ({@code false})
+	 * Variant of {@link #build()} to create a {@link UriComponents} instance
+	 * when components are already fully encoded. This is useful for example if
+	 * the builder was created via {@link UriComponentsBuilder#fromUri(URI)}.
+	 * @param encoded whether the components in this builder are already encoded
 	 * @return the URI components
+	 * @throws IllegalArgumentException if any of the components contain illegal
+	 * characters that should have been encoded.
 	 */
 	public UriComponents build(boolean encoded) {
 		return buildInternal(encoded ?