我们做web开发时，需要经常使用httpclient来请求http服务，有时为了安全起见，服务提供方会提供多个http地址，这样如果我们请求某个ip出现异常，可以重试其他的ip地址，来尽量保证系统的稳定，以下是自定义一个HttpMethod重试机制的简要代码。

HostCluster类定义需要连接的协议、ips[]、重试次数、随机获取一个host等：

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ClusterRetryHttpMethod从HostCluster获取的randomHost，然后new URI()设置相应的base（GetMethod or PostMethod）

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public abstract class ClusterRetryHttpMethod<T extends HttpMethod> {
protected HostCluster cluster;
protected String urlSuffix;
protected T base;
private Integer retry;
public ClusterRetryHttpMethod(HostCluster cluster, String urlSuffix) {
this(cluster, urlSuffix, null);
}
public ClusterRetryHttpMethod(HostCluster cluster, String urlSuffix, Integer retry) {
if (cluster == null || StringUtils.isBlank(urlSuffix)) {
throw new IllegalArgumentException(\"invalid params.\");
}
if (retry != null) {
if (retry < 0) {
throw new IllegalArgumentException(\"invalid retry.\");
} else {
this.retry = retry;
}
}
this.cluster = cluster;
this.urlSuffix = urlSuffix;
this.base = initBase();
}
public boolean isHttps() {
return this.cluster.isHttps();
}
public void setQueryString(String queryString) {
this.base.setQueryString(queryString);
}
public void setQueryString(NameValuePair[] params) {
this.base.setQueryString(params);
}
public int getRetry() {
return retry == null ? this.cluster.getRetry() : retry;
}
protected abstract T initBase();//子类各自实现，GetMethod or PostMethod
public T randomMethod() throws Exception {
String url = this.randomUrl();
if (StringUtils.isBlank(url)) {
url = \"/\";
}
this.base.setURI(new URI(url, true));
return base;
}
protected String randomUrl() {
return cluster.randomHost() + urlSuffix;
}
}

最后就是怎么调用了，这里使用的是HttpClientPool来调用http连接，关于HttpClientPool详见我的另一篇文章：http://blog.itpub.net/28912557/viewspace-1223241/

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public class HttpClientPool extends GenericObjectPool<HttpClient> {
private int httpsPort;
public HttpClientPool(PoolableObjectFactory<HttpClient> factory) {
super(factory);
}
public <T> T doPost(ClusterRetryHttpMethod method, HttpClientDataCallback<T> callback) {
HttpClient toUse = null;
HttpMethod m = null;
int index = 0;
if (method == null) {
return null;
}
if (method.isHttps()) {
Protocol myhttps = new Protocol(\"https\", new SSLProtocolSocketFactoryImpl(), httpsPort);
Protocol.registerProtocol(\"https\", myhttps);
}
try {
toUse = borrowObject();
while (index <= method.getRetry()) {
try {
m = method.randomMethod();
toUse.executeMethod(m);
T rel = callback.handleResponse(m.getResponseBodyAsString());
return rel;
} catch (Exception e) {
logger.error(\"failed to execute http request.\", e);
index++;
} finally {
try {
m.releaseConnection();
} catch (Exception e) {
// in case fail, ignore and return object
}
}
}
} catch (Exception e) {
return null;
} finally {
if (toUse != null) {
try {
returnObject(toUse);
} catch (Exception e) {
}
}
if (method.isHttps()) {
try {
Protocol.unregisterProtocol(\"https\");
} catch (Exception e) {
}
}
}
// all retry failed
return null;
}
public int getHttpsPort() {
return httpsPort;
}
public void setHttpsPort(int httpsPort) {
this.httpsPort = httpsPort;
}
}

ITPub博客

HttpMethod自定义失败重连