Allow HttpTrace instances to be created

Previously, the API required to create HttpTrace instances was
package-private. This made it difficult to implement an
HttpTraceRepository that persists the HttpTrace instances
rather than holding them in memory as it inhibited recreation of the
instances when they read from the persistent store.

This commit adds public constructors to HttpTrace and related classes
to enable recreation of an HttpTrace. The package-private methods for
mutating properties have not been made public to ensure that the
public API remains immutable.

Closes gh-14726

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/trace/http/HttpTrace.java

@@ -18,6 +18,7 @@ package org.springframework.boot.actuate.trace.http;
 
 import java.net.URI;
 import java.time.Instant;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -33,7 +34,7 @@ import org.springframework.util.StringUtils;
  */
 public final class HttpTrace {
 
-	private final Instant timestamp = Instant.now();
+	private final Instant timestamp;
 
 	private volatile Principal principal;
 
@@ -45,8 +46,32 @@ public final class HttpTrace {
 
 	private volatile Long timeTaken;
 
+	/**
+	 * Creates a fully-configured {@code HttpTrace} instance. Primarly for use by
+	 * {@link HttpTraceRepository} implementations when recreating a trace from a
+	 * persistent store.
+	 * @param request the request
+	 * @param response the response
+	 * @param timestamp the timestamp of the request-response exchange
+	 * @param principal the principal, if any
+	 * @param session the session, if any
+	 * @param timeTaken the time taken, in milliseconds, to complete the request-response
+	 * exchange, if known
+	 * @since 2.1.0
+	 */
+	public HttpTrace(Request request, Response response, Instant timestamp,
+			Principal principal, Session session, Long timeTaken) {
+		this.request = request;
+		this.response = response;
+		this.timestamp = timestamp;
+		this.principal = principal;
+		this.session = session;
+		this.timeTaken = timeTaken;
+	}
+
 	HttpTrace(TraceableRequest request) {
 		this.request = new Request(request);
+		this.timestamp = Instant.now();
 	}
 
 	public Instant getTimestamp() {
@@ -107,10 +132,26 @@ public final class HttpTrace {
 		private final String remoteAddress;
 
 		private Request(TraceableRequest request) {
-			this.method = request.getMethod();
-			this.uri = request.getUri();
-			this.headers = request.getHeaders();
-			this.remoteAddress = request.getRemoteAddress();
+			this(request.getMethod(), request.getUri(), request.getHeaders(),
+					request.getRemoteAddress());
+		}
+
+		/**
+		 * Creates a fully-configured {@code Request} instance. Primarly for use by
+		 * {@link HttpTraceRepository} implementations when recreating a request from a
+		 * persistent store.
+		 * @param method the HTTP method of the request
+		 * @param uri the URI of the request
+		 * @param headers the request headers
+		 * @param remoteAddress remote address from which the request was sent, if known
+		 * @since 2.1.0
+		 */
+		public Request(String method, URI uri, Map<String, List<String>> headers,
+				String remoteAddress) {
+			this.method = method;
+			this.uri = uri;
+			this.headers = new LinkedHashMap<>(headers);
+			this.remoteAddress = remoteAddress;
 		}
 
 		public String getMethod() {
@@ -141,8 +182,20 @@ public final class HttpTrace {
 		private final Map<String, List<String>> headers;
 
 		Response(TraceableResponse response) {
-			this.status = response.getStatus();
-			this.headers = response.getHeaders();
+			this(response.getStatus(), response.getHeaders());
+		}
+
+		/**
+		 * Creates a fully-configured {@code Response} instance. Primarly for use by
+		 * {@link HttpTraceRepository} implementations when recreating a response from a
+		 * persistent store.
+		 * @param status the status of the response
+		 * @param headers the response headers
+		 * @since 2.1.0
+		 */
+		public Response(int status, Map<String, List<String>> headers) {
+			this.status = status;
+			this.headers = new LinkedHashMap<>(headers);
 		}
 
 		public int getStatus() {
@@ -162,7 +215,12 @@ public final class HttpTrace {
 
 		private final String id;
 
-		private Session(String id) {
+		/**
+		 * Creates a {@code Session}.
+		 * @param id the session id
+		 * @since 2.1.0
+		 */
+		public Session(String id) {
 			this.id = id;
 		}
 
@@ -179,7 +237,12 @@ public final class HttpTrace {
 
 		private final String name;
 
-		private Principal(String name) {
+		/**
+		 * Creates a {@code Principal}.
+		 * @param name the name of the principal
+		 * @since 2.1.0
+		 */
+		public Principal(String name) {
 			this.name = name;
 		}