Java中RestTemplate调用API的几种常用写法

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.14</version>
</dependency>

<!-- 统一使用依赖注入 private final RestTemplate restTemplate; -->

package org.coffeebeans.resttemplate;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.client.RestTemplate;

/**
 * <li>ClassName: RestTemplateConfig </li>
 * <li>Author: OakWang </li>
 */
@Configuration
publicclassRestTemplateConfig {
    @Bean
    public RestTemplate restTemplate() {
        HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory();
        factory.setConnectTimeout(30000); // 连接超时时间（毫秒）
        factory.setReadTimeout(30000); // 读取超时时间（毫秒）
        RestTemplate restTemplate = new RestTemplate(factory);
        MappingJackson2HttpMessageConverterjsonConverter = new MappingJackson2HttpMessageConverter();
        restTemplate.getMessageConverters().add(jsonConverter);// 添加JSON消息转换器
        return restTemplate;
    }
}

String requestUrl = "https://jsonplaceholder.typicode.com/posts/1";
ResponseEntity<String> response = restTemplate.getForEntity(requestUrl, String.class);
if (Objects.equals(HttpStatus.OK, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl = "https://jsonplaceholder.typicode.com/posts/{id}";
ResponseEntity<String> response = restTemplate.getForEntity(requestUrl, String.class, 1); // 参数值为 1
if (Objects.equals(HttpStatus.OK, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl = "https://jsonplaceholder.typicode.com/comments?id={id}&email={email}";
Map<String, Object> params = new HashMap<>();
params.put("id", 1);
params.put("email", "Eliseo@gardner.biz");
ResponseEntity<String> response = restTemplate.getForEntity(requestUrl, String.class, params);
if (Objects.equals(HttpStatus.OK, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl = UriComponentsBuilder.fromHttpUrl("https://jsonplaceholder.typicode.com/posts/1/comments")
        .queryParam("id", "3")
        .queryParam("email", "Nikita@garfield.biz")
        .toUriString();
ResponseEntity<String> response = restTemplate.getForEntity(requestUrl, String.class);
if (Objects.equals(HttpStatus.OK, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl = "https://jsonplaceholder.typicode.com/posts";
ResponseEntity<Object> response = restTemplate.postForEntity(requestUrl, null, Object.class);
if (Objects.equals(HttpStatus.CREATED, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl="https://jsonplaceholder.typicode.com/posts";

List<MyEntity> entityList = new ArrayList<>(); //对象参数
entityList.add(MyEntity.builder().title("foo").body("bar").userId("1").build());
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.set("Authorization", "");
HttpEntity<Object> requestEntity = new HttpEntity<>(entityList, headers);

ResponseEntity<Object> response = restTemplate.postForEntity(requestUrl, requestEntity, Object.class);
if (Objects.equals(HttpStatus.CREATED, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl="https://jsonplaceholder.typicode.com/posts";

Map<String, String> params = new HashMap<>();
params.put("title", "foo");
params.put("body", "bar");
params.put("userId", "1");
MultiValueMap<String, String> form = new LinkedMultiValueMap<>();
for (Map.Entry<String, String> entry : params.entrySet()) {
    form.add(entry.getKey(), entry.getValue());
}
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);

HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(form, headers);
ResponseEntity<Object> response = restTemplate.postForEntity(requestUrl, requestEntity, Object.class);
if (Objects.equals(HttpStatus.CREATED, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}

String requestUrl="https://";
// 1. 初始化参数
Map<String, String> params = new HashMap<>();
params.put("title", "foo");
// 2. 构造 MultiValueMap
MultiValueMap<String, String> form = new LinkedMultiValueMap<>();
for (Map.Entry<String, String> entry : params.entrySet()) {
    form.add(entry.getKey(), entry.getValue());
}
// 3. 设置请求头
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
// 4. 发送请求 返回Object或者指定类型
HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(form, headers);
ResponseEntity<Object> response = restTemplate.postForEntity(requestUrl, requestEntity, Object.class);
//5.处理结果
if (Objects.equals(HttpStatus.OK, response.getStatusCode())) {
    log.info("请求响应结果: {}, {}", requestUrl, response.getBody());
    // 解析...
}