Eclipse IDEは `new DefaultHttpClient`の警告を表示し、このクラスを非推奨とマークします。

package com.mkyong.web.controller;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

public class WebCrawler {

    public static void main(String[]args) throws Exception {

        HttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet("/");
        HttpResponse response = client.execute(request);
       //...

    }

}

解決策

ソースコードに潜んで、このコメントを参照してください:

DefaultHttpClient.java

 **  @deprecated (4.3) use {@link HttpClientBuilder}.
 ** /@ThreadSafe
@Deprecated
public class DefaultHttpClient extends AbstractHttpClient {
   //...

これを解決するには、 `HttpClientBuilder`を使います:

package com.hostingcompass.web.controller;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClientBuilder;

public class WebCrawler {

    public static void main(String[]args) throws Exception {

        HttpClient client = HttpClientBuilder.create().build();
        HttpGet request = new HttpGet("/");
        HttpResponse response = client.execute(request);
       //...

    }

}