Java tutorial
/* * Copyright 2002-2019 the original author or authors. * * 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 * * https://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 org.springframework.integration.http.outbound; import java.net.URI; import java.util.List; import java.util.function.Supplier; import org.springframework.core.ParameterizedTypeReference; import org.springframework.expression.Expression; import org.springframework.expression.common.LiteralExpression; import org.springframework.http.HttpEntity; import org.springframework.http.HttpMethod; import org.springframework.http.ResponseEntity; import org.springframework.http.client.ClientHttpRequestFactory; import org.springframework.http.converter.HttpMessageConverter; import org.springframework.integration.expression.ValueExpression; import org.springframework.messaging.Message; import org.springframework.messaging.MessageHandlingException; import org.springframework.util.Assert; import org.springframework.web.client.ResponseErrorHandler; import org.springframework.web.client.RestClientException; import org.springframework.web.client.RestTemplate; /** * A {@link org.springframework.messaging.MessageHandler} * implementation that executes HTTP requests by delegating * to a {@link RestTemplate} instance. If the 'expectReply' flag is set to true (the default) * then a reply Message will be generated from the HTTP response. If that response contains * a body, it will be used as the reply Message's payload. Otherwise the reply Message's * payload will contain the response status as an instance of the * {@link org.springframework.http.HttpStatus} enum. * When there is a response body, the {@link org.springframework.http.HttpStatus} enum * instance will instead be * copied to the MessageHeaders of the reply. In both cases, the response headers will * be mapped to the reply Message's headers by this handler's * {@link org.springframework.integration.mapping.HeaderMapper} instance. * * @author Mark Fisher * @author Oleg Zhurakousky * @author Gary Russell * @author Gunnar Hillert * @author Artem Bilan * @author Wallace Wadge * @author Shiliang Li * * @since 2.0 */ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecutingMessageHandler { private final RestTemplate restTemplate; /** * Create a handler that will send requests to the provided URI. * @param uri The URI. */ public HttpRequestExecutingMessageHandler(URI uri) { this(new ValueExpression<>(uri)); } /** * Create a handler that will send requests to the provided URI. * @param uri The URI. */ public HttpRequestExecutingMessageHandler(String uri) { this(uri, null); } /** * Create a handler that will send requests to the provided URI Expression. * @param uriExpression The URI expression. */ public HttpRequestExecutingMessageHandler(Expression uriExpression) { this(uriExpression, null); } /** * Create a handler that will send requests to the provided URI using a provided RestTemplate * @param uri The URI. * @param restTemplate The rest template. */ public HttpRequestExecutingMessageHandler(String uri, RestTemplate restTemplate) { this(new LiteralExpression(uri), restTemplate); /* * We'd prefer to do this assertion first, but the compiler doesn't allow it. However, * it's safe because the literal expression simply wraps the String variable, even * when null. */ Assert.hasText(uri, "URI is required"); } /** * Create a handler that will send requests to the provided URI using a provided RestTemplate * @param uriExpression A SpEL Expression that can be resolved against the message object and * {@link org.springframework.beans.factory.BeanFactory}. * @param restTemplate The rest template. */ public HttpRequestExecutingMessageHandler(Expression uriExpression, RestTemplate restTemplate) { super(uriExpression); this.restTemplate = (restTemplate == null ? new RestTemplate() : restTemplate); } @Override public String getComponentType() { return (this.isExpectReply() ? "http:outbound-gateway" : "http:outbound-channel-adapter"); } /** * Set the {@link ResponseErrorHandler} for the underlying {@link RestTemplate}. * @param errorHandler The error handler. * @see RestTemplate#setErrorHandler(ResponseErrorHandler) */ public void setErrorHandler(ResponseErrorHandler errorHandler) { this.restTemplate.setErrorHandler(errorHandler); } /** * Set a list of {@link HttpMessageConverter}s to be used by the underlying {@link RestTemplate}. * Converters configured via this method will override the default converters. * @param messageConverters The message converters. * @see RestTemplate#setMessageConverters(java.util.List) */ public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) { this.restTemplate.setMessageConverters(messageConverters); } /** * Set the {@link ClientHttpRequestFactory} for the underlying {@link RestTemplate}. * @param requestFactory The request factory. * @see RestTemplate#setRequestFactory(ClientHttpRequestFactory) */ public void setRequestFactory(ClientHttpRequestFactory requestFactory) { this.restTemplate.setRequestFactory(requestFactory); } @Override protected Object exchange(Supplier<URI> uriSupplier, HttpMethod httpMethod, HttpEntity<?> httpRequest, Object expectedResponseType, Message<?> requestMessage) { URI uri = uriSupplier.get(); ResponseEntity<?> httpResponse; try { if (expectedResponseType instanceof ParameterizedTypeReference<?>) { httpResponse = this.restTemplate.exchange(uri, httpMethod, httpRequest, (ParameterizedTypeReference<?>) expectedResponseType); } else { httpResponse = this.restTemplate.exchange(uri, httpMethod, httpRequest, (Class<?>) expectedResponseType); } return getReply(httpResponse); } catch (RestClientException e) { throw new MessageHandlingException(requestMessage, "HTTP request execution failed for URI [" + uri + "] in the [" + this + ']', e); } } }