一、理论基础
RestTemplate是Springboot中内置的Http请求工具，可以直接注入使用。
两个常用的构造方法如下图 (点击进入文档地址)
从上面可以看出，最简单的方式就是使用默认配置，不需要额外的配置，便可以直接使用该工具。对于请求频次比较低的情况下，默认配置完全够用。
如果需要大量的请求，可以自定义配置，使用HttpClient的连接池。
二、实战代码
2.1 依赖引入
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- 将tomcat替换为undertow -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>
<!-- 自定义的元数据依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<!-- httpclient，为了使用其连接池 -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.12</version>
</dependency>
<!-- for fastjson -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.62</version>
</dependency>
<!-- lombok，减少代码量，idea需要安装lombok插件 -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
2.2 配置项
2.2.1 配置
http:
pool:
# 连接超时
connectTimeout: 5000
connectionRequestTimeout: 5000
defaultMaxPerRoute: 20
# 最大连接数
maxTotal: 100
# 服务器返回数据(response)的时间
socketTimeout: 5000
validateAfterInactivity: 30000
2.2.2 读取配置文件
@Component
@ConfigurationProperties(prefix = "http.pool")
@Data
public class HttpClientProperties {
/**
* 最大连接数
*/
private Integer maxTotal;
/**
* 路由是对最大连接数的细分
* 每个路由基础的连接数
*/
private Integer defaultMaxPerRoute;
/**
* 连接超时时间
*/
private Integer connectTimeout;
/**
* 从连接池中获取连接的超时时间
*/
private Integer connectionRequestTimeout;
/**
* 服务器返回数据(response)的时间
*/
private Integer socketTimeout;
/**
* 可用空闲连接过期时间
* 重用空闲连接时会先检查是否空闲时间超过这个时间，如果超过，释放socket重新建立
*/
private Integer validateAfterInactivity;
}
2.3 配置文件
@Configuration
public class RestTemplateConfig {
private final HttpClientProperties httpClientProperties;
public RestTemplateConfig(HttpClientProperties httpClientProperties) {
this.httpClientProperties = httpClientProperties;
}
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory){
return new RestTemplate(factory);
}
@Bean
public ClientHttpRequestFactory clientHttpRequestFactory(){
return new HttpComponentsClientHttpRequestFactory(httpClient());
}
@Bean
public HttpClient httpClient() {
Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
.register("http", PlainConnectionSocketFactory.getSocketFactory())
.register("https", SSLConnectionSocketFactory.getSocketFactory())
.build();
PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);
connectionManager.setMaxTotal(httpClientProperties.getMaxTotal());
connectionManager.setDefaultMaxPerRoute(httpClientProperties.getDefaultMaxPerRoute());
connectionManager.setValidateAfterInactivity(httpClientProperties.getValidateAfterInactivity());
RequestConfig requestConfig = RequestConfig.custom()
.setSocketTimeout(httpClientProperties.getSocketTimeout())
.setConnectTimeout(httpClientProperties.getConnectTimeout())
.setConnectionRequestTimeout(httpClientProperties.getConnectionRequestTimeout())
.build();
return HttpClientBuilder.create()
.setDefaultRequestConfig(requestConfig)
.setConnectionManager(connectionManager)
.build();
}
}
2.4 简单的工具类
@Component
@Slf4j
public class HttpClientUtils {
private final RestTemplate restTemplate;
public HttpClientUtils(RestTemplate restTemplate) {
this.restTemplate = restTemplate;
}
/**
* Get
*/
public String get(String uri, Map<String, String> param, String token) {
HttpHeaders headers = new HttpHeaders();
headers.set("token", token);
HttpEntity<String> requestEntity = new HttpEntity<>(null, headers);
StringBuilder url = new StringBuilder();
url.append(uri).append("?");
param.forEach((k, v) -> url.append(k).append("=").append(v).append("&"));
String getUrl = url.substring(0, url.length() - 1);
ResponseEntity<CodeResult> response = restTemplate.exchange(getUrl, HttpMethod.GET, requestEntity, CodeResult.class);
return parseCodeResult(response);
}
/**
* post方式请求接口
* - 参数形式：form-data
*/
public String postFormData(String url, MultiValueMap<String, Object> paramMap, String token) {
HttpHeaders headers = new HttpHeaders();
headers.set("token", token);
headers.setContentType(MediaType.MULTIPART_FORM_DATA);
//用HttpEntity封装整个请求报文
HttpEntity<MultiValueMap<String, Object>> files = new HttpEntity<>(paramMap, headers);
ResponseEntity<CodeResult> response = restTemplate.postForEntity(url, files, CodeResult.class);
return parseCodeResult(response);
}
/**
* post方式请求接口
* - 参数形式：json
*/
public String postJson(String url, String param, String token) {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.set("token", token);
HttpEntity<String> entity = new HttpEntity<>(param, headers);
ResponseEntity<CodeResult> response = restTemplate.postForEntity(url, entity, CodeResult.class);
return parseCodeResult(response);
}
/**
* 解析云端服务接口返回值
*/
public String parseCodeResult(ResponseEntity<CodeResult> response) {
if (response.getStatusCodeValue() != HttpStatus.OK.value()) {
throw new RuntimeException("网络请求失败,状态码:" + response.getStatusCodeValue());
}
CodeResult codeResult = response.getBody();
assert codeResult != null;
if (!codeResult.getSuccess()) {
log.error("调用后台服务接口错误,返回值:{}", JSON.toJSON(codeResult));
throw new RuntimeException("调用后台服务接口错误， 错误信息：" + codeResult.getMsg());
}
return JSON.toJSONString(codeResult.getData());
}
}
三、源码地址
https://github.com/lysmile/spring-boot-demo/tree/master/spring-boot-resttemplate-demo
