Java开源框架类库介绍(一)--HttpComponents

我们在开发过程中经常会使用到HTTP协议作为我们数据交换的协议，本小节主要介绍一个开源的HTTP组件的使用。

1. 环境配置

1.1 下载安装

HTTP Components是Apache的一个子项目，地址是： http://hc.apache.org/，主页中提供下载。使用过程及其简单，解压缩后直接将其lib目录下文件拷贝到classpath下即可。

1.2 使用Maven管理

如果您使用Maven管理你的项目，需要这样配置：

		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpclient</artifactId>
			<version>${httpcomponents.version}</version>
		</dependency>
		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpmime</artifactId>
			<version>${httpcomponents.version}</version>
		</dependency>
		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>fluent-hc</artifactId>
			<version>${httpcomponents.version}</version>
		</dependency>

2. 示例代码

2.1 最简单的例子

最简单的例子当然是实现请求的处理，下面分别是GET和POST：

	public void simpleGet() {
		HttpGet get = new HttpGet("http://www.baidu.com");

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(get);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public void simplePost() {
		HttpPost post = new HttpPost("http://www.baidu.com");
		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(post);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

注意我的代码使用了JDK 1.7的try语句块新特性，如果低于1.7版本请自行修改代码。

下面是处理响应的代码：

	private void handleResponse(HttpResponse response) throws IOException {
		int statusCode = 0;
		if ((statusCode = response.getStatusLine().getStatusCode()) == 200) {
			HttpEntity entity = response.getEntity();
			System.out.println(entity.getContentType());
			System.out.println(entity.getContentEncoding());
			System.out.println(entity.getContentLength());

			try (InputStream ins = response.getEntity().getContent();) {
				BufferedReader reader = new BufferedReader(
						new InputStreamReader(ins));
				String str = null;
				while ((str = reader.readLine()) != null) {
					System.out.println(str);
				}
			}
		} else {
			System.out.println("------------http error: statusCode is: "
					+ statusCode);
		}
	}

2.2 增加URI方式

简单的一个请求我们可以处理，那么如果这个请求中需要包含参数呢？下面是代码：

	public void simpleURIGet() throws URISyntaxException {
		URI uri = new URIBuilder().setScheme("http").setHost("www.google.com")
				.setPath("/search").setParameter("q", "httpclient")
				.setParameter("btnG", "Google Search").setParameter("aq", "f")
				.setParameter("oq", "").build();
		HttpGet get = new HttpGet(uri);
		System.out.println(get.getURI());

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(get);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public void simpleURIPost() throws URISyntaxException {
		URI uri = new URIBuilder().setScheme("http").setHost("www.google.com")
				.setPath("/search").setParameter("q", "httpclient")
				.setParameter("btnG", "Google Search").setParameter("aq", "f")
				.setParameter("oq", "").build();
		HttpPost post = new HttpPost(uri);
		System.out.println(post.getURI());

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(post);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

对于POST，还可以这样：

	public void simpleParamPost() throws UnsupportedEncodingException {
		HttpPost post = new HttpPost("http://www.baidu.com");

		List<NameValuePair> params = new ArrayList<>();
		params.add(new BasicNameValuePair("name", "zhangsan"));
		params.add(new BasicNameValuePair("password", "1234"));
		post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(post);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

2.3 对于Header的处理

对于请求头的处理，诸如设置字段值：

	public void addHeadersGet() throws UnsupportedEncodingException {
		HttpGet get = new HttpGet("http://www.baidu.com");
		get.setHeader("User-Agent",
				"Ahopedog/5.0 (Linux NT 5.1; rv:5.0) Gecko/20100101 FireDog/5.0");
		get.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");

		List<NameValuePair> params = new ArrayList<>();
		params.add(new BasicNameValuePair("name", "zhangsan"));
		params.add(new BasicNameValuePair("password", "1234"));

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(get);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public void addHeadersPost() throws UnsupportedEncodingException {
		HttpPost post = new HttpPost("http://www.baidu.com");
		post.setHeader("User-Agent",
				"Ahopedog/5.0 (Linux NT 5.1; rv:5.0) Gecko/20100101 FireDog/5.0");
		post.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");

		List<NameValuePair> params = new ArrayList<>();
		params.add(new BasicNameValuePair("name", "zhangsan"));
		params.add(new BasicNameValuePair("password", "1234"));
		post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(post);) {
			handleResponse(response);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

处理响应头的话基本原理差不多，代码是这样：

	public void handlePostResponseHeader() throws UnsupportedEncodingException {
		HttpPost post = new HttpPost("http://www.baidu.com");

		try (CloseableHttpClient httpClient = new DefaultHttpClient();
				CloseableHttpResponse response = httpClient.execute(post);) {
			Header[] headers = response.getAllHeaders();
			for (Header h : headers) {
				System.out.println(h.getName() + " : " + h.getValue());
			}
			Header serverHeader = response.getFirstHeader("server");
			System.out.println(serverHeader.getName() + " : "
					+ serverHeader.getValue());
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

通过以上代码可以看出，HTTP component能够帮我们省去复杂的HTTP协议的建立连接、处理等操作，框架封装了细节。

3. Fluent方式

以上工作做完了之后，HTTP component仍然觉得不满足，他们认为还可以提供给我们更简洁编写自己代码的方案，于是Fluent来了：

3.1 最简单的调用

GET和POST都差不多：

	public void simpleGet() {
		Request request = Request.Get("http://www.baidu.com");

		handleContent(request);
	}

	public void simplePost() {
		Request request = Request.Post("http://www.baidu.com");

		handleContent(request);
	}

处理代码：

	private void handleContent(Request request) {
		Response response;
		try {
			response = request.execute();
			System.out.println(response.returnContent());
		} catch (ClientProtocolException e1) {
			e1.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

3.2 增加参数

对于GET很简单，这里看看POST：

	public void simpleURIPost() {
		URI uri = URI.create("http://www.sina.com");
		Request request = Request.Post(uri).bodyForm(
				Form.form().add("username", "zhangsan").add("pasword", "pwd")
						.build());

		handleContent(request);
	}

3.3 对于头和整个内容的处理

对于请求头、响应头和整个响应的处理，参见下面的代码：

	public void simpleHeaderPost() {
		Request request = Request.Post("http://www.sina.com.cn");
		request.addHeader("User-Agent",
				"Ahopedog/5.0 (Linux NT 5.1; rv:5.0) Gecko/20100101 FireDog/5.0");
		request.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");

		handleResponse(request);
		handleEntity(request);
	}

	private void handleEntity(Request request) {
		try {
			HttpResponse response = request.execute().returnResponse();
			HttpEntity entity = response.getEntity();
			Header header = entity.getContentType();
			System.out.println(header.getName() + ":    " + header.getValue());
		} catch (ClientProtocolException e1) {
			e1.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	private void handleResponse(Request request) {
		try {
			HttpResponse response = request.execute().returnResponse();
			Header[] headers = response.getAllHeaders();
			for (Header header : headers) {
				System.out.println("Header Name: " + header.getName()
						+ "; Header Value: " + header.getValue());
			}
		} catch (ClientProtocolException e1) {
			e1.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}