Error details in RestTemplate client and server exceptions

spring-web/src/main/java/org/springframework/web/client/DefaultHttpErrorDetailsExtractor.java

@@ -0,0 +1,138 @@
+package org.springframework.web.client;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.net.URI;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
+import org.jetbrains.annotations.NotNull;
+import org.springframework.http.HttpMethod;
+import org.springframework.lang.Nullable;
+
+/**
+ * Spring's default implementation of the {@link HttpErrorDetailsExtractor} interface.
+ *
+ * <p>This extractor will compose a short summary of the http error response, including:
+ * <ul>
+ *     <li>request URI
+ *     <li>request method
+ *     <li>a 200-character preview of the response body, unformatted
+ * </ul>
+ *
+ * An example:
+ * <pre>
+ * 404 Not Found after GET http://example.com:8080/my-endpoint : [{'id': 123, 'message': 'my very long... (500 bytes)]</code>
+ * </pre>
+ *
+ * @author Jerzy Krolak
+ * @since 5.1
+ * @see DefaultResponseErrorHandler#setHttpErrorDetailsExtractor(HttpErrorDetailsExtractor)
+ */
+public class DefaultHttpErrorDetailsExtractor implements HttpErrorDetailsExtractor {
+
+	private static final int MAX_BODY_BYTES_LENGTH = 400;
+
+	private static final int MAX_BODY_CHARS_LENGTH = 200;
+
+	/**
+	 * Assemble a short summary of the HTTP error response.
+	 * @param rawStatusCode HTTP status code
+	 * @param statusText HTTP status text
+	 * @param responseBody response body
+	 * @param responseCharset response charset
+	 * @param url request URI
+	 * @param method request method
+	 * @return error details string. Example: <pre>404 Not Found after GET http://example.com:8080/my-endpoint : [{'id': 123, 'message': 'my very long... (500 bytes)]</code></pre>
+	 */
+	@Override
+	@NotNull
+	public String getErrorDetails(int rawStatusCode, String statusText, @Nullable byte[] responseBody,
+			@Nullable Charset responseCharset, @Nullable URI url, @Nullable HttpMethod method) {
+
+		if (url == null || method == null) {
+			return getSimpleErrorDetails(rawStatusCode, statusText);
+		}
+
+		return getCompleteErrorDetails(rawStatusCode, statusText, responseBody, responseCharset, url, method);
+	}
+
+	@NotNull
+	private String getCompleteErrorDetails(int rawStatusCode, String statusText, @Nullable byte[] responseBody,
+			@Nullable Charset responseCharset, @Nullable URI url, @Nullable HttpMethod method) {
+
+		StringBuilder result = new StringBuilder();
+
+		result.append(getSimpleErrorDetails(rawStatusCode, statusText))
+				.append(" after ")
+				.append(method)
+				.append(" ")
+				.append(url)
+				.append(" : ");
+
+		if (responseBody == null || responseBody.length == 0) {
+			result.append("[no body]");
+		}
+		else {
+			result
+					.append("[")
+					.append(getResponseBody(responseBody, responseCharset))
+					.append("]");
+		}
+
+		return result.toString();
+	}
+
+	@NotNull
+	private String getSimpleErrorDetails(int rawStatusCode, String statusText) {
+		return rawStatusCode + " " + statusText;
+	}
+
+	private String getResponseBody(byte[] responseBody, @Nullable Charset responseCharset) {
+		Charset charset = getCharsetOrDefault(responseCharset);
+		if (responseBody.length < MAX_BODY_BYTES_LENGTH) {
+			return getCompleteResponseBody(responseBody, charset);
+		}
+		return getResponseBodyPreview(responseBody, charset);
+	}
+
+	@NotNull
+	private String getCompleteResponseBody(byte[] responseBody, Charset responseCharset) {
+		return new String(responseBody, responseCharset);
+	}
+
+	private String getResponseBodyPreview(byte[] responseBody, Charset responseCharset) {
+		try {
+			String bodyPreview = readBodyAsString(responseBody, responseCharset);
+			return bodyPreview + "... (" + responseBody.length + " bytes)";
+		}
+		catch (IOException e) {
+			// should never happen
+			throw new IllegalStateException(e);
+		}
+	}
+
+	@NotNull
+	private String readBodyAsString(byte[] responseBody, Charset responseCharset) throws IOException {
+
+		Reader reader = new InputStreamReader(new ByteArrayInputStream(responseBody), responseCharset);
+		CharBuffer result = CharBuffer.allocate(MAX_BODY_CHARS_LENGTH);
+
+		reader.read(result);
+		reader.close();
+		result.flip();
+
+		return result.toString();
+	}
+
+	private Charset getCharsetOrDefault(@Nullable Charset responseCharset) {
+		if (responseCharset == null) {
+			return StandardCharsets.ISO_8859_1;
+		}
+		return responseCharset;
+	}
+
+}

spring-web/src/main/java/org/springframework/web/client/DefaultResponseErrorHandler.java

@@ -17,13 +17,16 @@
 package org.springframework.web.client;
 
 import java.io.IOException;
+import java.net.URI;
 import java.nio.charset.Charset;
 
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.ClientHttpResponse;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
 
 /**
@@ -43,6 +46,17 @@
  */
 public class DefaultResponseErrorHandler implements ResponseErrorHandler {
 
+	private HttpErrorDetailsExtractor httpErrorDetailsExtractor = new DefaultHttpErrorDetailsExtractor();
+
+	/**
+	 * Set the error summary extractor.
+	 * <p>By default, DefaultResponseErrorHandler uses a {@link DefaultHttpErrorDetailsExtractor}.
+	 */
+	public void setHttpErrorDetailsExtractor(HttpErrorDetailsExtractor httpErrorDetailsExtractor) {
+		Assert.notNull(httpErrorDetailsExtractor, "HttpErrorDetailsExtractor must not be null");
+		this.httpErrorDetailsExtractor = httpErrorDetailsExtractor;
+	}
+
 	/**
 	 * Delegates to {@link #hasError(HttpStatus)} (for a standard status enum value) or
 	 * {@link #hasError(int)} (for an unknown status code) with the response status code.
@@ -87,19 +101,31 @@ protected boolean hasError(int unknownStatusCode) {
 	}
 
 	/**
-	 * Delegates to {@link #handleError(ClientHttpResponse, HttpStatus)} with the
+	 * Delegates to {@link #handleError(URI, HttpMethod, ClientHttpResponse, HttpStatus)} with the
 	 * response status code.
 	 * @throws UnknownHttpStatusCodeException in case of an unresolvable status code
-	 * @see #handleError(ClientHttpResponse, HttpStatus)
+	 * @see #handleError(URI, HttpMethod, ClientHttpResponse, HttpStatus)
 	 */
 	@Override
 	public void handleError(ClientHttpResponse response) throws IOException {
+		handleError(null, null, response);
+	}
+
+	/**
+	 * Delegates to {@link #handleError(URI, HttpMethod, ClientHttpResponse, HttpStatus)} with the
+	 * response status code.
+	 * @throws UnknownHttpStatusCodeException in case of an unresolvable status code
+	 * @see #handleError(URI, HttpMethod, ClientHttpResponse, HttpStatus)
+	 */
+	@Override
+	public void handleError(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
 		HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
 		if (statusCode == null) {
-			throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(),
-					response.getHeaders(), getResponseBody(response), getCharset(response));
+			String message = httpErrorDetailsExtractor.getErrorDetails(response.getRawStatusCode(), response.getStatusText(), getResponseBody(response), getCharset(response), url, method);
+			throw new UnknownHttpStatusCodeException(message, response.getRawStatusCode(), response.getStatusText(),
+					response.getHeaders(), getResponseBody(response), getCharset(response), url, method);
 		}
-		handleError(response, statusCode);
+		handleError(url, method, response, statusCode);
 	}
 
 	/**
@@ -114,17 +140,34 @@ public void handleError(ClientHttpResponse response) throws IOException {
 	 * @see HttpServerErrorException#create
 	 */
 	protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
+		handleError(null, null, response, statusCode);
+	}
+
+	/**
+	 * Handle the error in the given response with the given resolved status code.
+	 * <p>This default implementation throws a {@link HttpClientErrorException} if the response status code
+	 * is {@link org.springframework.http.HttpStatus.Series#CLIENT_ERROR}, a {@link HttpServerErrorException}
+	 * if it is {@link org.springframework.http.HttpStatus.Series#SERVER_ERROR},
+	 * and a {@link RestClientException} in other cases.
+	 * @since 5.0
+	 */
+	protected void handleError(@Nullable URI url, @Nullable HttpMethod method, ClientHttpResponse response,
+			HttpStatus statusCode) throws IOException {
+
 		String statusText = response.getStatusText();
 		HttpHeaders headers = response.getHeaders();
 		byte[] body = getResponseBody(response);
 		Charset charset = getCharset(response);
+		String message = httpErrorDetailsExtractor.getErrorDetails(statusCode.value(), statusText, body, charset, url, method);
+
 		switch (statusCode.series()) {
 			case CLIENT_ERROR:
-				throw HttpClientErrorException.create(statusCode, statusText, headers, body, charset);
+				throw HttpClientErrorException.create(message, statusCode, statusText, headers, body, charset, url, method);
 			case SERVER_ERROR:
-				throw HttpServerErrorException.create(statusCode, statusText, headers, body, charset);
+				throw HttpServerErrorException.create(message, statusCode, statusText, headers, body, charset, url, method);
 			default:
-				throw new UnknownHttpStatusCodeException(statusCode.value(), statusText, headers, body, charset);
+				throw new UnknownHttpStatusCodeException(message, statusCode.value(), statusText, headers, body,
+						charset, url, method);
 		}
 	}