Httpclient实现RPC

HttpClient简介
Get方法请求
Post方式请求
通用类封装

一.HttpClient简介
HttpClient是Apache jakarta common下维护的子项目，封装在 commons-httpclient    jar包中，是一个能提供高效、功能丰富的支持http协议的客户端工具包，在java中的应用主要体现在模拟客户端请求，例如同其他系统或项目进行API数据的交互等，同时也是RPC的实现方式之一。为解决并发量大问题，建议升级到高版本，如4.0以上
maven项目直接引入jar依赖

<!-- HttpClient依赖 -->
<dependency>
<groupId>commons-httpclient</groupId>
<artifactId>commons-httpclient</artifactId>
<version>3.1</version>
</dependency>

二.Get方式请求
Get方式请求主要分为以下步骤：
1、创建客户端

HttpClient  client = new HttpClient();

2、创建Get方式连接实例 

GetMethod  getMethod = new GetMethod(url);

3、execute方法执行方法实例 

client.executeMethod(getMethod);

4、读取响应response信息 

getMethod.getResponseBody()

5、处理获取到的response信息并释放连接 

method.releaseConnection();

三.Post方式请求
HttpClient基于post方式请求步骤基本同Get方式，除了

PostMethod method = new PostMethod(url);

四.通用类的封装（使用 MultiThreadedHttpConnectionManager类管理httpclient是为了解决多线程下并发访问的问题） 

public class HttpClientUtils {

private static Logger log = LoggerFactory.getLogger(HttpClientUtils.class);

private static final String ENCODING = "UTF-8";

private static final int CONNECTION_TIME_OUT = 3000;

private static final int SO_TIME_OUT = 5000;

private static final boolean STALE_CHECK_ENABLED = true;

private static final boolean TCP_NO_DELAY = true;

private static final int DEFAULT_MAX_CONNECTIONS_PER_HOST = 100;

private static final int MAX_TOTAL_CONNECTIONS = 1000;

private static final HttpConnectionManager connectionManager;

private static final HttpClient client;

static {
HttpConnectionManagerParams params = loadHttpConfFromFile();

connectionManager = new MultiThreadedHttpConnectionManager();

connectionManager.setParams(params);

client = new HttpClient(connectionManager);
}

private static HttpConnectionManagerParams loadHttpConfFromFile() {  //这几个参数很重要
HttpConnectionManagerParams params = new HttpConnectionManagerParams();
params.setConnectionTimeout(CONNECTION_TIME_OUT);  //连接超时时长
params.setStaleCheckingEnabled(STALE_CHECK_ENABLED);   //是否启用旧连接检查
params.setTcpNoDelay(TCP_NO_DELAY);
params.setSoTimeout(SO_TIME_OUT);                //读取数据超时时长
params.setDefaultMaxConnectionsPerHost(DEFAULT_MAX_CONNECTIONS_PER_HOST);  //由MultiThreadedHttpConnectionManager管理的最大连接数
params.setMaxTotalConnections(MAX_TOTAL_CONNECTIONS);    //最大连接数
params.setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(0, false));
return params;
}

public static String post(String url, String encoding, String content) {
try {
byte[] resp = post(url, content.getBytes(encoding));
if (null == resp)
return null;
return new String(resp, encoding);
} catch (UnsupportedEncodingException e) {
log.error(e.toString());
return null;
}
}

public static byte[] post(String url, byte[] content) {
try {
byte[] ret = post(url, new ByteArrayRequestEntity(content));
return ret;
} catch (Exception e) {
log.error(e.toString());
return null;
}
}

public static byte[] post(String url, RequestEntity requestEntity)
throws Exception {
PostMethod method = new PostMethod(url);
method.addRequestHeader("Connection", "Keep-Alive");              //这个参数也很重要
method.getParams().setCookiePolicy(CookiePolicy.IGNORE_COOKIES);
method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(0, false));
method.setRequestEntity(requestEntity);
method.addRequestHeader("Content-Type", "application/x-www-form-urlencoded");
try {
int statusCode = client.executeMethod(method);
if (statusCode != HttpStatus.SC_OK) {
return null;
}
return method.getResponseBody();
} catch (SocketTimeoutException e) {
log.error(e.toString());
return null;
} catch (Exception e) {
log.error(e.toString());
return null;
} finally {
if (method != null) {
method.releaseConnection();
}
}
}

public static String doPostByContentType(String url, String contentType, String content) throws Exception {
PostMethod method = new PostMethod(url);
method.addRequestHeader("Connection", "Keep-Alive");
method.getParams().setCookiePolicy(CookiePolicy.IGNORE_COOKIES);
method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(0, false));
method.setRequestEntity(new ByteArrayRequestEntity(content.getBytes(ENCODING)));
method.addRequestHeader("Content-Type", contentType);

try {
int statusCode = client.executeMethod(method);
if (statusCode != HttpStatus.SC_OK) {
return null;
}
byte[] ret = method.getResponseBody();
if (ret == null)
return null;
return new String(ret, ENCODING);
} catch (SocketTimeoutException e) {
log.error(e.toString());
return null;
} catch (Exception e) {
log.error(e.toString());
return null;
} finally {
if (method != null) {
method.releaseConnection();
}
}
}

public static String doGet(String _url) {
try {
GetMethod getMethod = new GetMethod(_url);
client.executeMethod(getMethod);
return inputStream2String(getMethod.getResponseBodyAsStream());
} catch (Exception e) {
e.printStackTrace();
log.error(e.toString());
return null;
}
}

public static String doGetUrl(String _url) throws Exception {
GetMethod getMethod = new GetMethod(_url);
client.executeMethod(getMethod);
return inputStream2String(getMethod.getResponseBodyAsStream());
}

private static String inputStream2String(InputStream is) throws IOException {
BufferedReader in = new BufferedReader(new InputStreamReader(is));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = in.readLine()) != null) {
buffer.append(line);
}
return buffer.toString();
}

private static String inputStream2String(InputStream is, String encoding) throws IOException {
BufferedReader in = new BufferedReader(new InputStreamReader(is, encoding));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = in.readLine()) != null) {
buffer.append(line);
}
return buffer.toString();
}

}

//调用方

StringBuilder sb = new StringBuilder("xxx.xxx.com");
sb.append("?applt=").append(applt).a
c4f7
ppend("&token=").append(token);
HttpClientUtils.doGet(sb.toString());

使用httpclient一定要要根据实际项目场景正确设置上面那几个参数，不然会有风险的。如并发量大时连接池不够、请求等待等风险，这些是比较难测试出来的 .