HttpClient 报错 java.lang.NoClassDefFoundError

调用 工具类的时候  报错 java.lang.NoClassDefFoundError  ：INSTANCE 

jar 包也没有冲突  在调用执行  HttpClientBuilder.create().build(); 方法时 就会出现 

https://blog.csdn.net/Lshuibobuxing/article/details/90719604

那就是jar包没有导入嘛

你是不是导错了包。没有的话，换这个版本试试。

我给你发一份工具包。

import com.alibaba.fastjson.JSON;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;
import org.apache.commons.io.IOUtils;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
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.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.ContentBody;
import org.apache.http.entity.mime.content.InputStreamBody;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.Iterator;
import java.util.Map;


public class HttpClientUtils {
    private static Logger LOGGER = LoggerFactory.getLogger(HttpClientUtils.class);

    public static String doGet(String url, Map<String, String> params, Map<String, String> headers) throws Exception {
        return doGet(url + (setGetParams(params, false)), headers);
    }

    public static String doGet(String url, Map<String, String> headers) throws Exception {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        try {
            httpClient = HttpClients.createDefault();
            // 创建Http Get请求
            HttpGet httpPost = new HttpGet(url);
            httpPost.setConfig(getRequestConfig());
            if (headers != null) {
                Header[] allHeader = new BasicHeader[headers.size()];
                int i = 0;
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    allHeader[i] = new BasicHeader(entry.getKey(), entry.getValue());
                    i++;
                }
                httpPost.setHeaders(allHeader);
            }
            // 执行http请求
            response = httpClient.execute(httpPost);
            return EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            org.apache.http.client.utils.HttpClientUtils.closeQuietly(response);
        }
    }

    private static String setGetParams(Map<String, String> params, boolean isWH) throws UnsupportedEncodingException {
        StringBuffer param = new StringBuffer();
        int i = 0;
        for (String key : params.keySet()) {
            if (params.get(key) == null)
                continue;
            if (i == 0)
                if (isWH) {
                    param.append("&");
                } else {
                    param.append("?");
                }
            else
                param.append("&");
            param.append(key).append("=").append(urlEncode(String.valueOf(params.get(key))));
            i++;
        }
        return param.toString();
    }

    private static String urlEncode(String value) throws UnsupportedEncodingException {
        return URLEncoder.encode(value, "utf-8");
    }

    public static String doPost(String url, Map<String, Object> params, Map<String, String> headers) throws Exception {
        return doPost(url, params == null ? null : JSON.toJSONString(params), headers);
    }

    public static String doPost(String url, String requestStr, Map<String, String> headers) throws Exception {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        try {
            httpClient = HttpClients.createDefault();
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            httpPost.setConfig(getRequestConfig());
            if (headers != null) {
                Header[] allHeader = new BasicHeader[headers.size()];
                int i = 0;
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    allHeader[i] = new BasicHeader(entry.getKey(), entry.getValue());
                    i++;
                }
                httpPost.setHeaders(allHeader);
            }
            // 创建参数列表
            if (!StringUtils.isEmpty(requestStr)) {
                StringEntity entity = new StringEntity(requestStr, "UTF-8");
                httpPost.setEntity(entity);
            }
            // 执行http请求
            response = httpClient.execute(httpPost);
            return EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            org.apache.http.client.utils.HttpClientUtils.closeQuietly(response);
        }
    }

    public static String doPostFile(String url, Map<String, String> paramMap, Map<String, String> headers, MultipartFile file) throws Exception {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        try {
            httpClient = HttpClients.createDefault();
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            if (headers != null) {
                Header[] allHeader = new BasicHeader[headers.size()];
                int i = 0;
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    allHeader[i] = new BasicHeader(entry.getKey(), entry.getValue());
                    i++;
                }
                httpPost.setHeaders(allHeader);
            }

            MultipartEntityBuilder mEntityBuilder = MultipartEntityBuilder.create();
            if (paramMap != null && !paramMap.isEmpty()) {
                Iterator<String> iterator = paramMap.keySet().iterator();

                while (iterator.hasNext()) {
                    String key = iterator.next();
                    mEntityBuilder.addPart(key, new StringBody(paramMap.get(key), ContentType.TEXT_PLAIN));
                }
            }
            ContentType contentType = ContentType.create(file.getContentType());
            ContentBody ContentBody = new InputStreamBody(file.getInputStream(), contentType, file.getOriginalFilename());
            mEntityBuilder.addPart("file", ContentBody);
            httpPost.setEntity(mEntityBuilder.build());
            response = httpClient.execute(httpPost);
            return EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            org.apache.http.client.utils.HttpClientUtils.closeQuietly(response);
        }
    }

    private static RequestConfig getRequestConfig() {
        return RequestConfig.custom().setConnectTimeout(10 * 1000) //连接超时时间
                .setConnectionRequestTimeout(1000) //从连接池中取的连接的最长时间
                .setSocketTimeout(10 * 1000) //数据传输的超时时间
                .build();
    }

    public static byte[] downloadFile(String url) throws Exception {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        InputStream in = null;
        try {
            httpClient = HttpClients.createDefault();
            HttpGet httpGet = new HttpGet(url);

            response = httpClient.execute(httpGet);
            HttpEntity entity = response.getEntity();
            in = entity.getContent();

            long length = entity.getContentLength();
            if (length <= 0) {
                return null;
            }
            return IOUtils.toByteArray(in);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            org.apache.http.client.utils.HttpClientUtils.closeQuietly(response);
        }
    }

    public static String sendPost(String url, Map<String, String> params) {
        String send_url = url;
        LOGGER.info("sendUrl:" + send_url + "\t\tparams:" + params);
        PostMethod post = new PostMethod(send_url);
        String result = null;
        try {
            post.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 1000 * 60 * 10);
            setPostParams(post, params);
            result = send(post);
            LOGGER.info("result:" + result);
        } catch (Exception e) {
            LOGGER.error("", e);
            throw new RuntimeException(e);
        } finally {
            post.releaseConnection();// 释放连接
        }
        return result;
    }

    /**
     * 发送请求
     *
     * @param method
     * @return
     * @throws IOException
     */
    private static String send(HttpMethod method) throws IOException {
        HttpClient httpClient = new HttpClient();
        httpClient.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "utf-8");
        httpClient.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 1000 * 60 * 10);

        httpClient.executeMethod(method);
        String s = null;
        try {
            s = method.getResponseBodyAsString();
        } catch (Exception e) {
            LOGGER.error("", method.getURI());
            throw new RuntimeException(e);
        }
        return s;
    }


    /**
     * 设置post参数
     *
     * @param method
     * @param params
     * @throws UnsupportedEncodingException
     */
    public static void setPostParams(PostMethod method, Map<String, String> params) throws UnsupportedEncodingException {
        if (params != null) {
            for (Iterator<String> tor = params.keySet().iterator(); tor.hasNext(); ) {
                String key = tor.next();
                String value = params.get(key) == null ? "" : String.valueOf(params.get(key));
                method.addParameter(key, value);
            }
        }
    }
}

您好，我是有问必答小助手，您的问题已经有小伙伴解答了，您看下是否解决，可以追评进行沟通哦~

如果有您比较满意的答案 / 帮您提供解决思路的答案，可以点击【采纳】按钮，给回答的小伙伴一些鼓励哦～～

ps:问答VIP仅需29元，即可享受5次/月 有问必答服务，了解详情>>>https://vip.csdn.net/askvip?utm_source=1146287632

非常感谢您使用有问必答服务，为了后续更快速的帮您解决问题，现诚邀您参与有问必答体验反馈。您的建议将会运用到我们的产品优化中，希望能得到您的支持与协助！

速戳参与调研>>>https://t.csdnimg.cn/Kf0y

除了引入了httpclient的包，还有哪些其他的包，把你的pom.xml文件里面的依赖贴出来看下。