java怎么用httpclient调用第三方接口，详细代码

以下是使用Httpclient调用第三方接口的详细代码：

1. 引入Httpclient库

首先需要在项目中引入Httpclient库，可以在Maven中添加如下依赖：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.12</version>
</dependency>

2. 创建HttpClient对象

CloseableHttpClient httpClient = HttpClients.createDefault();

3. 创建请求对象

String url = "http://api.xxx.com/user/info";
HttpPost httpPost = new HttpPost(url);

这个例子中，我们发送的请求是POST请求，URL是"http://api.xxx.com/user/info"。

4. 设置请求参数

如果发送POST请求，需要设置请求参数。我们可以创建一个List<NameValuePair>来存储参数，例如：

List<NameValuePair> formParams = new ArrayList<>();
formParams.add(new BasicNameValuePair("username", "test"));
formParams.add(new BasicNameValuePair("password", "123456"));

这个例子中，我们设置了两个参数，一个是"username"，值为"test"，另一个是"password"，值为"123456"。

然后将参数设置到请求对象中：

UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(formParams, "UTF-8");
httpPost.setEntity(formEntity);

5. 发送请求并获取响应

CloseableHttpResponse response = httpClient.execute(httpPost);
try {
    HttpEntity entity = response.getEntity();
    String result = EntityUtils.toString(entity, "UTF-8");
    // 处理响应结果
} finally {
    response.close();
}

首先通过httpClient的execute方法发送请求，得到响应对象response。在finally里将响应对象关闭，释放链接。

然后通过HttpEntity中的EntityUtils将响应实体entity转换成字符串类型，供后续处理。

6. 处理响应结果

得到响应结果之后，我们需要根据第三方接口的具体情况来做不同的处理。例如，如果第三方接口返回的是JSON数据，我们可以通过Jackson库将JSON字符串转换成POJO对象，例如：

ObjectMapper objectMapper = new ObjectMapper();
User user = objectMapper.readValue(result, User.class);

这个例子中，我们将响应结果result转换成了一个User对象。

7. 完整代码

import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

public class HttpClientUtil {

    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();

        String url = "http://api.xxx.com/user/info";
        HttpPost httpPost = new HttpPost(url);

        List<NameValuePair> formParams = new ArrayList<>();
        formParams.add(new BasicNameValuePair("username", "test"));
        formParams.add(new BasicNameValuePair("password", "123456"));

        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(formParams, "UTF-8");
        httpPost.setEntity(formEntity);

        CloseableHttpResponse response = httpClient.execute(httpPost);
        try {
            HttpEntity entity = response.getEntity();
            String result = EntityUtils.toString(entity, "UTF-8");

            // 处理响应结果
            ObjectMapper objectMapper = new ObjectMapper();
            User user = objectMapper.readValue(result, User.class);
            System.out.println(user);
        } finally {
            response.close();
        }
    }

    public static class User {
        private String username;
        private String password;

        // getter, setter
    }
}