API调用Java实战：使用RestTemplate或者HTTPURLConnection

原创小鱼儿 2024-11-08 20:51 3阅读 0赞

在Java中，调用API通常有两种常见的方法：使用`RestTemplate`和使用`HTTPURLConnection`。下面我将分别介绍这两种方法的实战示例。

### 使用RestTemplate`RestTemplate`是Spring框架提供的一个用于同步客户端HTTP访问的类。它简化了与HTTP服务器的通信，并封装了HTTP连接的创建和请求的执行。

####1. 添加依赖如果你使用的是Maven，可以在`pom.xml`文件中添加以下依赖：

```xml<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
```####2. 创建RestTemplate实例```javaimport org.springframework.web.client.RestTemplate;

public class ApiClient {
 private static final String API_URL = "http://api.example.com";

public static void main(String[] args) {
 RestTemplate restTemplate = new RestTemplate();
//调用API }
}
```####3. 发送GET请求```javaString url = API_URL + "/users";
String result = restTemplate.getForObject(url, String.class);
System.out.println(result);
```####4. 发送POST请求```javaString url = API_URL + "/users";
Map<String, Object> requestBody = new HashMap<>();
requestBody.put("name", "John Doe");
requestBody.put("email", "john.doe@example.com");

User user = restTemplate.postForObject(url, requestBody, User.class);
System.out.println(user);
```### 使用HTTPURLConnection`HTTPURLConnection`是Java标准库的一部分，不需要额外的依赖。

####1. 创建连接```javaimport java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;

public class ApiClient {
 private static final String API_URL = "http://api.example.com";

public static void main(String[] args) throws Exception {
URL url = new URL(API_URL + "/users");
 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
 conn.setRequestMethod("GET");
// 设置请求头等 conn.setRequestProperty("Content-Type", "application/json");
// 发送请求int responseCode = conn.getResponseCode();
if (responseCode != HttpURLConnection.HTTP_OK) {
 throw new RuntimeException("Failed : HTTP error code : " + responseCode);
 }
 BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String inputLine;
 StringBuffer response = new StringBuffer();

while ((inputLine = in.readLine()) != null) {
 response.append(inputLine);
 }
in.close();

//打印结果 System.out.println(response.toString());
 }
}
```####2. 发送POST请求```javaString url = API_URL + "/users";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();

con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/json");
con.setRequestProperty("Accept", "application/json");

String urlParameters = "{\"name\":\"John Doe\",\"email\":\"john.doe@example.com\"}";

con.setDoOutput(true);
OutputStream os = con.getOutputStream();
os.write(urlParameters.getBytes());
os.flush();
os.close();

int responseCode = con.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
 BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
 StringBuffer response = new StringBuffer();

while ((inputLine = in.readLine()) != null) {
 response.append(inputLine);
 }
in.close();

//打印结果 System.out.println(response.toString());
} else {
 System.out.println("POST request not worked");
}
```这两种方法各有优缺点，`RestTemplate`更简单易用，适合快速开发；而`HTTPURLConnection`更底层，适合需要更精细控制的场景。根据你的具体需求选择合适的方法。