该工具类都是同步请求简单的封装了下OkHttp

maven依赖

<!--fastjson 依赖添加-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.47</version>
</dependency>
<!--log4j 依赖添加-->
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>
<!--slf4j 依赖添加-->
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.2</version>
</dependency>
<!--okhttp3 依赖添加-->
<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>3.6.0</version>
</dependency>
<!--lombok 依赖添加-->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.18</version>
</dependency>

工具类

import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import okhttp3.*;
import okio.BufferedSink;
import okio.Okio;
import java.io.File;
import java.util.HashMap;
import java.util.Map;

@Slf4j
public class OkHttpUtil {

    /**
     * Get请求
     * @param url   URL地址
     * @return  返回结果
     */
    public static String get(String url){
        String result=null;
        try {
            OkHttpClient okHttpClient=new OkHttpClient();
            Request request = new Request.Builder().url(url).build();
            Response response = okHttpClient.newCall(request).execute();
            result=response.body().string();
            log.info("Get请求返回：{}",result);
            return result;
        }catch (Exception e){
            log.error("OkHttp[Get]请求异常",e);
            return result;
        }
    }

    /**
     * Post请求
     * @param url       URL地址
     * @param params    参数
     * @return  返回结果
     */
    public static String post(String url,Map<String,String> params){
        String result=null;
        if (params==null){
            params=new HashMap<String, String>();
        }
        try {
            OkHttpClient okHttpClient=new OkHttpClient();
            FormBody.Builder formBodyBuilder = new FormBody.Builder();
            //添加参数
            log.info("params：{}", JSON.toJSONString(params));
            for (Map.Entry<String,String> map:params.entrySet()){
                String key=map.getKey();
                String value;
                if (map.getValue()==null){
                    value="";
                }else{
                    value=map.getValue();
                }
                formBodyBuilder.add(key,value);
            }
            FormBody formBody =formBodyBuilder.build();
            Request request = new Request.Builder().url(url).post(formBody).build();
            Response response = okHttpClient.newCall(request).execute();
            result=response.body().string();
            log.info("Post请求返回：{}",result);
            return result;
        }catch (Exception e){
            log.error("OkHttp[Post]请求异常",e);
            return result;
        }
    }

    /**
     * 上传文件请求（Post请求）
     * @param url       URL地址
     * @param params    文件 key：参数名 value：文件 （可以多文件）
     * @return  返回结果
     */
    public static String upload(String url, Map<String, File> params){
        String result=null;
        try {
            OkHttpClient okHttpClient=new OkHttpClient();
            MultipartBody.Builder multipartBodyBuilder =new MultipartBody.Builder().setType(MultipartBody.FORM);

            for (Map.Entry<String,File> map:params.entrySet()){
                String key=map.getKey();
                File file=map.getValue();
                if (file==null||(file.exists() && file.length() == 0)){
                    continue;
                }
                multipartBodyBuilder.addFormDataPart(key,file.getName(),RequestBody.create(MediaType.parse("multipart/form-data"), file));
            }
            RequestBody requestBody =multipartBodyBuilder.build();
            Request request = new Request.Builder().url(url).post(requestBody).build();
            Response response = okHttpClient.newCall(request).execute();
            result=response.body().string();
            log.info("Upload请求返回：{}",result);
            return result;
        }catch (Exception e){
            log.error("OkHttp[Upload]请求异常",e);
            return result;
        }
    }

    /**
     * 下载文件请求（Get请求）
     * @param url       URL地址
     * @param savePath  保存路径（包括文件名）
     * @return  文件保存路径
     */
    public static String download(String url,String savePath){
        String result=null;
        try {
            OkHttpClient okHttpClient=new OkHttpClient();
            Request request = new Request.Builder().url(url).build();
            Response response = okHttpClient.newCall(request).execute();
            File file=new File(savePath);
            if (!file.getParentFile().exists()){
                file.getParentFile().mkdirs();
            }
            BufferedSink sink =Okio.buffer((Okio.sink(file)));
            sink.writeAll(response.body().source());
            sink.flush();
            sink.close();
            result=savePath;
            log.info("Download请求返回：{}",result);
            return result;
        }catch (Exception e){
            log.error("OkHttp[Download]请求异常",e);
            return result;
        }
    }

}