Spring提供的用于访问Rest服务的客户端：RestTemplate实践
jopen
9年前
什么是RestTemplate？
RestTemplate是Spring提供的用于访问Rest服务的客户端，RestTemplate提供了多种便捷访问远程Http服务的方法，能够大大提高客户端的编写效率。
调用RestTemplate的默认构造函数，RestTemplate对象在底层通过使用java.net包下的实现创建HTTP 请求，可以通过使用ClientHttpRequestFactory指定不同的HTTP请求方式。
ClientHttpRequestFactory接口主要提供了两种实现方式
- 一种是SimpleClientHttpRequestFactory，使用J2SE提供的方式（既java.net包提供的方式）创建底层的Http请求连接。
- 一种方式是使用HttpComponentsClientHttpRequestFactory方式，底层使用HttpClient访问远程的Http服务，使用HttpClient可以配置连接池和证书等信息。
xml配置的方式
请查看RestTemplate源码了解细节，知其然知其所以然！
RestTemplate默认是使用SimpleClientHttpRequestFactory，内部是调用jdk的HttpConnection，默认超时为-1
<p>@AutowiredRestTemplate simpleRestTemplate
@Autowired
RestTemplate restTemplate </p>
基于jdk的spring的RestTemplate
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd" default-autowire="byName" default-lazy-init="true"> <!--方式一、使用jdk的实现--> <bean id="ky.requestFactory" class="org.springframework.http.client.SimpleClientHttpRequestFactory"> <property name="readTimeout" value="10000"/> <property name="connectTimeout" value="5000"/> </bean> <bean id="simpleRestTemplate" class="org.springframework.web.client.RestTemplate"> <constructor-arg ref="ky.requestFactory"/> <property name="messageConverters"> <list> <bean class="org.springframework.http.converter.FormHttpMessageConverter"/> <bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter"/> <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/> <bean class="org.springframework.http.converter.StringHttpMessageConverter"> <property name="supportedMediaTypes"> <list> <value>text/plain;charset=UTF-8</value> </list> </property> </bean> </list> </property> </bean> </beans>
使用Httpclient连接池的方式
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd" default-autowire="byName" default-lazy-init="true"> <!--方式二、使用httpclient的实现，带连接池--> <bean id="ky.pollingConnectionManager" class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager"> <!--整个连接池的并发--> <property name="maxTotal" value="1000" /> <!--每个主机的并发--> <property name="defaultMaxPerRoute" value="1000" /> </bean> <bean id="ky.httpClientBuilder" class="org.apache.http.impl.client.HttpClientBuilder" factory-method="create"> <property name="connectionManager" ref="ky.pollingConnectionManager" /> <!--开启重试--> <property name="retryHandler"> <bean class="org.apache.http.impl.client.DefaultHttpRequestRetryHandler"> <constructor-arg value="2"/> <constructor-arg value="true"/> </bean> </property> <property name="defaultHeaders"> <list> <bean class="org.apache.http.message.BasicHeader"> <constructor-arg value="User-Agent"/> <constructor-arg value="Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.16 Safari/537.36"/> </bean> <bean class="org.apache.http.message.BasicHeader"> <constructor-arg value="Accept-Encoding"/> <constructor-arg value="gzip,deflate"/> </bean> <bean class="org.apache.http.message.BasicHeader"> <constructor-arg value="Accept-Language"/> <constructor-arg value="zh-CN"/> </bean> </list> </property> </bean> <bean id="ky.httpClient" factory-bean="ky.httpClientBuilder" factory-method="build" /> <bean id="ky.clientHttpRequestFactory" class="org.springframework.http.client.HttpComponentsClientHttpRequestFactory"> <constructor-arg ref="ky.httpClient"/> <!--连接超时时间，毫秒--> <property name="connectTimeout" value="5000"/> <!--读写超时时间，毫秒--> <property name="readTimeout" value="10000"/> </bean> <bean id="restTemplate" class="org.springframework.web.client.RestTemplate"> <constructor-arg ref="ky.clientHttpRequestFactory"/> <property name="errorHandler"> <bean class="org.springframework.web.client.DefaultResponseErrorHandler"/> </property> <property name="messageConverters"> <list> <bean class="org.springframework.http.converter.FormHttpMessageConverter"/> <bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter"/> <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/> <bean class="org.springframework.http.converter.StringHttpMessageConverter"> <property name="supportedMediaTypes"> <list> <value>text/plain;charset=UTF-8</value> </list> </property> </bean> </list> </property> </bean> </beans>
bean初始化+静态工具
线程安全的单例（懒汉模式）
基于jdk的spring的RestTemplate
import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.context.annotation.Lazy; import org.springframework.http.client.SimpleClientHttpRequestFactory; import org.springframework.http.converter.FormHttpMessageConverter; import org.springframework.http.converter.HttpMessageConverter; import org.springframework.http.converter.StringHttpMessageConverter; import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter; import org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter; import org.springframework.stereotype.Component; import org.springframework.web.client.DefaultResponseErrorHandler; import org.springframework.web.client.RestTemplate; import javax.annotation.PostConstruct; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.List; /** * @title：基于jdk的spring的RestTemplate * @author：liuxing * @date：2015-05-18 09:35 */ @Component @Lazy(false) public class SimpleRestClient { private static final Logger LOGGER = LoggerFactory.getLogger(SimpleRestClient.class); private static RestTemplate restTemplate; static { SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory(); requestFactory.setReadTimeout(5000); requestFactory.setConnectTimeout(5000); // 添加转换器 List<HttpMessageConverter<?>> messageConverters = new ArrayList<>(); messageConverters.add(new StringHttpMessageConverter(Charset.forName("UTF-8"))); messageConverters.add(new FormHttpMessageConverter()); messageConverters.add(new MappingJackson2XmlHttpMessageConverter()); messageConverters.add(new MappingJackson2HttpMessageConverter()); restTemplate = new RestTemplate(messageConverters); restTemplate.setRequestFactory(requestFactory); restTemplate.setErrorHandler(new DefaultResponseErrorHandler()); LOGGER.info("SimpleRestClient初始化完成"); } private SimpleRestClient() { } @PostConstruct public static RestTemplate getClient() { return restTemplate; } }使用Httpclient连接池的方式
import org.apache.http.Header; import org.apache.http.client.HttpClient; import org.apache.http.impl.client.DefaultConnectionKeepAliveStrategy; import org.apache.http.impl.client.DefaultHttpRequestRetryHandler; import org.apache.http.impl.client.HttpClientBuilder; import org.apache.http.impl.client.HttpClients; import org.apache.http.impl.conn.PoolingHttpClientConnectionManager; import org.apache.http.message.BasicHeader; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.context.annotation.Lazy; import org.springframework.http.client.HttpComponentsClientHttpRequestFactory; import org.springframework.http.converter.FormHttpMessageConverter; import org.springframework.http.converter.HttpMessageConverter; import org.springframework.http.converter.StringHttpMessageConverter; import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter; import org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter; import org.springframework.stereotype.Component; import org.springframework.web.client.DefaultResponseErrorHandler; import org.springframework.web.client.RestTemplate; import javax.annotation.PostConstruct; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.List; import java.util.concurrent.TimeUnit; /** * @title：使用spring的restTemplate替代httpclient工具 * @author：liuxing * @date：2015-05-18 08:48 */ @Component @Lazy(false) public class RestClient { private static final Logger LOGGER = LoggerFactory.getLogger(SimpleRestClient.class); private static RestTemplate restTemplate; static { // 长连接保持30秒 PoolingHttpClientConnectionManager pollingConnectionManager = new PoolingHttpClientConnectionManager(30, TimeUnit.SECONDS); // 总连接数 pollingConnectionManager.setMaxTotal(1000); // 同路由的并发数 pollingConnectionManager.setDefaultMaxPerRoute(1000); HttpClientBuilder httpClientBuilder = HttpClients.custom(); httpClientBuilder.setConnectionManager(pollingConnectionManager); // 重试次数，默认是3次，没有开启 httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(2, true)); // 保持长连接配置，需要在头添加Keep-Alive httpClientBuilder.setKeepAliveStrategy(new DefaultConnectionKeepAliveStrategy()); // RequestConfig.Builder builder = RequestConfig.custom(); // builder.setConnectionRequestTimeout(200); // builder.setConnectTimeout(5000); // builder.setSocketTimeout(5000); // // RequestConfig requestConfig = builder.build(); // httpClientBuilder.setDefaultRequestConfig(requestConfig); List<Header> headers = new ArrayList<>(); headers.add(new BasicHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.16 Safari/537.36")); headers.add(new BasicHeader("Accept-Encoding", "gzip,deflate")); headers.add(new BasicHeader("Accept-Language", "zh-CN")); headers.add(new BasicHeader("Connection", "Keep-Alive")); httpClientBuilder.setDefaultHeaders(headers); HttpClient httpClient = httpClientBuilder.build(); // httpClient连接配置，底层是配置RequestConfig HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(httpClient); // 连接超时 clientHttpRequestFactory.setConnectTimeout(5000); // 数据读取超时时间，即SocketTimeout clientHttpRequestFactory.setReadTimeout(5000); // 连接不够用的等待时间，不宜过长，必须设置，比如连接不够用时，时间过长将是灾难性的 clientHttpRequestFactory.setConnectionRequestTimeout(200); // 缓冲请求数据，默认值是true。通过POST或者PUT大量发送数据时，建议将此属性更改为false，以免耗尽内存。 // clientHttpRequestFactory.setBufferRequestBody(false); // 添加内容转换器 List<HttpMessageConverter<?>> messageConverters = new ArrayList<>(); messageConverters.add(new StringHttpMessageConverter(Charset.forName("UTF-8"))); messageConverters.add(new FormHttpMessageConverter()); messageConverters.add(new MappingJackson2XmlHttpMessageConverter()); messageConverters.add(new MappingJackson2HttpMessageConverter()); restTemplate = new RestTemplate(messageConverters); restTemplate.setRequestFactory(clientHttpRequestFactory); restTemplate.setErrorHandler(new DefaultResponseErrorHandler()); LOGGER.info("RestClient初始化完成"); } private RestClient() { } @PostConstruct public static RestTemplate getClient() { return restTemplate; } }HttpClientUtils
import com.dooioo.commons.Strings; import com.dooioo.framework.SpringContextHolder; import com.dooioo.ky.cache.HttpClientResultCache; import org.apache.commons.collections.MapUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.http.HttpEntity; import org.springframework.util.LinkedMultiValueMap; import org.springframework.util.MultiValueMap; import java.util.Map; /** * * 类功能说明：httpclient工具类,基于httpclient 4.x * Title: HttpClientUtils.java * @author 刘兴 * @date 2014-3-7 下午7:48:58 * @version V1.0 */ public class HttpClientUtils { private static final Logger LOGGER = LoggerFactory.getLogger(HttpClientUtils.class); /** * post请求 * @param url * @param formParams * @return */ public static String doPost(String url, Map<String, String> formParams) { if (MapUtils.isEmpty(formParams)) { return doPost(url); } try { MultiValueMap<String, String> requestEntity = new LinkedMultiValueMap<>(); formParams.keySet().stream().forEach(key -> requestEntity.add(key, MapUtils.getString(formParams, key, ""))); return RestClient.getClient().postForObject(url, requestEntity, String.class); } catch (Exception e) { LOGGER.error("POST请求出错：{}", url, e); } return Strings.EMPTY; } /** * post请求 * @param url * @return */ public static String doPost(String url) { try { return RestClient.getClient().postForObject(url, HttpEntity.EMPTY, String.class); } catch (Exception e) { LOGGER.error("POST请求出错：{}", url, e); } return Strings.EMPTY; } /** * get请求 * @param url * @return */ public static String doGet(String url) { try { return RestClient.getClient().getForObject(url, String.class); } catch (Exception e) { LOGGER.error("GET请求出错：{}", url, e); } return Strings.EMPTY; } }ErrorHolder
自定义的一个异常结果包装类
import org.springframework.http.HttpHeaders; import org.springframework.http.HttpStatus; import org.springframework.web.client.HttpClientErrorException; import org.springframework.web.client.HttpServerErrorException; /** * @title：ErrorHolder * @author：liuxing * @date：2015-06-16 11:01 */ public class ErrorHolder { private HttpStatus statusCode; private String statusText; private String responseBody; private HttpHeaders responseHeaders; public ErrorHolder(HttpStatus statusCode, String statusText, String responseBody) { this.statusCode = statusCode; this.statusText = statusText; this.responseBody = responseBody; } public ErrorHolder(String statusText) { this.statusText = statusText; } public HttpStatus getStatusCode() { return statusCode; } public void setStatusCode(HttpStatus statusCode) { this.statusCode = statusCode; } public String getStatusText() { return statusText; } public void setStatusText(String statusText) { this.statusText = statusText; } public String getResponseBody() { return responseBody; } public void setResponseBody(String responseBody) { this.responseBody = responseBody; } public HttpHeaders getResponseHeaders() { return responseHeaders; } public void setResponseHeaders(HttpHeaders responseHeaders) { this.responseHeaders = responseHeaders; } public static ErrorHolder build(Exception exception) { if (exception instanceof HttpServerErrorException) { HttpServerErrorException e = (HttpServerErrorException) exception; return new ErrorHolder(e.getStatusCode(), e.getStatusText(), e.getResponseBodyAsString()); } if (exception instanceof HttpClientErrorException) { HttpClientErrorException e = (HttpClientErrorException) exception; return new ErrorHolder(e.getStatusCode(), e.getStatusText(), e.getResponseBodyAsString()); } return new ErrorHolder(exception.getMessage()); } }使用样例
api里面可以做自动的参数匹配：
如：http://you domainn name/test?empNo={empNo}，则下面方法的最后一个参数为数据匹配参数，会自动根据key进行查找，然后替换
API没有声明异常，注意进行异常处理
更多使用语法请查看API文档
ResponseEntity<List<KyArea>> result = RestClient.getClient().exchange(DIVIDE_PLATE_API, HttpMethod.GET, HttpEntity.EMPTY, new ParameterizedTypeReference<List<KyArea>>() {}, map("empNo", empNo)); List<KyArea> list = result.getBody(); ResponseEntity<KyArea> result = RestClient.getClient().exchange(DIVIDE_PLATE_API, HttpMethod.GET, HttpEntity.EMPTY, KyArea.class, map("empNo", empNo)); KyArea kyArea = result.getBody();更多
RestTemplate API说明和使用参考
http://docs.spring.io/spring/docs/4.1.x/javadoc-api/org/springframework/web/client/RestTemplate.html
HttpClient官方示例和参数配置说明
http://hc.apache.org/httpcomponents-client-4.4.x/examples.html
http://hc.apache.org/httpcomponents-client-4.4.x/tutorial/html/index.html
依赖spring 3.x以上
<dependency> <groupId>com.fasterxml.jackson.dataformat</groupId> <artifactId>jackson-dataformat-xml</artifactId> <version>2.5.3</version> </dependency> <dependency> <groupId>org.codehaus.jackson</groupId> <artifactId>jackson-mapper-asl</artifactId> <version>1.9.13</version> </dependency>
注意点
1.关于httpclient配置的defaultMaxPerRoute和maxTotal
defaultMaxPerRoute：最大路由并发数，以主机为单位
maxTotal：整个连接池的并发数
例如：
defaultMaxPerRoute为10，maxTotal为100
假设只会访问http://www.baidu.com和http://www.google.com
那么能同时并发到客源的只能是10，房源也是10，整个连接永远不会到100
2.部分方法注意查看源码，默认构造里面会新增常用的数据转换器，spring对jackson比较情有独钟，在解析xml和json时，优先使用jackson
/** * Create a new instance of the {@link RestTemplate} using default settings. * Default {@link HttpMessageConverter}s are initialized. */ public RestTemplate() { this.messageConverters.add(new ByteArrayHttpMessageConverter()); this.messageConverters.add(new StringHttpMessageConverter()); this.messageConverters.add(new ResourceHttpMessageConverter()); this.messageConverters.add(new SourceHttpMessageConverter<Source>()); this.messageConverters.add(new AllEncompassingFormHttpMessageConverter()); if (romePresent) { this.messageConverters.add(new AtomFeedHttpMessageConverter()); this.messageConverters.add(new RssChannelHttpMessageConverter()); } if (jackson2XmlPresent) { messageConverters.add(new MappingJackson2XmlHttpMessageConverter()); } else if (jaxb2Present) { this.messageConverters.add(new Jaxb2RootElementHttpMessageConverter()); } if (jackson2Present) { this.messageConverters.add(new MappingJackson2HttpMessageConverter()); } else if (gsonPresent) { this.messageConverters.add(new GsonHttpMessageConverter()); } } /** * Create a new instance of the {@link RestTemplate} based on the given {@link ClientHttpRequestFactory}. * @param requestFactory HTTP request factory to use * @see org.springframework.http.client.SimpleClientHttpRequestFactory * @see org.springframework.http.client.HttpComponentsClientHttpRequestFactory */ public RestTemplate(ClientHttpRequestFactory requestFactory) { this(); setRequestFactory(requestFactory); }再看添加转换器的方法外部添加转换器时，this.messageConverters.clear();会先清除已有的，需要注意
/** * Create a new instance of the {@link RestTemplate} using the given list of * {@link HttpMessageConverter} to use * @param messageConverters the list of {@link HttpMessageConverter} to use * @since 3.2.7 */ public RestTemplate(List<HttpMessageConverter<?>> messageConverters) { Assert.notEmpty(messageConverters, "'messageConverters' must not be empty"); this.messageConverters.addAll(messageConverters); } /** * Set the message body converters to use. * <p>These converters are used to convert from and to HTTP requests and responses. */ public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) { Assert.notEmpty(messageConverters, "'messageConverters' must not be empty"); // Take getMessageConverters() List as-is when passed in here if (this.messageConverters != messageConverters) { this.messageConverters.clear(); this.messageConverters.addAll(messageConverters); } }来自：http://liuxing.info/2015/05/21/RestTemplate%E5%AE%9E%E8%B7%B5/