HttpClient入门示例

       如果你是使用maven来管理项目，你需要在pom.xml添加如下配置：

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
            <version>4.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpcore</artifactId>
            <version>4.4.1</version>
        </dependency>

示例代码如下：

package org.apache.http.examples.entity.mime;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.UnknownHostException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.net.ssl.SSLException;

import org.apache.commons.codec.Charsets;
import org.apache.http.Header;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.HttpRequestRetryHandler;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.config.SocketConfig;
import org.apache.http.conn.ConnectTimeoutException;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;

/**
* 使用HttpClient发送和接收Http请求
*
* @author manzhizhen
*
*/
public class HttpUtils {

private static HttpClient httpClient;
// 最大连接数
private static final int MAX_CONNECTION = 100;
// 每个route能使用的最大连接数，一般和MAX_CONNECTION取值一样
private static final int MAX_CONCURRENT_CONNECTIONS = 100;
// 建立连接的超时时间，单位毫秒
private static final int CONNECTION_TIME_OUT = 200;
// 请求超时时间，单位毫秒
private static final int REQUEST_TIME_OUT = 200;
// 最大失败重试次数
private static final int MAX_FAIL_RETRY_COUNT = 3;
// 请求配置，可以复用
private static RequestConfig requestConfig;

static {
SocketConfig socketConfig = SocketConfig.custom()
.setSoTimeout(REQUEST_TIME_OUT).setSoKeepAlive(true)
.setTcpNoDelay(true).build();

requestConfig = RequestConfig.custom()
.setSocketTimeout(REQUEST_TIME_OUT)
.setConnectTimeout(CONNECTION_TIME_OUT).build();
/**
* 每个默认的 ClientConnectionPoolManager 实现将给每个route创建不超过2个并发连接，最多20个连接总数。
*/
PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();
connManager.setMaxTotal(MAX_CONNECTION);
connManager.setDefaultMaxPerRoute(MAX_CONCURRENT_CONNECTIONS);
connManager.setDefaultSocketConfig(socketConfig);

httpClient = HttpClients.custom().setConnectionManager(connManager)
// 添加重试处理器
.setRetryHandler(new MyHttpRequestRetryHandler()).build();
}

public static void main(String[] args) {
testGet();
}

/**
* 测试get方法
*/
private static void testGet() {
String url = "http://restapi.amap.com/v3/place/text";
Map<String, String> paramMap = new HashMap<String, String>();
paramMap.put("key", "95708f902ac2428ea119ec99fb70e6a3");
paramMap.put("keywords", "互联网金融大厦");
paramMap.put("city", "330100");
paramMap.put("extensions", "all");

try {
System.out.println(get(url, paramMap));

} catch (Exception e) {
e.printStackTrace();
}
}

/**
* post请求
*
* @param url
* @param paramMap
* @param headers
* @return
* @throws Exception
*/
public static String post(String url, Map<String, String> paramMap,
List<Header> headers) throws Exception {
URIBuilder uriBuilder = new URIBuilder(url);
if (paramMap != null) {
// 添加请求参数
for (Entry<String, String> entry : paramMap.entrySet()) {
uriBuilder.addParameter(entry.getKey(), entry.getValue());
}
}

HttpPost httpPost = new HttpPost(uriBuilder.build());
if (headers != null) {
// 添加请求首部
for (Header header : headers) {
httpPost.addHeader(header);
}
}

httpPost.setConfig(requestConfig);

// 执行请求
HttpResponse response = httpClient.execute(httpPost);

return EntityUtils.toString(response.getEntity(), Charsets.UTF_8);
}

/**
* post请求，不带请求首部
*
* @param url
* @param paramMap
* @return
* @throws Exception
*/
public static String post(String url, Map<String, String> paramMap)
throws Exception {

return post(url, paramMap, null);
}

/**
* get请求
*
* @param url
* @param paramMap
* @param headers
* @return
* @throws Exception
*/
public static String get(String url, Map<String, String> paramMap,
List<Header> headers) throws Exception {
URIBuilder uriBuilder = new URIBuilder(url);
if (paramMap != null) {
// 添加请求参数
for (Entry<String, String> entry : paramMap.entrySet()) {
uriBuilder.addParameter(entry.getKey(), entry.getValue());
}
}

HttpGet httpGet = new HttpGet(uriBuilder.build());
if (headers != null) {
// 添加请求首部
for (Header header : headers) {
httpGet.addHeader(header);
}
}

httpGet.setConfig(requestConfig);

// 执行请求
HttpResponse response = httpClient.execute(httpGet);

return EntityUtils.toString(response.getEntity(), Charsets.UTF_8);
}

/**
* get请求，不带请求首部
*
* @param url
* @param paramMap
* @return
* @throws Exception
*/
public static String get(String url, Map<String, String> paramMap)
throws Exception {

return get(url, paramMap, null);
}

/**
* 请求重试处理器
* @author manzhizhen
*
*/
private static class MyHttpRequestRetryHandler implements
HttpRequestRetryHandler {

@Override
public boolean retryRequest(IOException exception, int executionCount,
HttpContext context) {
if (executionCount >= MAX_FAIL_RETRY_COUNT) {
return false;
}

if (exception instanceof InterruptedIOException) {
// 超时
return false;
}
if (exception instanceof UnknownHostException) {
// 未知主机
return false;
}
if (exception instanceof ConnectTimeoutException) {
// 连接被拒绝
return false;
}
if (exception instanceof SSLException) {
// SSL handshake exception
return false;
}

HttpClientContext clientContext = HttpClientContext.adapt(context);
HttpRequest request = clientContext.getRequest();
boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
if (idempotent) {
// 如果请求被认为是幂等的，则重试
return true;
}

return false;
}
}
}