HttpClient 讲解 (1) 基础

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前言

HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet("http://localhost/");
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream instream = entity.getContent();
int l;
byte[] tmp = new byte[2048];
while ((l = instream.read(tmp)) != -1) {
}
}

URI uri = URIUtils.createURI("http", "www.google.com", -1, "/search",
"q=httpclient&btnG=Google+Search&aq=f&oq=", null);
HttpGet httpget = new HttpGet(uri);
System.out.println(httpget.getURI());

List<NameValuePair> qparams = new ArrayList<NameValuePair>();
qparams.add(new BasicNameValuePair("q", "httpclient"));
qparams.add(new BasicNameValuePair("btnG", "Google Search"));
qparams.add(new BasicNameValuePair("aq", "f"));
qparams.add(new BasicNameValuePair("oq", null));
URI uri = URIUtils.createURI("http", "www.google.com", -1, "/search",
URLEncodedUtils.format(qparams, "UTF-8"), null);
HttpGet httpget = new HttpGet(uri);
System.out.println(httpget.getURI());

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());

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);

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\"");
HeaderIterator it = response.headerIterator("Set-Cookie");
while (it.hasNext()) {
System.out.println(it.next());
}

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\"");
HeaderElementIterator it = new BasicHeaderElementIterator(
response.headerIterator("Set-Cookie"));
while (it.hasNext()) {
HeaderElement elem = it.nextElement();
System.out.println(elem.getName() + " = " + elem.getValue());
NameValuePair[] params = elem.getParameters();
for (int i = 0; i < params.length; i++) {
System.out.println(" " + params[i]);
}
}

StringEntity myEntity = new StringEntity("important message",
"UTF-8");
System.out.println(myEntity.getContentType());
System.out.println(myEntity.getContentLength());
System.out.println(EntityUtils.getContentCharSet(myEntity));
System.out.println(EntityUtils.toString(myEntity));
System.out.println(EntityUtils.toByteArray(myEntity).length);

HttpGet httpget = new HttpGet("http://localhost/");
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream instream = entity.getContent();
int byteOne = instream.read();
int byteTwo = instream.read();
// Do not need the rest
httpget.abort();
}

HttpGet httpget = new HttpGet("http://localhost/");
HttpResponse response = httpclient.execute(httpget);
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
}
}

HttpGet httpget = new HttpGet("http://localhost/");
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
if (entity != null) {
entity = new BufferedHttpEntity(entity);
}

File file = new File("somefile.txt");
FileEntity entity = new FileEntity(file, "text/plain; charset=\"UTF-8\"");
HttpPost httppost = new HttpPost("http://localhost/action.do");
httppost.setEntity(entity);

通常来说，HTTP实体需要基于特定的执行上下文来动态地生成。通过使用EntityTemplate实体类和ContentProducer接口，HttpClient提供了动态实体的支持。内容生成器是按照需求生成它们内容的对象，将它们写入到一个输出流中。它们是每次被请求时来生成内容。所以用EntityTemplate创建的实体通常是自我包含而且可以重复的。

ContentProducer cp = new ContentProducer() {
public void writeTo(OutputStream outstream) throws IOException {
Writer writer = new OutputStreamWriter(outstream, "UTF-8");
writer.write("<response>");
writer.write(" <content>");
writer.write(" important stuff");
writer.write(" </content>");
writer.write("</response>");
writer.flush();
}
};
HttpEntity entity = new EntityTemplate(cp);
HttpPost httppost = new HttpPost("http://localhost/handler.do");
httppost.setEntity(entity);

List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("param1", "value1"));
formparams.add(new BasicNameValuePair("param2", "value2"));
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8");
HttpPost httppost = new HttpPost("http://localhost/handler.do");
httppost.setEntity(entity);

StringEntity entity = new StringEntity("important message",
"text/plain; charset=\"UTF-8\"");
entity.setChunked(true);
HttpPost httppost = new HttpPost("http://localhost/acrtion.do");
httppost.setEntity(entity);

HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet("http://localhost/");
ResponseHandler<byte[]> handler = new ResponseHandler<byte[]>() {
public byte[] handleResponse(
HttpResponse response) throws ClientProtocolException, IOException {
HttpEntity entity = response.getEntity();
if (entity != null) {
return EntityUtils.toByteArray(entity);
} else {
return null;
}
}
};
byte[] response = httpclient.execute(httpget, handler);

DefaultHttpClient httpclient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpGet httpget = new HttpGet("http://www.google.com/");
HttpResponse response = httpclient.execute(httpget, localContext);
HttpHost target = (HttpHost) localContext.getAttribute(
ExecutionContext.HTTP_TARGET_HOST);
System.out.println("Final target: " + target);
HttpEntity entity = response.getEntity();
if (entity != null) {
entity.consumeContent();
}

DefaultHttpClient httpclient = new DefaultHttpClient();
HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {
public boolean retryRequest(IOException exception,
int executionCount,HttpContext context) {
if (executionCount >= 5) {
// 如果超过最大重试次数，那么就不要继续了
return false;
}
if (exception instanceof NoHttpResponseException) {
// 如果服务器丢掉了连接，那么就重试
return true;
}
if (exception instanceof SSLHandshakeException) {
// 不要重试SSL握手异常
return false;
}
HttpRequest request = (HttpRequest) context.getAttribute(
ExecutionContext.HTTP_REQUEST);
boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
if (idempotent) {
// 如果请求被认为是幂等的，那么就重试
return true;
}
return false;
}
};
httpclient.setHttpRequestRetryHandler(myRetryHandler);

DefaultHttpClient httpclient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
AtomicInteger count = new AtomicInteger(1);
localContext.setAttribute("count", count);
httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
public void process(final HttpRequest request,
final HttpContext context) throws HttpException, IOException {
AtomicInteger count = (AtomicInteger) context.getAttribute("count");
request.addHeader("Count", Integer.toString(count.getAndIncrement()));
}
});
HttpGet httpget = new HttpGet("http://localhost/");
for (int i = 0; i < 10; i++) {
HttpResponse response = httpclient.execute(httpget, localContext);
HttpEntity entity = response.getEntity();
if (entity != null) {
entity.consumeContent();
}
}

DefaultHttpClient httpclient = new DefaultHttpClient();
httpclient.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION,HttpVersion.HTTP_1_0);
httpclient.getParams().setParameter(CoreProtocolPNames.HTTP_CONTENT_CHARSET,"UTF-8");
HttpGet httpget = new HttpGet("http://www.google.com/");
httpget.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION,HttpVersion.HTTP_1_1);
httpget.getParams().setParameter(CoreProtocolPNames.USE_EXPECT_CONTINUE,Boolean.FALSE);
httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
public void process(final HttpRequest request,
final HttpContext context) throws HttpException, IOException {
System.out.println(request.getParams().getParameter(
CoreProtocolPNames.PROTOCOL_VERSION));
System.out.println(request.getParams().getParameter(
CoreProtocolPNames.HTTP_CONTENT_CHARSET));
System.out.println(request.getParams().getParameter(
CoreProtocolPNames.USE_EXPECT_CONTINUE));
System.out.println(request.getParams().getParameter(
CoreProtocolPNames.STRICT_TRANSFER_ENCODING));
}
});</span>

HttpParams params = new BasicHttpParams();
HttpProtocolParamBean paramsBean = new HttpProtocolParamBean(params);
paramsBean.setVersion(HttpVersion.HTTP_1_1);
paramsBean.setContentCharset("UTF-8");
paramsBean.setUseExpectContinue(true);
System.out.println(params.getParameter(
CoreProtocolPNames.PROTOCOL_VERSION));
System.out.println(params.getParameter(
CoreProtocolPNames.HTTP_CONTENT_CHARSET));
System.out.println(params.getParameter(
CoreProtocolPNames.USE_EXPECT_CONTINUE));
System.out.println(params.getParameter(
CoreProtocolPNames.USER_AGENT));

HttpClient 讲解 (1) 基础

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原文地址：http://blog.csdn.net/u014201191/article/details/49745033