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常見的遠程調用方式有以下2種：
RPC： Remote Produce Call遠程過程調用，類似的還有RMI（remote method invoke）。自定義數據格式，基于原生TCP通信，速度快，效率高。早期的webservice，現在熱門的dubbo，都是RPC的典型代表。
Http： http其實是一種網絡傳輸協議，基于TCP，規定了數據傳輸的格式。 現在客戶端瀏覽器與服務端通信基本都是采用Http協議，也可以用來進行遠程服務調用。缺點是消息封裝臃腫，優勢是對服務的提供和調用方沒有任何技術限定，自由靈活，更符合微服務理念?，F在熱門的Rest風格，就可以通過http協議來實現。
如果項目全部采用 Java技術棧，那么使用Dubbo作為微服務架構是一個不錯的選擇。
如果項目的技術棧多樣化，主要采用了Spring和SpringBoot框架，那么SpringCloud搭建微服務是不二之選，使用Http方式來實現服務間調用。
java開發中，使用http連接，訪問第三方網絡接口，通常使用的連接工具為RestTemplate、HttpClient和OKHttp。
HttpClient和OKHttp兩種連接工具，使用起來比較復雜，如果使用spring框架，可以使用restTemplate來進行http連接請求。
restTemplate默認的連接方式是java中的HttpConnection，可以使用ClientHttpRequestFactory指定不同的HTTP連接方式。
依賴
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>5.2.2.RELEASE</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.7</version> </dependency>
基礎配置
@Configuration
public class RestTemplateConfig {
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
return new RestTemplate(factory);
}
@Bean
public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
factory.setReadTimeout(150 * 1000); // ms
factory.setConnectTimeout(150 * 1000); // ms
return factory;
}
}進階配置
import org.apache.http.client.HttpClient;
import org.apache.http.conn.HttpClientConnectionManager;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;
@Configuration
public class RestTemplateConfig {
/**
* http連接管理器
*/
@Bean
public HttpClientConnectionManager poolingHttpClientConnectionManager() {
/*// 注冊http和https請求
Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
.register("http", PlainConnectionSocketFactory.getSocketFactory())
.register("https", SSLConnectionSocketFactory.getSocketFactory())
.build();
PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(registry);*/
PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager();
// 最大連接數
poolingHttpClientConnectionManager.setMaxTotal(500);
// 同路由并發數（每個主機的并發）
poolingHttpClientConnectionManager.setDefaultMaxPerRoute(100);
return poolingHttpClientConnectionManager;
}
/**
* HttpClient
* @param poolingHttpClientConnectionManager
*/
@Bean
public HttpClient httpClient(HttpClientConnectionManager poolingHttpClientConnectionManager) {
HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
// 設置http連接管理器
httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager);
/*// 設置重試次數，默認是3次，沒有開啟
httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(3, true));*/
// 設置默認請求頭
/*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"));
headers.add(new BasicHeader("Content-type", "application/json;charset=UTF-8"));
httpClientBuilder.setDefaultHeaders(headers);*/
return httpClientBuilder.build();
}
/**
* 請求連接池配置
* @param httpClient
*/
@Bean
public ClientHttpRequestFactory clientHttpRequestFactory(HttpClient httpClient) {
HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
// httpClient創建器
clientHttpRequestFactory.setHttpClient(httpClient);
// 連接超時時間/毫秒（連接上服務器(握手成功)的時間，超出拋出connect timeout）
clientHttpRequestFactory.setConnectTimeout(5 * 1000);
// 數據讀取超時時間(socketTimeout)/毫秒（服務器返回數據(response)的時間，超過拋出read timeout）
clientHttpRequestFactory.setReadTimeout(10 * 1000);
// 從連接池獲取請求連接的超時時間，不宜過長，必須設置/毫秒（超時間未拿到可用連接，會拋出org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool）
clientHttpRequestFactory.setConnectionRequestTimeout(10 * 1000);
return clientHttpRequestFactory;
}
/**
* rest模板
*/
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory clientHttpRequestFactory) {
// 配置請求工廠
return new RestTemplate(clientHttpRequestFactory);
}
}實體類
@Data
@Builder
@NoArgsConstrutor
@AllArgsConstrutor
public class BaseResponse<TempUser> implements Serializable {
private static final long serialVersionUID = 1L;
private String responseCode;
private String responseMessage;
private List<TempUser> responseData;
}@Data
@Builder
@NoArgsConstrutor
@AllArgsConstrutor
public class TempUser implements Serializable {
private static final long serialVersionUID = 1L;
private String userName;
private Integer age;
}普通訪問
BaseResponse result = restTemplate.getForObject( "http://localhost:8080/cs-admin/rest/getUser?userName=張三&age=18", BaseResponse.class);
返回HTTP狀態
ResponseEntity<BaseResponse> responseEntity = restTemplate.getForEntity( "http://localhost:8080/cs-admin/rest/getUser?userName=張三&age=18", TempUser.class); // 獲取狀態對象 HttpStatus httpStatus = responseEntity.getStatusCode(); // 獲取狀態碼 int statusCodeValue = responseEntity.getStatusCodeValue(); // 獲取headers HttpHeaders httpHeaders = responseEntity.getHeaders(); // 獲取body BaseResponse result = responseEntity.getBody();
映射請求參數
Map<String, Object> paramMap = new HashMap<>();
paramMap.put("userName", "張三");
paramMap.put("age", 18);
BaseResponse result = restTemplate.getForObject(
"http://localhost:8080/cs-admin/rest/getUser?userName={userName}&age={age}",
BaseResponse.class, paramMap);普通訪問接口
TempUser param = new TempUser();
param.setUserName("張三");
param.setAge(18);
BaseResponse result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/getPostUser",
param, BaseResponse.class);帶HEAD訪問接口
// 請求頭信息
HttpHeaders headers = new HttpHeaders();
//headers.setContentType(MediaType.valueOf("application/json;charset=UTF-8"));
headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
//headers.add("headParam1", "headParamValue");
// 請求體內容
TempUser param = new TempUser();
param.setUserName("張三");
param.setAge(18);
// 組裝請求信息
HttpEntity<TempUser> httpEntity=new HttpEntity<>(param, headers);
BaseResponse result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/getPostUser",
httpEntity, BaseResponse.class);無請求體的訪問：僅method為post，傳參方式仍然為get的param方式
Map<String, Object> paramMap = new HashMap<>();
paramMap.put("userName", "張三");
paramMap.put("age", 18);
BaseResponse result = restTemplate.postForObject(
"http://localhost:8080/cs-admin/rest/getPostUserNoBody?userName={userName}&age={age}",
null, BaseResponse.class, paramMap);
System.out.println(result);后臺接口代碼：
@RequestMapping("uploadFile")
public TempUser uploadFile(HttpServletRequest request, TempUser form) {
MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
//獲取文件信息
MultipartFile multipartFile = multipartHttpServletRequest.getFile("file");
TempUser tempUser = new TempUser();
if (multipartFile != null) {
tempUser.setUserName(form.getUserName() + " " + multipartFile.getOriginalFilename());
}
if(form!=null){
tempUser.setAge(form.getAge());
}
return tempUser;
}訪問方式：
// 文件
FileSystemResource file=new FileSystemResource("D:\\Elasticsearch權威指南（中文版）.pdf");
// 設置請求內容
MultiValueMap<String, Object> param=new LinkedMultiValueMap<>();
param.add("file", file);
// 其他參數
param.add("userName", "張三");
param.add("age", 18);
// 組裝請求信息
HttpEntity<MultiValueMap<String, Object>> httpEntity=new HttpEntity<>(param);
// 發送請求
TempUser result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/uploadFile",
httpEntity, TempUser.class);HttpClient 通過連接池創建連接：
管理連接的基本單位是Route（路由），每個路由上都會維護一定數量的HTTP連接
每次調用后必須執行 releaseConnection
路由可以理解為客戶端機器到目標機器的一條線路
如果不給 httpclient配置指定的連接管理器，httpclient會自動使用PoolingHttpClientConnectionManager作為連接管理器。
PoolingHttpClientConnectionManager默認的maxConnPerRoute和maxConnTotal分別是是2和20。也就是對于每個服務器最多只會維護2個連接，看起來有點少。所以，在日常使用時我們盡量使用自己配置的連接管理器比較好。
連接池：
連接池技術作為創建和管理連接的緩沖池技術。
連接池管理的對象是長連接
有長連接的優勢
**長連接：**是指客戶端與服務器端一旦建立連接以后，可以進行多次數據傳輸而不需重新建立連接，
優勢：
省去了每次數據傳輸連接建立的時間開銷
資源的訪問控制
**短連接：**每次數據傳輸都需要客戶端和服務器端建立一次連接
使用HttpClient發送請求、接收響應很簡單，一般需要如下幾步即可:
創建HttpClient對象
創建請求方法的實例，并指定請求URL。如果需要發送GET請求，創建HttpGet對象；如果需要發送POST請求，創建HttpPost對象。
如果需要發送請求參數，可調用HttpGet、HttpPost共同的setParams(HetpParams params)方法來添加請求參數；對于HttpPost對象而言，也可調用setEntity(HttpEntity entity)方法來設置請求參數，參數則必須用NameValuePair[]數組存儲
調用HttpClient對象的execute(HttpUriRequest request)發送請求，該方法返回一個HttpResponse
調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭；調用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內容。程序可通過該對象獲取服務器的響應內容
釋放連接。無論執行方法是否成功，都必須釋放連接
依賴：
<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.2</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient-cache</artifactId> <version>4.5.2</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpmime</artifactId> <version>4.5.2</version> </dependency>
java工具類
import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.http.Consts;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* HttpClient 工具類
*/
@Slf4j
public class HttpClientUtil {
public static final String APPLICATION_JSON_VALUE = "application/json";
private static final Logger logger = log;
private static final Integer CONN_TIME_OUT = 3000;// 超時時間豪秒
private static final Integer SOCKET_TIME_OUT = 10000;
/** 每個路由的最大請求數，默認2 */
private static final Integer DEFAULT_MAX_PER_ROUTE = 40;
/** 最大連接數，默認20 */
private static final Integer MAX_TOTAL = 400;
private static HttpClient httpClient;
static {
// 請求配置
RequestConfig requestConfig = RequestConfig.custom()
.setConnectTimeout(CONN_TIME_OUT)
.setConnectionRequestTimeout(CONN_TIME_OUT)
.setSocketTimeout(SOCKET_TIME_OUT)
.build();
// 管理 http連接池
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setDefaultMaxPerRoute(DEFAULT_MAX_PER_ROUTE);
cm.setMaxTotal(MAX_TOTAL);
httpClient = HttpClients.custom()
.setConnectionManager(cm)
.setDefaultRequestConfig(requestConfig)
.build();
}
/**
* Get請求
*/
public static String requestGet(String url, Map<String, String> paramsMap) throws Exception {
logger.info("GET request url:{} params:{}", url, paramsMap);
Long start = System.currentTimeMillis();
List<NameValuePair> params = initParams(paramsMap);
// Get請求
HttpGet httpGet = new HttpGet(url);
try {
// 設置參數
String str = EntityUtils.toString(new UrlEncodedFormEntity(params, StandardCharsets.UTF_8));
String uriStr = StringUtils.isEmpty(str) ?
httpGet.getURI().toString() : httpGet.getURI().toString() + "?" + str;
httpGet.setURI(new URI(uriStr));
// 發送請求
HttpResponse response = httpClient.execute(httpGet);
logger.info("GET request url:{} response:{} time:{}",
url, response, System.currentTimeMillis() - start);
// 獲取返回數據
return getSuccessRetFromResp(response, url, JSON.toJSONString(paramsMap));
} finally {
// 必須釋放連接，不然連接用完后會阻塞
httpGet.releaseConnection();
}
}
/**
* Post請求，Map格式數據
*/
public static String requestPost(String url, Map<String, String> paramsMap) throws Exception {
logger.info("POST request url:{} params:{}", url, paramsMap);
Long start = System.currentTimeMillis();
List<NameValuePair> params = initParams(paramsMap);
HttpPost httpPost = new HttpPost(url);
try {
httpPost.setEntity(new UrlEncodedFormEntity(params, Consts.UTF_8));
HttpResponse response = httpClient.execute(httpPost);
logger.info("POST request url:{} response:{} time:{}",
url, response, System.currentTimeMillis() - start);
String retStr = getSuccessRetFromResp(response, url, JSON.toJSONString(paramsMap));
return retStr;
} finally {
httpPost.releaseConnection();
}
}
/**
* Post請求，json格式數據
*
*/
public static String requestPostJsonStr(String url, String json) throws Exception {
logger.info("POST request url:{} params:{}", url, json);
long start = System.currentTimeMillis();
HttpPost httpPost = new HttpPost(url);
try {
StringEntity entity = new StringEntity(json, Consts.UTF_8);
entity.setContentType(APPLICATION_JSON_VALUE);
httpPost.setEntity(entity);
HttpResponse response = httpClient.execute(httpPost);
logger.info("POST request url:{} response:{} time:{}",
url, response, System.currentTimeMillis() - start);
return getSuccessRetFromResp(response, url, json);
} finally {
// 資源釋放
httpPost.releaseConnection();
}
}
/**
* post Object格式數據
*/
public static String requestPostJson(String url, Object obj) throws Exception {
String params = JSON.toJSONString(obj);
return requestPostJsonStr(url, params);
}
private static String getSuccessRetFromResp(HttpResponse response, String url, String params) throws Exception {
String retStr = "";
// 檢驗狀態碼，如果成功接收數據
int code = response.getStatusLine().getStatusCode();
if (code == 200) {
retStr = EntityUtils.toString(response.getEntity(), Consts.UTF_8);
} else {
throw new RuntimeException(String.format("Http request error:%s, url:%s, params:%s", response, url, params));
}
logger.info("Http request retStr:{}. url:{}", retStr, url);
return retStr;
}
private static List<NameValuePair> initParams(Map<String, String> paramsMap) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
if (paramsMap == null)
return params;
for (Map.Entry<String, String> entry : paramsMap.entrySet()) {
params.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
}
return params;
}
}以上就是關于“Java服務RestTemplate與HttpClient如何使用”這篇文章的內容，相信大家都有了一定的了解，希望小編分享的內容對大家有幫助，若想了解更多相關的知識內容，請關注億速云行業資訊頻道。
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