Apache的HttpClient，封装工具类

引入依赖

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.13</version>
        </dependency>

1、GET方法

    public static String doGet(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        URIBuilder uriBuilder;
        CloseableHttpResponse httpResponse = null;
        try {
            uriBuilder = new URIBuilder(url);
            if(params != null) {
                params.forEach((k, v) -> {
                    uriBuilder.addParameter(k, v);
                });
            }
            URI uri = uriBuilder.build();
            HttpGet httpGet = new HttpGet(uri);
            httpResponse = client.execute(httpGet);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

2、 POST方法

  public static String doPost(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        try {
            HttpPost httpPost = new HttpPost(url);
            if(params != null) {
                List<NameValuePair> nvpList = new ArrayList<>();
                params.forEach((k, v) -> {
                    nvpList.add(new BasicNameValuePair(k, v));
                });
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(nvpList, Charset.defaultCharset());
                httpPost.setEntity(entity);
            }
            httpResponse = client.execute(httpPost);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

3、application/json方式传参

    public static String doPostJson(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        try {
            HttpPost httpPost = new HttpPost(url);
            if(params != null) {
                StringEntity entity = new StringEntity(JSON.toJSONString(params), ContentType.APPLICATION_JSON);
                httpPost.setEntity(entity);
            }
            httpResponse = client.execute(httpPost);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

贴上完整工具类

import com.alibaba.fastjson.JSON;
import net.jcip.annotations.ThreadSafe;
import org.apache.http.NameValuePair;
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.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
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.io.IOException;
import java.net.URI;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@ThreadSafe
public class HttpClient {

    public static String doGet(String url) {
       return doGet(url, null);
    }

    public static String doGet(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        URIBuilder uriBuilder;
        CloseableHttpResponse httpResponse = null;
        try {
            uriBuilder = new URIBuilder(url);
            if(params != null) {
                params.forEach((k, v) -> {
                    uriBuilder.addParameter(k, v);
                });
            }
            URI uri = uriBuilder.build();
            HttpGet httpGet = new HttpGet(uri);
            httpResponse = client.execute(httpGet);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public static String doPost(String url) {
        return doPost(url, null);
    }

    public static String doPost(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        try {
            HttpPost httpPost = new HttpPost(url);
            if(params != null) {
                List<NameValuePair> nvpList = new ArrayList<>();
                params.forEach((k, v) -> {
                    nvpList.add(new BasicNameValuePair(k, v));
                });
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(nvpList, Charset.defaultCharset());
                httpPost.setEntity(entity);
            }
            httpResponse = client.execute(httpPost);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public static String doPostJson(String url, Map<String, String> params) {
        CloseableHttpClient client = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        try {
            HttpPost httpPost = new HttpPost(url);
            if(params != null) {
                StringEntity entity = new StringEntity(JSON.toJSONString(params), ContentType.APPLICATION_JSON);
                httpPost.setEntity(entity);
            }
            httpResponse = client.execute(httpPost);
            return EntityUtils.toString(httpResponse.getEntity(), Charset.defaultCharset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(httpResponse != null) {
                    httpResponse.close();
                }
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

}