HttpClient4.2 Fluent API学习

相比于HttpClient 之前的版本，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只暴露了一些最基本的HttpClient功能。这样，Fluent API就将开发者从连接管理、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。

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还是利用具体例子来说明吧。

以下是几个使用Fluent API的代码样例：

一、最基本的http请求功能

执行Get、Post请求，不对返回的响应作处理

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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 {

//执行一个GET请求,同时设置Timeout参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版本协议执行一个POST请求，同时配置Expect-continue handshake达到性能调优,

//请求中包含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();

//通过代理执行一个POST请求并添加一个自定义的头部属性,请求包含一个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(),
Charset.forName("UTF-8"))

.execute().saveContent(new File("result.dump"));

}

}

二、在后台线程中异步执行多个请求

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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>>();

// 异步执行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、更快速地启动请求

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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。

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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);

}

}