什么是RestTemplate？
RestTemplate是Spring提供的用於訪問Rest服務的客戶端，RestTemplate提供了多種便捷訪問遠程Http服務的方法，能夠大大提高客戶端的編寫效率。
調用RestTemplate的默認構造函數，RestTemplate對象在底層通過使用java.net包下的實現創建HTTP 請求，可以通過使用ClientHttpRequestFactory指定不同的HTTP請求方式。
ClientHttpRequestFactory接口主要提供了兩種實現方式
- 一種是SimpleClientHttpRequestFactory，使用J2SE提供的方式（既java.net包提供的方式）創建底層的Http請求連接。
- 一種方式是使用HttpComponentsClientHttpRequestFactory方式，底層使用HttpClient訪問遠程的Http服務，使用HttpClient可以配置連接池和證書等信息。
xml配置的方式
請查看RestTemplate源碼了解細節，知其然知其所以然！
RestTemplate默認是使用SimpleClientHttpRequestFactory，內部是調用jdk的HttpConnection，默認超時為-1
@Autowired
RestTemplate simpleRestTemplate
@Autowired
RestTemplate restTemplate
基於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的實現-->
<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連接池的方式
<?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的實現，帶連接池-->
<bean id="ky.pollingConnectionManager" class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager">
<!--整個連接池的並發-->
<property name="maxTotal" value="1000" />
<!--每個主機的並發-->
<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" />
<!--開啟重試-->
<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"/>
<!--連接超時時間，毫秒-->
<property name="connectTimeout" value="5000"/>
<!--讀寫超時時間，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+靜態工具
線程安全的單例（懶漢模式）
基於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：基於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);
// 添加轉換器
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連接池的方式
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 {
// 長連接保持30秒
PoolingHttpClientConnectionManager pollingConnectionManager = new PoolingHttpClientConnectionManager(30, TimeUnit.SECONDS);
// 總連接數
pollingConnectionManager.setMaxTotal(1000);
// 同路由的並發數
pollingConnectionManager.setDefaultMaxPerRoute(1000);
HttpClientBuilder httpClientBuilder = HttpClients.custom();
httpClientBuilder.setConnectionManager(pollingConnectionManager);
// 重試次數，默認是3次，沒有開啟
httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(2, true));
// 保持長連接配置，需要在頭添加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連接配置，底層是配置RequestConfig
HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
// 連接超時
clientHttpRequestFactory.setConnectTimeout(5000);
// 數據讀取超時時間，即SocketTimeout
clientHttpRequestFactory.setReadTimeout(5000);
// 連接不夠用的等待時間，不宜過長，必須設置，比如連接不夠用時，時間過長將是災難性的
clientHttpRequestFactory.setConnectionRequestTimeout(200);
// 緩沖請求數據，默認值是true。通過POST或者PUT大量發送數據時，建議將此屬性更改為false，以免耗盡內存。
// clientHttpRequestFactory.setBufferRequestBody(false);
// 添加內容轉換器
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;
/**
*
* 類功能說明：httpclient工具類,基於httpclient 4.x
* Title: HttpClientUtils.java
* @author 劉興
* @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請求
* @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請求出錯：{}", url, e);
}
return Strings.EMPTY;
}
/**
* post請求
* @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請求出錯：{}", url, e);
}
return Strings.EMPTY;
}
/**
* get請求
* @param url
* @return
*/
public static String doGet(String url) {
try {
return RestClient.getClient().getForObject(url, String.class);
} catch (Exception e) {
LOGGER.error("GET請求出錯：{}", url, e);
}
return Strings.EMPTY;
}
}
ErrorHolder
自定義的一個異常結果包裝類
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());
}
}
使用樣例
api里面可以做自動的參數匹配：
如：http://you domainn name/test?empNo={empNo}，則下面方法的最后一個參數為數據匹配參數，會自動根據key進行查找，然后替換
API沒有聲明異常，注意進行異常處理
更多使用語法請查看API文檔
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說明和使用參考
http://docs.spring.io/spring/docs/4.1.x/javadoc-api/org/springframework/web/client/RestTemplate.html
HttpClient官方示例和參數配置說明
http://hc.apache.org/httpcomponents-client-4.4.x/examples.html
http://hc.apache.org/httpcomponents-client-4.4.x/tutorial/html/index.html
依賴
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>
注意點
1.關於httpclient配置的defaultMaxPerRoute和maxTotal
defaultMaxPerRoute：最大路由並發數，以主機為單位
maxTotal：整個連接池的並發數
例如：
defaultMaxPerRoute為10，maxTotal為100
假設只會訪問http://www.baidu.com和http://www.google.com
那么能同時並發到客源的只能是10，房源也是10，整個連接永遠不會到100
2.部分方法注意查看源碼，默認構造里面會新增常用的數據轉換器，spring對jackson比較情有獨鍾，在解析xml和json時，優先使用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);
}
再看添加轉換器的方法外部添加轉換器時，this.messageConverters.clear();會先清除已有的，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);
}
}
來自：http://liuxing.info/2015/05/21/RestTemplate%E5%AE%9E%E8%B7%B5/
http://www.open-open.com/lib/view/open1436018677419.html