io.datakernel.http.HttpExceptionFormatter Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015-2018 SoftIndex LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.datakernel.http;

import org.intellij.lang.annotations.Language;
import org.jetbrains.annotations.NotNull;

import static io.datakernel.http.HttpHeaders.*;

/**
 * This is an interface for the formatter function for HTTP.
 * It converts unhandled checked exceptions that could be returned
 * from servers root servlet and transforms them into HTTP error responses.
 */
@FunctionalInterface
public interface HttpExceptionFormatter {
	@Language("HTML")
	String HTTP_ERROR_HTML =
			"" +
					"" +
					"" +
					"" +
					"Internal Server Error" +
					"" +
					"" +
					"" +
					"Internal Server Error" +
					"" +
					"{message}" +
					"" +
					"DataKernel 3.0.0" +
					"" +
					"";

	String INTERNAL_SERVER_ERROR_HTML = HTTP_ERROR_HTML.replaceAll("\\{message}
", "");

	@NotNull
	HttpResponse formatException(@NotNull Throwable e);

	/**
	 * Standard formatter maps all exceptions except HttpException to an empty response with 500 status code.
	 * HttpExceptions are mapped to a response with their status code, message and stacktrace of the cause if it was specified.
	 */
	HttpExceptionFormatter DEFAULT_FORMATTER = e -> {
		HttpResponse response;
		if (e instanceof HttpException) {
			int code = ((HttpException) e).getCode();
			response = HttpResponse.ofCode(code).withHtml(HTTP_ERROR_HTML.replaceAll("\\{message}", e.toString()));
		} else {
			response = HttpResponse.ofCode(500).withHtml(INTERNAL_SERVER_ERROR_HTML);
		}
		// default formatter leaks no information about unknown exceptions
		return response
				.withHeader(CACHE_CONTROL, "no-store")
				.withHeader(PRAGMA, "no-cache")
				.withHeader(AGE, "0");
	};

	/**
	 * This formatter prints the stacktrace of the exception into the HTTP response.
	 */
	HttpExceptionFormatter DEBUG_FORMATTER = e ->
			DebugStacktraceRenderer.render(e)
					.withHeader(CACHE_CONTROL, "no-store")
					.withHeader(PRAGMA, "no-cache")
					.withHeader(AGE, "0");

	/**
	 * This formatter if either one of {@link #DEFAULT_FORMATTER} or {@link #DEBUG_FORMATTER}, depending on whether
	 * the application was started from the IntelliJ IDE or not.
	 */
	HttpExceptionFormatter COMMON_FORMATTER =
			System.getProperty("java.class.path", "").contains("idea_rt.jar") ?
					DEBUG_FORMATTER :
					DEFAULT_FORMATTER;
}