HttpClient4.2 Fluent API学习

                相比于HttpClient 之前的版本号，HttpClient 4.2 提供了一组基于流接口(fluent interface)概念的更易使用的API，即Fluent API.

                为了方便使用，Fluent API仅仅暴露了一些最主要的HttpClient功能。

这样，Fluent API就将开发人员从连接管理、资源释放等繁杂的操作中解放出来，从而更易进行一些HttpClient的简单操作。

(原文地址:http://blog.csdn.net/vector_yi/article/details/24298629转载请注明出处)

                还是利用详细样例来说明吧。

下面是几个使用Fluent API的代码例子：

一、最主要的http请求功能

运行Get、Post请求，不正确返回的响应作处理

package com.vectoryi.fluent;

import java.io.File;

import org.apache.http.HttpHost;
import org.apache.http.HttpVersion;
import org.apache.http.client.fluent.Form;
import org.apache.http.client.fluent.Request;
import org.apache.http.entity.ContentType;


public class FluentRequests {

    public static void main(String[] args)throws Exception {
    	//运行一个GET请求,同一时候设置Timeout參数并将响应内容作为String返回
        Request.Get("http://blog.csdn.net/vector_yi")
                .connectTimeout(1000)
                .socketTimeout(1000)
                .execute().returnContent().asString();

        //以Http/1.1版本号协议运行一个POST请求，同一时候配置Expect-continue handshake达到性能调优,
        //请求中包括String类型的请求体并将响应内容作为byte[]返回
        Request.Post("http://blog.csdn.net/vector_yi")
                .useExpectContinue()
                .version(HttpVersion.HTTP_1_1)
                .bodyString("Important stuff", ContentType.DEFAULT_TEXT)
                .execute().returnContent().asBytes();


        //通过代理运行一个POST请求并加入一个自己定义的头部属性,请求包括一个HTML表单类型的请求体
        //将返回的响应内容存入文件
        Request.Post("http://blog.csdn.net/vector_yi")
                .addHeader("X-Custom-header", "stuff")
                .viaProxy(new HttpHost("myproxy", 8080))
                .bodyForm(Form.form().add("username", "vip").add("password", "secret").build())
                .execute().saveContent(new File("result.dump"));
    }

}

二、在后台线程中异步运行多个请求

package com.vectoryi.fluent;

import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import org.apache.http.client.fluent.Async;
import org.apache.http.client.fluent.Content;
import org.apache.http.client.fluent.Request;
import org.apache.http.concurrent.FutureCallback;


public class FluentAsync {

    public static void main(String[] args)throws Exception {
        // 利用线程池
        ExecutorService threadpool = Executors.newFixedThreadPool(2);
        Async async = Async.newInstance().use(threadpool);

        Request[] requests = new Request[] {
                Request.Get("http://www.google.com/"),
                Request.Get("http://www.yahoo.com/"),
                Request.Get("http://www.apache.com/"),
                Request.Get("http://www.apple.com/")
        };


        Queue<Future<Content>> queue = new LinkedList<Future<Content>>();
        // 异步运行GET请求
        for (final Request request: requests) {
            Future<Content> future = async.execute(request, new FutureCallback<Content>() {

                public void failed(final Exception ex) {
                    System.out.println(ex.getMessage() + ": " + request);
                }

                public void completed(final Content content) {
                    System.out.println("Request completed: " + request);
                }

                public void cancelled() {
                }

            });
            queue.add(future);
        }

        while(!queue.isEmpty()) {
            Future<Content> future = queue.remove();
            try {
                future.get();
            } catch (ExecutionException ex) {
            }
        }
        System.out.println("Done");
        threadpool.shutdown();
    }

}

三、更高速地启动请求

package com.vectoryi.fluent;

import org.apache.http.client.fluent.Form;
import org.apache.http.client.fluent.Request;

public class FluentQuickStart {

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

        Request.Get("http://targethost/homepage")
            .execute().returnContent();
        Request.Post("http://targethost/login")
            .bodyForm(Form.form().add("username",  "vip").add("password",  "secret").build())
            .execute().returnContent();
    }
}

四、处理Response

在本例中是利用xmlparsers来解析返回的ContentType.APPLICATION_XML类型的内容。

package com.vectoryi.fluent;

import java.io.IOException;
import java.nio.charset.Charset;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpResponseException;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.fluent.Request;
import org.apache.http.entity.ContentType;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;


public class FluentResponseHandling {

    public static void main(String[] args)throws Exception {
        Document result = Request.Get("http://www.baidu.com")
                .execute().handleResponse(new ResponseHandler<Document>() {

            public Document handleResponse(final HttpResponse response) throws IOException {
                StatusLine statusLine = response.getStatusLine();
                HttpEntity entity = response.getEntity();
                if (statusLine.getStatusCode() >= 300) {
                    throw new HttpResponseException(
                            statusLine.getStatusCode(),
                            statusLine.getReasonPhrase());
                }
                if (entity == null) {
                    throw new ClientProtocolException("Response contains no content");
                }
                DocumentBuilderFactory dbfac = DocumentBuilderFactory.newInstance();
                try {
                    DocumentBuilder docBuilder = dbfac.newDocumentBuilder();
                    ContentType contentType = ContentType.getOrDefault(entity);
                    if (!contentType.equals(ContentType.APPLICATION_XML)) {
                        throw new ClientProtocolException("Unexpected content type:" + contentType);
                    }
                    Charset charset = contentType.getCharset();
                    if (charset == null) {
                        charset = Consts.ISO_8859_1;
                    }
                    return docBuilder.parse(entity.getContent(), charset.name());
                } catch (ParserConfigurationException ex) {
                    throw new IllegalStateException(ex);
                } catch (SAXException ex) {
                    throw new ClientProtocolException("Malformed XML document", ex);
                }
            }

            });
        // 处理得到的result
        System.out.println(result);
    }

}