Deprecated Java HttpClient - How hard can it be?

问题

All I'm trying to do is download some JSON and deserialize it into an object. I haven't got as far as downloading the JSON yet.

Almost every single HttpClient example I can find, including those on the apache site looks something like...

import org.apache.http.client.HttpClient;
import org.apache.http.impl.client.DefaultHttpClient;

public void blah() {
    HttpClient client = new DefaultHttpClient();
    ...
}

However, Netbeans tells me that DefaultHttpClient is deprecated. I've tried googling for DefaultHttpClient deprecated and as many other variations as I can think of and can't find any useful results, so I'm obviously missing something.

What is the correct Java7 way to download the contents of a webpage? Is there really no decent Http Client as part of the language? I find that hard to believe.

My Maven dependency for this is...

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>LATEST</version>
    <type>jar</type>
</dependency>

回答1:

Relevant imports:

import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import java.io.IOException;

Usage:

HttpClient httpClient = HttpClientBuilder.create().build();

EDIT (after Jules' suggestion):

As the build() method returns a CloseableHttpClient which is-a AutoClosable, you can place the declaration in a try-with-resources statement (Java 7+):

try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {

    // use httpClient (no need to close it explicitly)

} catch (IOException e) {

    // handle

}

回答2:

IMHO the accepted answer is correct but misses some 'teaching' as it does not explain how to come up with the answer. For all deprecated classes look at the JavaDoc (if you do not have it either download it or go online), it will hint at which class to use to replace the old code. Of course it will not tell you everything, but this is a start. Example:

...
 *
 * @deprecated (4.3) use {@link HttpClientBuilder}.  <----- THE HINT IS HERE !
 */
@ThreadSafe
@Deprecated
public class DefaultHttpClient extends AbstractHttpClient {

Now you have the class to use, HttpClientBuilder, as there is no constructor to get a builder instance you may guess that there must be a static method instead: create. Once you have the builder you can also guess that as for most builders there is a build method, thus:

org.apache.http.impl.client.HttpClientBuilder.create().build();

AutoClosable:

As Jules hinted in the comments, the returned class implements java.io.Closable, so if you use Java 7 or above you can now do:

    try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {...}

The advantage is that you do not have to deal with finally and nulls.

Other relevant info

Also make sure to read about connection pooling and set the timeouts.

回答3:

Examples from Apache use this:

HttpClient httpclient = HttpClients.createDefault();

The class org.apache.http.impl.client.HttpClients is there since version 4.3. The code for HttpClients.createDefault() is the same as the accepted answer in here.

回答4:

It got deprecated in version 4.3-alpha1 which you use because of the LATEST version specification. If you take a look at the javadoc of the class, it tells you what to use instead: HttpClientBuilder.

In the latest stable version (4.2.3) the DefaultHttpClient is not deprecated yet.

回答5:

Try jcabi-http, which is a fluent Java HTTP client, for example:

String html = new JdkRequest("https://www.google.com")
  .header(HttpHeaders.ACCEPT, MediaType.TEXT_HTML)
  .fetch()
  .as(HttpResponse.class)
  .assertStatus(HttpURLConnection.HTTP_OK)
  .body();

Check also this blog post: http://www.yegor256.com/2014/04/11/jcabi-http-intro.html

回答6:

I would suggest using the below method if you are trying to read the json data only.

URL requestUrl=new URL(url);
URLConnection con = requestUrl.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
StringBuilder sb=new StringBuilder();
int cp;
try {
    while((cp=rd.read())!=-1){
    sb.append((char)cp);
  }
 catch(Exception e){
 }
 String json=sb.toString();

回答7:

You could add the following Maven dependency.

    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.1</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpmime -->
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpmime</artifactId>
        <version>4.5.1</version>
    </dependency>

You could use following import in your java code.

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGett;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.client.methods.HttpUriRequest;

You could use following code block in your java code.

HttpClient client = HttpClientBuilder.create().build();
HttpUriRequest httpUriRequest = new HttpGet("http://example.domain/someuri");

HttpResponse response = client.execute(httpUriRequest);
System.out.println("Response:"+response);

回答8:

Use HttpClientBuilder to build the HttpClient instead of using DefaultHttpClient

ex:

MinimalHttpClient httpclient = new HttpClientBuilder().build();

 // Prepare a request object
 HttpGet httpget = new HttpGet("http://www.apache.org/");

回答9:

This is the solution that I have applied to the problem that httpclient deprecated in this version of android 22

 public static String getContenxtWeb(String urlS) {
    String pagina = "", devuelve = "";
    URL url;
    try {
        url = new URL(urlS);
        HttpURLConnection conexion = (HttpURLConnection) url
                .openConnection();
        conexion.setRequestProperty("User-Agent",
                "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)");
        if (conexion.getResponseCode() == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(conexion.getInputStream()));
            String linea = reader.readLine();
            while (linea != null) {
                pagina += linea;
                linea = reader.readLine();
            }
            reader.close();

            devuelve = pagina;
        } else {
            conexion.disconnect();
            return null;
        }
        conexion.disconnect();
        return devuelve;
    } catch (Exception ex) {
        return devuelve;
    }
}

回答10:

For the original issue, I would request you to apply below logic:

 CloseableHttpClient httpClient = HttpClientBuilder.create().build();
 HttpPost httpPostRequest = new HttpPost();

来源：https://stackoverflow.com/questions/15336477/deprecated-java-httpclient-how-hard-can-it-be