httpclient3和httpclient4都有連接池的概念，但兩個版本的接口相差較大。
使用HttpClient發送請求、接收響應很簡單，一般需要如下幾步即可。
1. 創建HttpClient對象。
2. 創建請求方法的實例，並指定請求URL。如果需要發送GET請求，創建HttpGet對象；如果需要發送POST請求，創建HttpPost對象。
3. 如果需要發送請求參數，可調用HttpGet、HttpPost共同的setParams(HetpParams params)方法來添加請求參數；對於HttpPost對象而言，也可調用setEntity(HttpEntity entity)方法來設置請求參數。
4. 調用HttpClient對象的execute(HttpUriRequest request)發送請求，該方法返回一個HttpResponse。
5. 調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭；調用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內容。程序可通過該對象獲取服務器的響應內容。
6. 釋放連接。無論執行方法是否成功，都必須釋放連接
httpclient3
MultiThreadedHttpConnectionManager 是HTTP Client中用來複用連接的連接管理類,可以通過以下方法創建一個client實例
MultiThreadedHttpConnectionManager n = new MultiThreadedHttpConnectionManager();
HttpClient client = new HttpClient(n);
public class HttpClientUtils {
/**
* 日誌處理類
*/
private static final Log logger = LogFactory.getLog(HttpClientUtils.class);
// 讀取超時
private final static int SOCKET_TIMEOUT = 30000;
// 連接超時
private final static int CONNECTION_TIMEOUT = 30000;
// 每個HOST的最大連接數量(連接至目的主機的線程數)
private final static int MAX_CONN_PRE_HOST = 2;
// 連接池的最大連接數(相當於線程數)
private final static int MAX_CONN = 2;
// 連接池
private final static HttpConnectionManager httpConnectionManager;
HttpClient httpClient;
static {
httpConnectionManager = new MultiThreadedHttpConnectionManager();
HttpConnectionManagerParams params = httpConnectionManager.getParams();
params.setConnectionTimeout(CONNECTION_TIMEOUT);
params.setSoTimeout(SOCKET_TIMEOUT);
params.setDefaultMaxConnectionsPerHost(MAX_CONN_PRE_HOST);
params.setMaxTotalConnections(MAX_CONN);
httpClient = new HttpClient(httpConnectionManager);
}
/**
* 發送主要方法,異常捕獲
*
* @param post
* @param code
* @return
*/
public static String doHttpPostRequest(PostMethod post) {
String resultString = "";
try {
httpClient.executeMethod(post);
if (post.getStatusCode() == HttpStatus.SC_OK) {
resultString = post.getResponseBodyAsString();
}
} catch (HttpException e) {
logger.error("http請求超時", e);
} catch (IOException e) {
logger.error("IO超時", e);
} finally {
post.releaseConnection();
}
return resultString;
}
/**
* 設置一下返回錯誤的通用提示,可以自定義格式.
*
* @param reason
* @return
*/
public static String returnError(String reason) {
StringBuffer buffer = new StringBuffer();
buffer.append("<?xml version=\"1.0\" encoding=\"GBK\"?>");
buffer.append("<Response>");
buffer.append("<Success>false</Success>");
buffer.append("<reason>");
buffer.append(reason);
buffer.append("</reason>");
buffer.append("</Response>");
return buffer.toString();
}
public final static String REQUEST_HEADER = "x-forwarded-for";
/**
* 將客戶IP寫入請求頭 這個設置可以僞裝IP請求,注意使用
*
* @param client
* @param ip
* @return
*/
public static void resetRequestHeader(HttpClient client, String ip) {
List<Header> headers = new ArrayList<Header>();
headers.add(new Header(REQUEST_HEADER, ip));
client.getHostConfiguration().getParams().setParameter("http.default-headers", headers);
}
}
public class HttpClientTest {
/**
* 組裝參數,這裏用Map,一鍵一值比較通用,可以當做共用方法
* @param params
* @return
*/
private NameValuePair[] buildNameValuePairs(Map<String, String> params) {
Object[] keys = params.keySet().toArray();
NameValuePair[] pairs = new NameValuePair[keys.length];
for (int i = 0; i < keys.length; i++) {
String key = (String) keys[i];
pairs[i] = new NameValuePair(key, params.get(key));
}
return pairs;
}
/**
* 執行一個HTTP POST請求，返回請求響應的HTML
*
* @param url
* 請求的URL地址
* @param params
* 請求的查詢參數,可以爲null
* @return 返回請求響應的string
*/
public String doPost(String url, Map<String, String> params){
String response = "";
if (null == url || "".equals(url.trim())) {
return HttpClientUtil.returnError("推送地址錯誤[url=" + url + "]");
}
if (null == code || "".equals(code.trim())) {
return HttpClientUtil.returnError("編碼錯誤[code=" + code + "]");
}
if (null == params || params.size() == 0) {
return HttpClientUtil.returnError("無傳遞參數[params.size = 0]");
}
PostMethod postMethod = new PostMethod(url);
postMethod.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "utf-8");
//設置失敗重複提交次數
postMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(5, true));
postMethod.setRequestBody(buildNameValuePairs(params));
response = HttpClientUtils.doHttpPostRequest(postMethod);
return response;
}
public static void main(String[] args) {
String url = "http://localhost/serlvet";
String xml = "xxxxxxxxxxxxxxxxxxxxxxx";
HashMap<String, String> params = new HashMap<String, String>();
params.put("aaaa", xml);
params.put("bbbb", "bbbxxxx");
String r = new HttpClientTest().doPost(url,params);
System.out.println(r);
}
}
public class HttpClientUtils2 implements Runnable{
private static final Log logger = LogFactory.getLog(HttpClientUtils2.class);
private static ThreadSafeClientConnManager cm = null;
static {
int maxTotal = 20;
int defaultMaxConnection = 50;
SchemeRegistry schemeRegistry = new SchemeRegistry();
schemeRegistry.register(new Scheme("http", 80, PlainSocketFactory.getSocketFactory()));
cm = new ThreadSafeClientConnManager(schemeRegistry);
try {
cm.setMaxTotal(maxTotal);
// 每條通道的併發連接數設置（連接池）
cm.setDefaultMaxPerRoute(defaultMaxConnection);
} catch (NumberFormatException e) {
e.printStackTrace();
}
}
public static HttpClient getHttpClient() {
HttpParams params = new BasicHttpParams();
params.setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);
params.setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 30000); // 3000ms
params.setParameter(CoreConnectionPNames.SO_TIMEOUT, 30000); // 3000ms
return new DefaultHttpClient(cm, params);
}
public static void release() {
if (cm != null) {
cm.shutdown();
}
}
public static void doHttpPostRequest(String url) {
InputStream in = null;
HttpResponse response;
HttpClient client = getHttpClient();
try {
response = client.execute(post);
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
HttpEntity entity = response.getEntity();
long l = entity.getContentLength();
//將返回轉換成string（方法1）
in = entity.getContent();
int count = 0;
while (count == 0) {
count = Integer.parseInt(""+entity.getContentLength());//in.available();
}
byte[] bytes = new byte[count];
int readCount = 0; // 已經成功讀取的字節的個數
while (readCount <= count) {
if(readCount == count)break;
readCount += in.read(bytes, readCount, count - readCount);
}
//將返回轉換成string（方法2）
//System.out.println(EntityUtils.toString(entity));
}
if (in != null) {
//關閉連接，否則連接池消耗完
in.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class HttpClient2Test {
/**
* 執行一個HTTP POST請求，返回請求響應的HTML
*
* @param url
* 請求的URL地址
* @param params
* 請求的查詢參數,可以爲null
* @return 返回請求響應的string
*/
public String doPost(String url, Map<String, String> params){
String response = "";
HttpPost post = new HttpPost(url);
// 設置post編碼
post.getParams().setParameter("http.protocol.content-charset", HTTP.UTF_8);
post.getParams().setParameter(HTTP.CONTENT_ENCODING, HTTP.UTF_8);
post.getParams().setParameter(HTTP.CHARSET_PARAM, HTTP.UTF_8);
post.getParams().setParameter(HTTP.DEFAULT_PROTOCOL_CHARSET, HTTP.UTF_8);
try {
post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
} catch (UnsupportedEncodingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
response = HttpClientUtils2.doHttpPostRequest(postMethod);
return response;
}
public static void main(String[] args) {
String url = "http://localhost/serlvet";
String xml = "xxxxxxxxxxxxxxxxxxxxxxx";
// 設置參數
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("abc", "xml"));
String r = new HttpClientTest().doPost(url,params);
System.out.println(r);
}
}