Spring Boot发送GET/POST请求——RestTemplate的基本使用

一般我们的Spring Boot工程都是被请求的一方，但某些情况下我们也需要调用别人的接口以实现逻辑，传统情况下在java代码里访问restful服务，一般使用Apache的HttpClient。不过此种方法使用起来太过繁琐，而Spring提供了一种简单便捷的模板类来进行操作，这就是RestTemplate。

RestTemplate是Spring用于同步client端的核心类，简化了与http服务的通信，并满足RestFul原则，程序代码可以给它提供URL，并提取结果。默认情况下，RestTemplate默认依赖jdk的HTTP连接工具。当然你也可以 通过setRequestFactory属性切换到不同的HTTP源，比如Apache HttpComponents、Netty和OkHttp。
Spring启动器中内置了RestTemplate，无需引入其他依赖，只需要spring-boot-starter-web即可。

<!--spring boot启动器-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

1. RestTemplateConfig配置类

@Configuration
public class ResTemplateConfig {
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
return new RestTemplate(factory);
}

@Bean
public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
//超时设置
factory.setReadTimeout(5000);//ms
factory.setConnectTimeout(15000);//ms
return factory;
}
}

2. RestTemplateTest测试类

将RestTemplate对象注入

@RunWith(SpringRunner.class)
@SpringBootTest
public class RestTemplateTest {
@Autowired
private RestTemplate restTemplate;
}

3. 发送GET请求

@Test
public void RestTemplateTestGet() {
/**
* getForObject
* 参数1 要请求的地址的url 必填项
* 参数2 响应数据的类型 是String 还是 Map等 必填项
* 参数3 请求携带参数 选填
* getForObject 方法的返回值就是 被调用接口响应的数据
*/
String url = "http://localhost:5000/users/1";

//1. getForObject()
//先获取返回的字符串，若想获取属性，可以使用gson转化为实体后get方法获取
String result = restTemplate.getForObject(url, String.class);
System.out.println(result);//{"code":"0","data":{"address":"北京市海淀区","id":1,"password":"123456","role":0,"sex":0,"telephone":"10086","username":"小明"},"msg":"操作成功"}

//2. getForEntity()
//获取实体ResponseEntity，可以用get函数获取相关信息
ResponseEntity<String> responseEntity = restTemplate.getForEntity(url, String.class);
System.out.println("responseEntity.getStatusCode() = " + responseEntity.getStatusCode());

System.out.println("responseEntity.getStatusCodeValue() = " + responseEntity.getStatusCodeValue()); //responseEntity.getStatusCodeValue() = 200

System.out.println("responseEntity.getBody() = " + responseEntity.getBody()); //responseEntity.getBody() = {"code":"0","data":{"address":"北京市海淀区","id":1,"password":"123456","role":0,"sex":0,"telephone":"10086","username":"小明"},"msg":"操作成功"}

System.out.println("responseEntity.getHeaders() = " + responseEntity.getHeaders());//responseEntity.getHeaders() = [Content-Type:"application/json", Content-Length:"158", Server:"Werkzeug/0.14.1 Python/3.7.0", Date:"Sat, 16 Oct 2021 06:01:26 GMT"]

System.out.println("responseEntity.getClass() = " + responseEntity.getClass());//responseEntity.getClass() = class org.springframework.http.ResponseEntity

}

4. 发送POST请求

@Test
public void RestTemplateTestPost() {
//String url = "http://127.0.0.1:5000/register";
String url = "http://127.0.0.1:5000/login";

//LinkedMultiValueMap一个键对应多个值，对应format-data的传入类型
LinkedMultiValueMap<String, String> request = new LinkedMultiValueMap<>();
//入参
request.set("username","baihui");
request.set("password", "123456");
request.set("sex", "0");
request.set("telephone", "13172724946");
//请求
String result = restTemplate.postForObject(url,request,String.class);
System.out.println(result);

ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, request, String.class);
System.out.println("responseEntity.getBody() = " + responseEntity.getBody());
}

5. POST发送文件

@Test
public void RestTemplateTestUpload() throws IOException {
String httpMethod = "http://127.0.0.1:5555/photo";
String args = "可以添加其他属性参数";

MultiValueMap<String, Object> paramMap = new LinkedMultiValueMap<>();
paramMap.add("args", args);

//打开图片并写入流
File file=new File("D:\WorkProject\static\output\04.png");
byte[] bytesArray = new byte[(int) file.length()];

FileInputStream fis = new FileInputStream(file);
fis.read(bytesArray); //read file into bytes[]
fis.close();

ByteArrayResource contentsAsResource = new ByteArrayResource(bytesArray) {
//重载设置文件名
@Override
public String getFilename() {
return "04.png";
}
};
paramMap.add("file", contentsAsResource);
String result = restTemplate.postForObject(httpMethod,paramMap,String.class);
System.out.println("result = " + result);
}