Spring提供的用于訪問Rest服務的客戶端：RestTemplate實踐

jopen 9年前發布 | 686K 次閱讀 WEB服務/RPC/SOA RestTemplate
什么是RestTemplate？
RestTemplate是Spring提供的用于訪問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
基于jdk的spring的RestTemplate

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans 

<!--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></pre>

使用Httpclient連接池的方式 

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans 

<!--方式二、使用httpclient的實現，帶連接池-->
<bean id="ky.pollingConnectionManager" class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager">
    <!--整個連接池的并發-->
    <property name="maxTotal" value="1000" />
    <!--每個主機的并發-->
    <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></pre>

bean初始化+靜態工具 

線程安全的單例（懶漢模式） 

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;

}


}</pre>

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);
 // 同路由的并發數
 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;
}


}</pre>

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,基于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;
}




}</pre>

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());

}
}</pre>

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();</pre>

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 

http://docs.spring.io/spring/docs/4.1.x/javadoc-api/org/springframework/http/client/SimpleClientHttpRequestFactory.html 

http://docs.spring.io/spring/docs/4.1.x/javadoc-api/org/springframework/http/client/HttpComponentsClientHttpRequestFactory.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></pre>

注意點 

1.關于httpclient配置的defaultMaxPerRoute和maxTotal

defaultMaxPerRoute：最大路由并發數，以主機為單位

maxTotal：整個連接池的并發數 

例如：

defaultMaxPerRoute為10，maxTotal為100

假設只會訪問http://www.baidu.com和http://www.google.com

那么能同時并發到客源的只能是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比較情有獨鐘，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);
}</pre>

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);

 }
}</pre>

來自：http://liuxing.info/2015/05/21/RestTemplate%E5%AE%9E%E8%B7%B5/
本文由用戶 jopen 自行上傳分享，僅供網友學習交流。所有權歸原作者，若您的權利被侵害，請聯系管理員。
轉載本站原創文章，請注明出處，并保留原始鏈接、圖片水印。
本站是一個以用戶分享為主的開源技術平臺，歡迎各類分享！
本文地址：http://www.baiduhome.net/lib/view/open1436018677419.html
WEB服務/RPC/SOA RestTemplate
Spring提供的用于訪問Rest服務的客戶端：RestTemplate實踐

xml配置的方式

基于jdk的spring的RestTemplate

相關經驗

相關資訊

相關文檔

目錄
