记录：287

场景：基于Spring Boot使用Java调用http请求的6种方式。服务端发布一个POST请求和2个GET请求。使用6种方式实现的客户端都调用服务端发布的这3个方法。可以直观感受和比对6种http请求的客户端。

版本：

Spring Boot 2.6.3
Spring Framework 5.3.15
Spring Cloud 2021.0.1

一、案例场景

本例实现6种方式客户端调用同一个服务端的3种方法。

1.服务端

在服务端发布一个POST请求，2个GET请求。

1.1 接口信息

(1)POST请求

[访问URL]: http://127.0.0.1:19091/server/comm/f1
[请求方式]: POST
[请求参数]: JSON
{"userName":"HangZhou20220719","tradeName":"Vue进阶教程"}
[返回值]: JSON
{code=200, message=成功}

(2)GET请求(一)

[访问URL]: http://127.0.0.1:19091/server/comm/f2
[请求方式]: GET
[请求参数]: String
obj=HangZhou20220719
[返回值]: JSON
{code=200, message=成功}

(3)GET请求(二)

[访问URL]: http://127.0.0.1:19091/server/comm/f3/{obj}
[请求方式]: GET
[请求参数]: String
obj=HangZhou20220719
[返回值]: JSON
{code=200, message=成功}

1.2 服务端代码

服务端3个接口代码。

@Slf4j
@RestController
@RequestMapping("/comm")
public class CommonController {
  /**
   *  1.发布POST请求
   *    入参注解: @RequestBody
   *    返回注解: @ResponseBody(@RestController包含此注解)
   * */
  @PostMapping("/f1")
  public Object f1(@RequestBody  Object obj) {
    log.info("CommonController->f1,接收参数,obj = " + obj.toString());
    log.info("CommonController->f1,处理业务.");
    log.info("CommonController->f1,返回.");
    return ResultObj.builder().code("200").message("成功").build();
  }
  /**
   *  2.发布GET请求
   *    入参注解: @RequestParam
   *    返回注解: @ResponseBody(@RestController包含此注解)
   * */
  @GetMapping ("/f2")
  public Object f2(@RequestParam("obj") String obj) {
    log.info("CommonController->f2,接收参数,obj = " + obj.toString());
    log.info("CommonController->f2,处理业务.");
    log.info("CommonController->f2,返回.");
    return ResultObj.builder().code("200").message("成功").build();
  }
  /**
   *  3.发布GET请求
   *    入参注解: @PathVariable
   *    返回注解: @ResponseBody(@RestController包含此注解)
   * */
  @GetMapping ("/f3/{obj}")
  public Object f3(@PathVariable("obj") String obj) {
    log.info("CommonController->f3,接收参数,obj = " + obj.toString());
    log.info("CommonController->f3,处理业务.");
    log.info("CommonController->f3,返回.");
    return ResultObj.builder().code("200").message("成功").build();
  }
}

1.3 服务端辅助对象

服务端辅助对象。

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class ResultObj {
  private String code;
  private String message;
}

二、Java调用http请求的6种方式

1.使用HttpURLConnection调用http请求

(1)Jar包位置

HttpURLConnection，全称：java.net.HttpURLConnection。

JDK 1.8中自带的rt.jar包中的java.net包内的类。

(2)客户端代码

public class Utils01JdkClient {
 public static void main(String[] args) throws Exception {
   f1();
   f2();
   f3();
 }
 /**
  * 1.使用HttpURLConnection调用服务端的POST请求
  * 服务端入参注解: @RequestBody
  */
 public static void f1() throws Exception {
   // 1.请求URL
   String postUrl = "http://127.0.0.1:19091/server/comm/f1";
   // 2.请求参数JSON格式
   Map<String, String> map = new HashMap<>();
   map.put("userName", "HangZhou20220718");
   map.put("tradeName", "Vue进阶教程");
   String json = JSON.toJSONString(map);
   // 3.创建连接与设置连接参数
   URL urlObj = new URL(postUrl);
   HttpURLConnection httpConn = (HttpURLConnection) urlObj.openConnection();
   httpConn.setRequestMethod("POST");
   httpConn.setRequestProperty("Charset", "UTF-8");
   // POST请求且JSON数据,必须设置
   httpConn.setRequestProperty("Content-Type", "application/json");
   // 打开输出流,默认是false
   httpConn.setDoOutput(true);
   // 打开输入流,默认是true,可省略
   httpConn.setDoInput(true);
   // 4.从HttpURLConnection获取输出流和写数据
   OutputStream oStream = httpConn.getOutputStream();
   oStream.write(json.getBytes());
   oStream.flush();
   // 5.发起http调用(getInputStream触发http请求)
   if (httpConn.getResponseCode() != 200) {
       throw new Exception("调用服务端异常.");
   }
   // 6.从HttpURLConnection获取输入流和读数据
   BufferedReader br = new BufferedReader(
           new InputStreamReader(httpConn.getInputStream()));
   String resultData = br.readLine();
   System.out.println("从服务端返回结果: " + resultData);
   // 7.关闭HttpURLConnection连接
   httpConn.disconnect();
 }
 /**
  * 2.使用HttpURLConnection调用服务端的GET请求
  * 服务端入参注解: @RequestParam
  */
 public static void f2() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f2";
  String obj = "Vue进阶教程";
  String para = "?obj=" + URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + para;
  // 2.创建连接与设置连接参数
  URL urlObj = new URL(getUrl);
  HttpURLConnection httpConn = (HttpURLConnection) urlObj.openConnection();
  httpConn.setRequestMethod("GET");
  httpConn.setRequestProperty("Charset", "UTF-8");
  // 3.发起http调用(getInputStream触发http请求)
  if (httpConn.getResponseCode() != 200) {
      throw new Exception("调用服务端异常.");
  }
  // 4.从HttpURLConnection获取输入流和读数据
  BufferedReader br = new BufferedReader(
          new InputStreamReader(httpConn.getInputStream()));
  String resultData = br.readLine();
  System.out.println("从服务端返回结果: " + resultData);
  // 5.关闭HttpURLConnection连接
  httpConn.disconnect();
 }
 /**
  * 3.使用HttpURLConnection调用服务端的GET请求
  * 服务端入参注解: @PathVariable
  */
 public static void f3() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f3/";
  String obj = "Vue进阶教程";
  obj = URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + obj;
  URL urlObj = new URL(getUrl);
  // 2.创建连接与设置连接参数
  HttpURLConnection httpConn = (HttpURLConnection) urlObj.openConnection();
   httpConn.setRequestMethod("GET");
   httpConn.setRequestProperty("charset", "UTF-8");
   // 3.发起http调用(getInputStream触发http请求)
   if (httpConn.getResponseCode() != 200) {
       throw new Exception("调用服务端异常.");
   }
   // 4.从HttpURLConnection获取输入流和读数据
   BufferedReader br = new BufferedReader(
           new InputStreamReader(httpConn.getInputStream()));
   String resultData = br.readLine();
   System.out.println("从服务端返回结果: " + resultData);
   // 5.关闭HttpURLConnection连接
   httpConn.disconnect();
 }
}

2.使用commons-httpclient调用http请求

(1)Jar包位置

commons-httpclient，比较早的Jar包，在MVNRepository仓库中，查看的最新维护时间是：2007年8月。

<dependency>
  <groupId>commons-httpclient</groupId>
  <artifactId>commons-httpclient</artifactId>
  <version>3.1</version>
</dependency>

(2)客户端代码

public class Utils02CommonsHttpClient {

 public static void main(String[] args) throws Exception {
  f1();
  f2();
  f3();
 }
 /**
  * 1.使用commons-httpclient调用服务端的POST请求
  * 服务端入参注解: @RequestBody
  */
 public static void f1() throws Exception {
  // 1.请求URL
  String postUrl = "http://127.0.0.1:19091/server/comm/f1";
  // 2.请求参数
  Map<String, String> map = new HashMap<>();
  map.put("userName", "HangZhou20220718");
  map.put("tradeName", "Vue进阶教程");
  String json = JSON.toJSONString(map);
  // 3.创建连接与设置连接参数
  HttpClient httpClient = new HttpClient();
  PostMethod postMethod = new PostMethod(postUrl);
  postMethod.addRequestHeader("Content-Type", "application/json");
  RequestEntity entity = new StringRequestEntity(json, "application/json", "UTF-8");
  postMethod.setRequestEntity(entity);
  //解决返回值中文乱码
  postMethod.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");
  String resultData = "";
  // 4.发起请求
  int code = httpClient.executeMethod(postMethod);
  if (code != 200) {
      throw new Exception("调用服务端异常.");
  }
  // 5.接收返回值
  resultData = postMethod.getResponseBodyAsString();
  System.out.println("从服务端返回结果: " + resultData);
  // 6.关闭连接
  postMethod.releaseConnection();
 }
 /**
  * 2.使用commons-httpclient调用服务端的GET请求
  * 服务端入参注解: @RequestParam
  */
 public static void f2() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f2";
  String obj = "Vue进阶教程";
  //入参有中文需要编码
  String para = "?obj=" + URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + para;
  // 2.创建连接与设置连接参数
  HttpClient httpClient = new HttpClient();
  GetMethod getMethod = new GetMethod(getUrl);
  //解决返回值中文乱码
  getMethod.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");
  // 3.发起请求
  int code = httpClient.executeMethod(getMethod);
  String resultData = "";
  if (code != 200) {
      throw new Exception("调用服务端异常.");
  }
  // 4.接收返回值
  resultData = getMethod.getResponseBodyAsString();
  System.out.println("从服务端返回结果: " + resultData);
  // 5.关闭连接
  getMethod.releaseConnection();
 }
 /**
  * 3.使用commons-httpclient调用服务端的GET请求
  * 服务端入参注解: @PathVariable
  */
 public static void f3() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f3/";
  String obj = "Vue进阶教程";
  //入参有中文需要编码
  obj = URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + obj;
  // 2.创建连接与设置连接参数
  HttpClient httpClient = new HttpClient();
  GetMethod getMethod = new GetMethod(getUrl);
  //解决返回值中文乱码
  getMethod.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");
  // 3.发起请求
  int code = httpClient.executeMethod(getMethod);
  String resultData = "";
  if (code != 200) {
      throw new Exception("调用服务端异常.");
  }
  // 4.接收返回值
  resultData = getMethod.getResponseBodyAsString();
  System.out.println("从服务端返回结果: " + resultData);
  // 5.关闭连接
  getMethod.releaseConnection();
 }
}

3.使用org.apache.httpcomponents调用http请求

(1)Jar包位置

httpcomponents，在MVNRepository仓库中，查看的最新维护时间是：2020年10月。

<dependency>
  <groupId>org.apache.httpcomponents</groupId>
  <artifactId>httpclient</artifactId>
  <version>4.5.13</version>
</dependency>

(2)客户端代码

public class Utils03HttpComponentsClient {
 public static void main(String[] args) throws Exception {
    f1();
    f2();
    f3();
 }
 /**
  * 1.使用org.apache.httpcomponents调用服务端的POST请求
  * 服务端入参注解: @RequestBody
  */
 public static void f1() throws Exception {
   // 1.请求URL
   String postUrl = "http://127.0.0.1:19091/server/comm/f1";
   // 2.请求参数
   Map<String, String> map = new HashMap<>();
   map.put("userName", "HangZhou20220718");
   map.put("tradeName", "Vue进阶教程");
   String json = JSON.toJSONString(map);
   // 3.创建连接与设置连接参数
   CloseableHttpClient httpClient = HttpClientBuilder.create().build();
   HttpPost httpPost = new HttpPost(postUrl);
   StringEntity entity = new StringEntity(json);
   entity.setContentEncoding("UTF-8");
   entity.setContentType("application/json");
   httpPost.setEntity(entity);
   // 4.发起请求与接收返回值
   HttpResponse response = httpClient.execute(httpPost);
   if (response.getStatusLine().getStatusCode() != 200) {
       throw new Exception("调用服务端异常.");
   }
   HttpEntity res = response.getEntity();
   String resultData = EntityUtils.toString(res);
   System.out.println("从服务端返回结果: " + resultData);
   // 5.关闭连接
   httpClient.close();
 }
 /**
  * 2.使用org.apache.httpcomponents调用服务端的GET请求
  * 服务端入参注解: @RequestParam
  */
 public static void f2() throws Exception {
   // 1.请求URL与组装请求参数
   String getUrl = "http://127.0.0.1:19091/server/comm/f2";
   String obj = "Vue进阶教程";
   String para = "?obj=" + URLEncoder.encode(obj, "UTF-8");
   getUrl = getUrl + para;
   // 2.创建连接与设置连接参数
   CloseableHttpClient httpClient = HttpClientBuilder.create().build();
   HttpGet httpGet = new HttpGet(getUrl);
   // 3.发起请求与接收返回值
   HttpResponse response = httpClient.execute(httpGet);
   if (response.getStatusLine().getStatusCode() != 200) {
       throw new Exception("调用服务端异常.");
   }
   HttpEntity res = response.getEntity();
   String resultData = EntityUtils.toString(res);
   System.out.println("从服务端返回结果: " + resultData);
   // 4.关闭连接
   httpClient.close();
 }
 
 /**
  * 3.使用org.apache.httpcomponents调用服务端的GET请求
  * 服务端入参注解: @PathVariable
  */
 public static void f3() throws Exception {
   // 1.请求URL与组装请求参数
   String getUrl = "http://127.0.0.1:19091/server/comm/f3/";
   String obj = "Vue进阶教程";
   //入参有中文需要编码
   obj = URLEncoder.encode(obj, "UTF-8");
   getUrl = getUrl + obj;
   // 2.创建连接与设置连接参数
   CloseableHttpClient httpClient = HttpClientBuilder.create().build();
   HttpGet httpGet = new HttpGet(getUrl);
   // 3.发起请求与接收返回值
   HttpResponse response = httpClient.execute(httpGet);
   if (response.getStatusLine().getStatusCode() != 200) {
       throw new Exception("调用服务端异常.");
   }
   HttpEntity res = response.getEntity();
   String resultData = EntityUtils.toString(res);
   System.out.println("从服务端返回结果: " + resultData);
   // 4.关闭连接
   httpClient.close();
 }
}

4.使用OkHttp调用http请求

(1)Jar包位置

com.squareup.okhttp3，本例使用版本。

<dependency>
  <groupId>com.squareup.okhttp3</groupId>
  <artifactId>okhttp</artifactId>
  <version>4.10.0</version>
  <exclusions>
    <exclusion>
      <groupId>com.google.android</groupId>
      <artifactId>android</artifactId>
    </exclusion>
  </exclusions>
</dependency>

(2)客户端代码

public class Utils04OkHttpClient {
 public static void main(String[] args) throws Exception {
  f1();
  f2();
  f3();
 }
 /**
  *  1.使用okhttp调用服务端的POST请求
  *    服务端入参注解: @RequestBody
  * */
 public static void f1() throws Exception {
  // 1.请求URL
  String postUrl = "http://127.0.0.1:19091/server/comm/f1";
  // 2.请求参数
  Map<String, String> map = new HashMap<>();
  map.put("userName", "HangZhou20220718");
  map.put("tradeName", "Vue进阶教程");
  String json = JSON.toJSONString(map);
  // 3.创建连接与设置连接参数
  MediaType mediaType = MediaType.parse("application/json; charset=UTF-8");
  RequestBody requestBody = RequestBody.Companion.create(json, mediaType);
  Request request = new Request.Builder().url(postUrl).post(requestBody).build();
  OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
  // 4.发起请求与接收返回值
  Response response = okHttpClient.newCall(request).execute();
  String resultData = response.body().string();
  System.out.println("从服务端返回结果: " + resultData);
 }
 /**
  *  2.使用okhttp调用服务端的GET请求
  *    服务端入参注解: @RequestParam
  * */
 public static void f2() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f2";
  String obj = "Vue进阶教程";
  String para = "?obj=" + URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + para;
  // 2.创建连接与设置连接参数
  Request request = new Request.Builder().url(getUrl).build();
  OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
  // 3.发起请求与接收返回值
  Response response = okHttpClient.newCall(request).execute();
  String resultData = response.body().string();
  System.out.println("从服务端返回结果: " + resultData);
 }
 /**
  *  3.使用okhttp调用服务端的GET请求
  *    服务端入参注解: @PathVariable
  * */
 public static void f3() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f3/";
  String obj = "Vue进阶教程";
  obj = URLEncoder.encode(obj, "UTF-8");
  getUrl = getUrl + obj;
  // 2.创建连接与设置连接参数
  Request request = new Request.Builder().url(getUrl).build();
  OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
  // 3.发起请求与接收返回值
  Response response = okHttpClient.newCall(request).execute();
  String resultData = response.body().string();
  System.out.println("从服务端返回结果: " + resultData);
 }
}

5.使用RestTemplate调用http请求

(1)Jar包位置

RestTemplate，全称org.springframework.web.client.RestTemplate。

本例使用版本。

dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-web</artifactId>
  <version>5.3.15</version>
  <scope>compile</scope>
</dependency>

(2)客户端代码

public class Utils05RestTemplateClient {
 public static void main(String[] args) throws Exception {
  f1();
  f2();
  f3();
 }
 /**
  * 1.使用RestTemplate调用服务端的POST请求
  * 服务端入参注解: @RequestBody
  */
 public static void f1() throws Exception {
  // 1.请求URL
  String postUrl = "http://127.0.0.1:19091/server/comm/f1";
  // 2.请求参数JSON格式
  Map<String, String> map = new HashMap<>();
  map.put("userName", "HangZhou20220718");
  map.put("tradeName", "Vue进阶教程");
  String json = JSON.toJSONString(map);
  // 3.创建RestTemplate
  RestTemplate restTemplate = new RestTemplate();
  // 4.设置RestTemplate参数(请求头和body)
  HttpHeaders headers = new HttpHeaders();
  MediaType mediaType = MediaType.parseMediaType("application/json; charset=UTF-8");
  headers.setContentType(mediaType);
  headers.add("Accept", "application/json");
  HttpEntity<String> entity = new HttpEntity<>(json, headers);
  // 5.使用RestTemplate发起请求与接收返回值
  String resultData = restTemplate.postForObject(postUrl, entity, String.class);
  System.out.println("从服务端返回结果: " + resultData);
 }
 /**
  * 2.使用RestTemplate调用服务端的GET请求
  * 服务端入参注解: @RequestParam
  */
 public static void f2() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f2";
  String obj = "Vue进阶教程";
  String para = "?obj=" + obj;
  getUrl = getUrl + para;
  // 2.创建RestTemplate
  RestTemplate restTemplate = new RestTemplate();
  // 3.使用RestTemplate发起请求与接收返回值
  String resultData = restTemplate.getForObject(getUrl, String.class);
  System.out.println("从服务端返回结果: " + resultData);
 }
 /**
  * 3.使用RestTemplate调用服务端的GET请求
  * 服务端入参注解: @PathVariable
  */
 public static void f3() throws Exception {
  // 1.请求URL与组装请求参数
  String getUrl = "http://127.0.0.1:19091/server/comm/f3/";
  String obj = "Vue进阶教程";
  getUrl = getUrl + obj;
  // 2.创建RestTemplate
  RestTemplate restTemplate = new RestTemplate();
  // 3.使用RestTemplate发起请求与接收返回值
  String resultData = restTemplate.getForObject(getUrl, String.class);
  System.out.println("从服务端返回结果: " + resultData);
 }
}

6.使用OpenFeign调用http请求

(1)Jar包位置

Spring Cloud OpenFeign是Spring Cloud全家桶组件成员。

本例版本：Spring Cloud 2021.0.1；spring-cloud-openfeign 3.1.1

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

(2)客户端代码(Feign接口)

@FeignClient(contextId = "utils06OpenFeign",
             value = "example-server")
public interface Utils06OpenFeignClient {
  /**
   *  1.使用openfeign调用服务端的POST请求
   *    服务端入参注解: @RequestBody
   * */
  @ResponseBody
  @PostMapping("/server/comm/f1")
  Object f1(@RequestBody Object obj);
  /**
   *  2.使用openfeign调用服务端的GET请求
   *    服务端入参注解: @RequestParam
   * */
  @ResponseBody
  @GetMapping("/server/comm/f2")
  Object f2(@RequestParam("obj") String obj);
  /**
   *  3.使用openfeign调用服务端的GET请求
   *    服务端入参注解: @PathVariable
   * */
  @ResponseBody
  @GetMapping("/server/comm/f3/{obj}")
  Object f3(@PathVariable("obj") String obj);
}

(3)客户端代码(调用Feign接口)

/**
 *   触发请求: 
 *   http://127.0.0.1:19092/client/exam/f
 * */
@Slf4j
@RestController
@RequestMapping("/exam")
public class ExampleController {
  /**
   *  1.注入Feign接口
   * */
  @Autowired
  private Utils06OpenFeignClient feignClient;
  
  /**
   * 2.调用Feign接口
   * */
  @GetMapping("/f")
  public void f() throws Exception {
 
  log.info("使用Feign调用服务端f1: ");
  Map<String, String> map = new HashMap<>();
  map.put("userName", "HangZhou20220718");
  map.put("tradeName", "Vue进阶教程");
  Object resultDataF1 = feignClient.f1(map);
  log.info("使用Feign调用服务端f1,返回结果: " + resultDataF1);
  
  log.info("使用Feign调用服务端f2: ");
  String obj = "Vue进阶教程";
  Object resultDataF2 = feignClient.f2(obj);
  log.info("使用Feign调用服务端f2,返回结果: " + resultDataF2);
  
  log.info("使用Feign调用服务端f3: ");
  String obj2 = "Vue进阶教程";
  Object resultDataF3 = feignClient.f3(obj2);
  log.info("使用Feign调用服务端f3,返回结果: " + resultDataF3);
 }
}

(4)本例使用基础

Spring Cloud OpenFeign是Spring Cloud 组件，搭建的微服务都是基于Spring Cloud架构。本例两个微服务：

服务端：example-server

客户端：example-feign-client

服务端和客户端都使用Nacos作为服务注册和发现中心，在客户端example-feign-client中整合Spring Cloud OpenFeign，服务端不需要修改。在启动类中加@EnableFeignClients注解，在使用OpenFeign的接口上加@FeignClient注解。

以上，感谢。

2022年7月20日

# spring boot # java
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