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。