Add support for removing headers that match a Pattern

A new preprocessor method `removeMatchingHeaders` has been introduced
which takes one or more regular expression patterns (as Strings). Any
header that matches a pattern is removed.

Closes gh-195

docs/src/docs/asciidoc/customizing-requests-and-responses.adoc

@@ -105,6 +105,8 @@ different replacement can also be specified if you wish.
 `removeHeaders` on `Preprocessors` removes any occurrences of the named headers
 from the request or response.
 
+`removeMatchingHeaders` on `Preprocessors` applies the given patterns on every header and
+removes them when matching.
 
 
 [[customizing-requests-and-responses-preprocessors-replace-patterns]]

spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/HeaderRemovingOperationPreprocessor.java

@@ -19,6 +19,7 @@ package org.springframework.restdocs.operation.preprocess;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.regex.Pattern;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.restdocs.operation.OperationRequest;
@@ -27,20 +28,28 @@ import org.springframework.restdocs.operation.OperationResponse;
 import org.springframework.restdocs.operation.OperationResponseFactory;
 
 /**
- * An {@link OperationPreprocessor} that removes headers.
+ * An {@link OperationPreprocessor} that removes headers. The headers to remove are
+ * provided as constructor arguments and can be either plain string or patterns to match
+ * against the headers found
  *
  * @author Andy Wilkinson
  */
 class HeaderRemovingOperationPreprocessor implements OperationPreprocessor {
 
 	private final OperationRequestFactory requestFactory = new OperationRequestFactory();
-
 	private final OperationResponseFactory responseFactory = new OperationResponseFactory();
 
-	private final Set<String> headersToRemove;
+	private final Set<String> plainHeadersToRemove;
+	private final Set<Pattern> patternHeadersToRemove;
 
-	HeaderRemovingOperationPreprocessor(String... headersToRemove) {
-		this.headersToRemove = new HashSet<>(Arrays.asList(headersToRemove));
+	HeaderRemovingOperationPreprocessor(String ... headersToRemove) {
+		this.plainHeadersToRemove = new HashSet<>(Arrays.asList(headersToRemove));
+		this.patternHeadersToRemove = null;
+	}
+
+	HeaderRemovingOperationPreprocessor(Pattern ... patternHeadersToRemove) {
+		this.plainHeadersToRemove = null;
+		this.patternHeadersToRemove = new HashSet<>(Arrays.asList(patternHeadersToRemove));
 	}
 
 	@Override
@@ -58,8 +67,25 @@ class HeaderRemovingOperationPreprocessor implements OperationPreprocessor {
 	private HttpHeaders removeHeaders(HttpHeaders originalHeaders) {
 		HttpHeaders processedHeaders = new HttpHeaders();
 		processedHeaders.putAll(originalHeaders);
-		for (String headerToRemove : this.headersToRemove) {
-			processedHeaders.remove(headerToRemove);
+		if (this.plainHeadersToRemove != null) {
+			for (String headerToRemove : this.plainHeadersToRemove) {
+				processedHeaders.remove(headerToRemove);
+			}
+		}
+		else {
+			Set<String> toRemove = new HashSet<>();
+			for (String headerToCheck : originalHeaders.keySet()) {
+				for (Pattern pattern : this.patternHeadersToRemove) {
+					if (pattern.matcher(headerToCheck).matches()) {
+						toRemove.add(headerToCheck);
+					}
+				}
+			}
+			// Remove afterwards to avoid side effects when removing while iterating over
+			// the set keys :
+			for (String headerToRemove : toRemove) {
+				processedHeaders.remove(headerToRemove);
+			}
 		}
 		return processedHeaders;
 	}

spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/Preprocessors.java

@@ -76,13 +76,28 @@ public final class Preprocessors {
 	 * Returns an {@code OperationPreprocessor} that will remove headers from the request
 	 * or response.
 	 *
-	 * @param headersToRemove the names of the headers to remove
+	 * @param headersToRemove the names of the headers to remove.
 	 * @return the preprocessor
 	 */
 	public static OperationPreprocessor removeHeaders(String... headersToRemove) {
 		return new HeaderRemovingOperationPreprocessor(headersToRemove);
 	}
 
+	/**
+	 * Returns an {@code OperationPreprocessor} that will remove headers from the request
+	 * or response based on a pattern match.
+	 *
+	 * @param headerPatternsToRemove pattern for the header names to remove. Every matchig header will be removed.
+	 * @return the preprocessor
+	 */
+	public static OperationPreprocessor removeMatchingHeaders(String... headerPatternsToRemove) {
+		Pattern[] patterns = new Pattern[headerPatternsToRemove.length];
+		for (int i = 0; i < headerPatternsToRemove.length; i++) {
+			patterns[i] = Pattern.compile(headerPatternsToRemove[i]);
+		}
+		return new HeaderRemovingOperationPreprocessor(patterns);
+	}
+
 	/**
 	 * Returns an {@code OperationPreprocessor} that will mask the href of hypermedia
 	 * links in the request or response.

spring-restdocs-core/src/test/java/org/springframework/restdocs/operation/preprocess/HeaderRemovingOperationPreprocessorTests.java

@@ -19,6 +19,7 @@ package org.springframework.restdocs.operation.preprocess;
 import java.net.URI;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.regex.Pattern;
 
 import org.junit.Test;
 import org.springframework.http.HttpHeaders;
@@ -66,18 +67,43 @@ public class HeaderRemovingOperationPreprocessorTests {
 
 	@Test
 	public void modifyResponseHeaders() {
-		OperationResponse response = this.responseFactory.create(HttpStatus.OK,
-				getHttpHeaders(), new byte[0]);
+		OperationResponse response = createResponse();
 		OperationResponse preprocessed = this.preprocessor.preprocess(response);
 		assertThat(preprocessed.getHeaders().size(), is(equalTo(1)));
 		assertThat(preprocessed.getHeaders(), hasEntry("a", Arrays.asList("alpha")));
 	}
 
-	private HttpHeaders getHttpHeaders() {
+	@Test
+	public void modifyWithPattern() {
+		OperationResponse response = createResponse("content-length", "1234");
+		HeaderRemovingOperationPreprocessor processor =
+			new HeaderRemovingOperationPreprocessor(Pattern.compile("co.*le(.)gth]"));
+		OperationResponse preprocessed = processor.preprocess(response);
+		assertThat(preprocessed.getHeaders().size(), is(equalTo(2)));
+		assertThat(preprocessed.getHeaders(), hasEntry("a", Arrays.asList("alpha")));
+		assertThat(preprocessed.getHeaders(), hasEntry("b", Arrays.asList("bravo", "banana")));
+	}
+
+	@Test
+	public void removeAllHeaders() {
+		HeaderRemovingOperationPreprocessor processor =
+			new HeaderRemovingOperationPreprocessor(Pattern.compile(".*"));
+		OperationResponse preprocessed = processor.preprocess(createResponse());
+		assertThat(preprocessed.getHeaders().size(), is(equalTo(0)));
+	}
+
+	private OperationResponse createResponse(String ... extraHeaders) {
+		return this.responseFactory.create(HttpStatus.OK, getHttpHeaders(extraHeaders), new byte[0]);
+	}
+
+	private HttpHeaders getHttpHeaders(String ... extraHeaders) {
 		HttpHeaders httpHeaders = new HttpHeaders();
 		httpHeaders.add("a", "alpha");
 		httpHeaders.add("b", "bravo");
 		httpHeaders.add("b", "banana");
+		for (int i = 0; i < extraHeaders.length; i += 2) {
+			httpHeaders.add(extraHeaders[i], extraHeaders[i + 1]);
+		}
 		return httpHeaders;
 	}