1 场景
java开发中，使用http连接，访问第三方网络接口，通常使用的连接工具为HttpClient和OKHttp。
这两种连接工具，使用起来比较复杂，新手容易出问题。如果使用spring框架，可以使用restTemplate来进行http连接请求。
restTemplate默认的连接方式是java中的HttpConnection，可以使用ClientHttpRequestFactory指定不同的HTTP连接方式。
2 依赖
maven依赖如下：
<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>
3 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连接管理器
* @return
*/
@Bean
public HttpClientConnectionManager poolingHttpClientConnectionManager() {
/*// 注册http和https请求
Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
.register("http", PlainConnectionSocketFactory.getSocketFactory())
.register("https", SSLConnectionSocketFactory.getSocketFactory())
.build();
PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(registry);*/
PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager();
// 最大连接数
poolingHttpClientConnectionManager.setMaxTotal(500);
// 同路由并发数（每个主机的并发）
poolingHttpClientConnectionManager.setDefaultMaxPerRoute(100);
return poolingHttpClientConnectionManager;
}
/**
* HttpClient
* @param poolingHttpClientConnectionManager
* @return
*/
@Bean
public HttpClient httpClient(HttpClientConnectionManager poolingHttpClientConnectionManager) {
HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
// 设置http连接管理器
httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager);
/*// 设置重试次数
httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(3, true));*/
// 设置默认请求头
/*List<Header> headers = new ArrayList<>();
headers.add(new BasicHeader("Connection", "Keep-Alive"));
httpClientBuilder.setDefaultHeaders(headers);*/
return httpClientBuilder.build();
}
/**
* 请求连接池配置
* @param httpClient
* @return
*/
@Bean
public ClientHttpRequestFactory clientHttpRequestFactory(HttpClient httpClient) {
HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
// httpClient创建器
clientHttpRequestFactory.setHttpClient(httpClient);
// 连接超时时间/毫秒（连接上服务器(握手成功)的时间，超出抛出connect timeout）
clientHttpRequestFactory.setConnectTimeout(5 * 1000);
// 数据读取超时时间(socketTimeout)/毫秒（务器返回数据(response)的时间，超过抛出read timeout）
clientHttpRequestFactory.setReadTimeout(10 * 1000);
// 连接池获取请求连接的超时时间，不宜过长，必须设置/毫秒（超时间未拿到可用连接，会抛出org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool）
clientHttpRequestFactory.setConnectionRequestTimeout(10 * 1000);
return clientHttpRequestFactory;
}
/**
* rest模板
* @return
*/
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory clientHttpRequestFactory) {
// boot中可使用RestTemplateBuilder.build创建
RestTemplate restTemplate = new RestTemplate();
// 配置请求工厂
restTemplate.setRequestFactory(clientHttpRequestFactory);
return restTemplate;
}
}
4 使用
使用到的实体类如下：
@Data
@ToString
public class TempUser implements Serializable {
private String userName;
private Integer age;
}
4.1 GET请求
后台接口代码：
@RequestMapping("getUser")
public TempUser getUser(TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
4.1.1 普通访问
TempUser result = restTemplate.getForObject("http://localhost:8080/cs-admin/rest/getUser?userName=张三&age=18", TempUser.class);
4.1.2 返回HTTP状态
ResponseEntity<TempUser> responseEntity = restTemplate.getForEntity("http://localhost:8080/cs-admin/rest/getUser?userName=张三&age=18", TempUser.class);
// 获取状态对象
HttpStatus httpStatus = responseEntity.getStatusCode();
// 获取状态码
int statusCodeValue = responseEntity.getStatusCodeValue();
// 获取headers
HttpHeaders httpHeaders = responseEntity.getHeaders();
// 获取body
TempUser result = responseEntity.getBody();
4.1.3 映射请求参数
Map<String, Object> paramMap = new HashMap<>();
paramMap.put("userName", "张三");
paramMap.put("age", 18);
TempUser result = restTemplate.getForObject("http://localhost:8080/cs-admin/rest/getUser?userName={userName}&age={age}", TempUser.class, paramMap);
4.2 POST请求
4.2.1 普通访问
后台接口代码：
RequestMapping("getPostUser")
public TempUser getPostUser(@RequestBody TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
（1）普通访问接口
TempUser param = new TempUser();
param.setUserName("张三");
param.setAge(18);
TempUser result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/getPostUser", param, TempUser.class);
（2）带HEAD访问接口
// 请求头信息
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.valueOf("application/json;charset=UTF-8"));
//headers.add("headParam1", "headParamValue");
// 请求体内容
TempUser param = new TempUser();
param.setUserName("张三");
param.setAge(18);
// 组装请求信息
HttpEntity<TempUser> httpEntity=new HttpEntity<>(param,headers);
TempUser result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/getPostUser", httpEntity, TempUser.class);
4.2.2 无请求体的访问
仅method为post，传参方式仍然为get的param方式
后台接口代码：
@RequestMapping("getPostUserNoBody")
public TempUser getPostUserNoBody(TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
访问方式：
Map<String, Object> paramMap = new HashMap<>();
paramMap.put("userName", "张三");
paramMap.put("age", 18);
TempUser result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/getPostUserNoBody?userName={userName}&age={age}", null, TempUser.class, paramMap);
System.out.println(result);
4.3 上传文件
后台接口代码：
@RequestMapping("uploadFile")
public TempUser uploadFile(HttpServletRequest request, TempUser form) {
MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
//获取文件信息
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;
}
访问方式：
// 文件
FileSystemResource file=new FileSystemResource("D:\\Elasticsearch权威指南（中文版）.pdf");
// 设置请求内容
MultiValueMap<String, Object> param=new LinkedMultiValueMap<>();
param.add("file", file);
// 其他参数
param.add("userName", "张三");
param.add("age", 18);
// 组装请求信息
HttpEntity<MultiValueMap<String, Object>> httpEntity=new HttpEntity<>(param);
// 发送请求
TempUser result = restTemplate.postForObject("http://localhost:8080/cs-admin/rest/uploadFile", httpEntity, TempUser.class);
