Cannot instantiate the type HttpClient问题（转）

Posted 2020-08-14 wEndu

看自己动手写爬虫，没想到一上来就跪了。

里面提到用的jar包是apache的http客户端开源项目---HttpClient

就去官网下载了一个版本4.3

当按书上代码敲时

HttpClient httpclient = new HttpClient();

敲完这句，就给跪了

提示Cannot instantiate the type HttpClient，

google 了下，在stackoverflow上面说是应该

HttpClient httpclient = new DefaultHttpClient();

这样写，不过得先import org.apache.http.impl.client.DefaultHttpClient;

试了一下。。。果然可以，但是后面的GetMethod啥的都有，

最后才特么发现从4.×版本后，它的用法就变了不能这么使用了

给个官网示例看看就知道咋回事了

package spider;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class Spider {
    public static void main(String[] args) throws Exception{
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try{
            String url = "http://www.baidu.com";
            HttpGet httpGet = new HttpGet(url);
            System.out.println("executing request " + httpGet.getURI());
            
            ResponseHandler<String> responseHandler = new ResponseHandler<String>(){
                public String handleResponse(final HttpResponse response) throws ClientProtocolException,IOException{
                    int status = response.getStatusLine().getStatusCode();
                    if (status >= 200 && status < 300){
                        HttpEntity entity = response.getEntity();
                        return entity !=null ? EntityUtils.toString(entity) : null;
                    }else{
                        throw new ClientProtocolException("Unexpected response status: " + status);
                    }
                }
            };
            String responseBody = httpclient.execute(httpGet,responseHandler);
            System.out.println("-------------------------------------------");
            System.out.println(responseBody);
            System.out.println("-------------------------------------------");
        }finally{
            httpclient.close();
        }
    }
}