使用httpclient发送http请求

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.3</version>
</dependency>

package com.openapi.TestPojo;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpUriRequest;
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;

public class SimpleHttpClient {
    
    public static String post(String url, Map<String,String> params) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(url);
        List<NameValuePair> nvps = new ArrayList<NameValuePair>();
        Set<String> keySet = params.keySet();
        for(String key : keySet) {
            nvps.add(new BasicNameValuePair(key, params.get(key)));
        }
        httpPost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));
        String body = invoke(httpclient, httpPost);
        try {
            httpclient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return body;
    }
    
    public static String get(String url) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpGet httpGet = new HttpGet(url);
        String body = invoke(httpclient, httpGet);
        try {
            httpclient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return body;
    }
    
    public static String invoke(CloseableHttpClient httpclient, HttpUriRequest request) {
        CloseableHttpResponse response = null;
        try {
            response = httpclient.execute(request);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        HttpEntity entity = response.getEntity();
        String body = null;
        try {
            body = EntityUtils.toString(entity);
        } catch (ParseException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return body;
    }
    
}