标签：java4android http httpclient
在Java开发中，不可避免的需要和http打交道。而无论我司的迅雷动漫还是我主导的“搜芽”android客户端开发，都需要使用到http和服务器打交道。。虽然Java也提供了http的接口，但据我了解，更多的公司都是使用Apache的httpclient来进行开发，不仅因为它灵活强大，而且便捷。
今天，我们学习httpclient的基础知识。
关于Http的基础，在此就不再复习了。建议大家去看一本权威制作《HTTP权威指南》，加个略贵，109元人民币，不过，我买了，因为经典的书，还是多备一下，我也没怎么看，但遇到问题就翻即可。
闲话少说，切入正题。
我们发出一个http的请求，在httpclient中一般如下流程模式:
1. 创建HttpClient对象。
2. 创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
3. 如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数
4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。
6. 释放连接。无论执行方法是否成功，都必须释放连接.
代码示例如下：
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
<...>
} finally {
response.close();
}
HttpClient支持所有的HTTP/1.1的所有命令，包含：GET，HEAD，POST，PUT，DELETE，TRACE和OPTIONS。而且都有单独对应的类：HttpGet,HttpHead,....等等。
请求URI是统一资源标识符，标识了你所要请求的资源。它一般包含protocol scheme , host name, optional port, resource path,optional query ,optional fragment这些信息。如：
HttpGet httpget = new HttpGet( "http://www.google.com/search?hl=en&q=httpclient&btnG=Google+Search&aq=f&oq=");构造上述URI一个更为好的方法是使用URIBuilder。具体如下：
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 httpget = new HttpGet(uri);
回复（response）是服务器对客户端的回复。httpclient中的回复是HttpResponse.
HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_OK, "OK"); System.out.println(response.getProtocolVersion()); System.out.println(response.getStatusLine().getStatusCode()); System.out.println(response.getStatusLine().getReasonPhrase()); System.out.println(response.getStatusLine().toString());
输出：
HTTP/1.1 200 OK HTTP/1.1 200 OK
如果大家熟悉HTTP包的话，就知道一个HTTP报文是由三个部分组成的：对报文进行描述的起始行(start line），包含属性的首部块（header），以及可选的，包含数据的主体部分（body）。
httpclient的一个关于头部的示例：
HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1,
HttpStatus.SC_OK, "OK");
response.addHeader("Set-Cookie",
"c1=a; path=/; domain=localhost");
response.addHeader("Set-Cookie",
"c2=b; path=\"/\", c3=c; domain=\"localhost\"");
Header h1 = response.getFirstHeader("Set-Cookie");
System.out.println(h1);
Header h2 = response.getLastHeader("Set-Cookie");
System.out.println(h2);
Header[] hs = response.getHeaders("Set-Cookie");
System.out.println(hs.length);Set-Cookie: c1=a; path=/; domain=localhost Set-Cookie: c2=b; path="/", c3=c; domain="localhost" 2
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream instream = entity.getContent();
try {
// do something useful
} finally {
instream.close();
}
}
} finally {
response.close();
}CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
HttpEntity entity = response.getEntity();
if (entity != null) {
long len = entity.getContentLength();
if (len != -1 && len < 2048) {
System.out.println(EntityUtils.toString(entity));
} else {
// Stream content out
}
}
} finally {
response.close();
}File file = new File("somefile.txt");
FileEntity entity = new FileEntity(file,
ContentType.create("text/plain", "UTF-8"));
HttpPost httppost = new HttpP
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("param1", "value1"));
formparams.add(new BasicNameValuePair("param2", "value2"));
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
HttpPost httppost = new HttpPost("http://localhost/handler.do");
httppost.setEntity(entity);会产生如下效果：param1=value1&m2=value2
private InputStream httpGet(String url, String cookie) {
HttpGet httpGet = new HttpGet(url);
httpGet.setHeader("Accept-Encoding", "gzip,deflate");
if (!(TextUtils.isEmpty(cookie))) {
httpGet.setHeader("Cookie", cookie);
}
return httpDo(httpGet, url, null);
}
private InputStream httpPost(String url, Map<String, String> headers,
Map<String, Object> params) {
HttpPost post = new HttpPost(url);
HttpEntity entity = null;
Object value = params.get(POST_ENTITY);
if (value instanceof HttpEntity) {
entity = (HttpEntity) value;
} else {
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
for (Map.Entry<String, Object> e : params.entrySet()) {
value = e.getValue();
if (value != null) {
LOG.debug("param=" + e.getKey() + ":" + value.toString());
pairs.add(new BasicNameValuePair(e.getKey(), value
.toString()));
}
}
try {
entity = new UrlEncodedFormEntity(pairs, "UTF-8");
} catch (UnsupportedEncodingException e1) {
LOG.warn("UnsupportedEncodingException err={}", e1.toString());
}
}
if (headers != null && !headers.containsKey("Content-Type")) {
headers.put("Content-Type",
"application/x-www-form-urlencoded;charset=UTF-8");
}
post.setEntity(entity);
return httpDo(post, url, headers);
}
private InputStream httpDo(HttpUriRequest hr, String url,
Map<String, String> headers) {
InputStream in = null;
if (headers != null) {
for (String name : headers.keySet()) {
hr.addHeader(name, headers.get(name));
}
}
DefaultHttpClient client = getClient();
HttpResponse response;
try {
response = client.execute(hr);
int statusCode = response.getStatusLine().getStatusCode();
LOG.debug("this={}, response code={}", this, statusCode);
if (statusCode == HttpStatus.SC_OK) {
HttpEntity entity = response.getEntity();
if (null != entity) {
Header header = entity.getContentEncoding();
if (header != null && header.getValue().equals("gzip")) {
in = new GZIPInputStream(entity.getContent());
} else {
in = entity.getContent();
}
}
} else {
LOG.warn("Request HTTP resource failed. StatusCode={} Url={}", statusCode, url);
}
} catch (IOException e) {
LOG.warn("Request HTTP resource failed. {}, err={}", this, e.toString());
} catch (IllegalStateException e) {
LOG.warn("Request HTTP resource failed. url={} err={}", url, e.toString());
}
return in;
}
private static DefaultHttpClient getClient() {
HttpParams httpParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParams, CONNECTION_TIMEOUT);
HttpConnectionParams.setSoTimeout(httpParams, SO_TIMEOUT);
// http://stackoverflow.com/questions/5358014/android-httpclient-oom-on-4g-lte-htc-thunderbolt
HttpConnectionParams.setSocketBufferSize(httpParams, 8192);
return new DefaultHttpClient(httpParams);
}
标签：java4android http httpclient
原文地址：http://blog.csdn.net/minimicall/article/details/39158447
