温故HttpClient小记（先拆解，再封装）

官方文档地址：http://hc.apache.org/httpcomponents-client-4.5.x/quickstart.html

一、创建httpClient

1、请求中需要管理cookies，所以使用的不是createDefault()，而是costom()

public static BasicCookieStore cookieStore = new BasicCookieStore();
CloseableHttpClient httpClient = HttpClients.custom()
          .setDefaultCookieStore(cookieStore).build();

二、创建httpGet或HttpPost对象

1、GET方法：

HttpGet get = null;
if (param == null) {
    get = new HttpGet(url);
}else {
    get = new HttpGet(url + "?" + param);

2、POST方法：

HttpPost post = new HttpPost(url);

三、设置Header和超时时间，以及post的请求实体

1、Header设置(若post请求，则使用HttpPost对象调用setHeader()方法即可)

HttpGet get = new HttpGet(url);
get.setHeader("Accept-Encoding", "gzip, deflate, br");
get.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.81 Safari/537.36");

2、超时设置（使用setConfig()方法，需要在方法中传RequestConfig类型参数）

RequestConfig config = RequestConfig.custom().setConnectionRequestTimeout(3000).build();
get.setConfig(config);

3、post请求实体（这里post中的参数param是String类型，form为“a=1&b=2”这种转换好的，若一个一个放则需要用StringEntity的子类UrlEncodedFormEntity）

StringEntity stringEntity = new StringEntity(param);
//JSONUtil是自己封装的关于json的类，isJSON(param)方法判断是否可解析成jsonObject格式
if (JSONUtil.isJSON(param)) {
    stringEntity.setContentType("application/json");
}else {
    stringEntity.setContentType("application/x-www-form-urlencoded");
}
post.setEntity(stringEntity);

注：content-type为form类型的一个一个添加参数方式：

List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("username", "vip"));
nvps.add(new BasicNameValuePair("password", "secret"));
post.setEntity(new UrlEncodedFormEntity(nvps));

四、用httpClient执行httpGet/httpPost得到response

(若post请求，则在execute方法中传入HttpPost对象）

CloseableHttpResponse httpResponse = httpClient.execute(get);

五、从response中获取responseEntity

HttpEntity entity = httpResponse.getEntity();
String actResult = EntityUtils.toString(entity);

六、封装

(HttpGet和HttpPost是HttpRequestBase的子类，HttpRequestBase是HTTPMessage的子类，HttpRequestBase中有setConfig()方法，HTTPMessage有setHeader()方法)

package com.api.util;
import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpUtil {
    
    // 管理cookie的对象
    public static BasicCookieStore cookieStore = new BasicCookieStore();
    
    /**
     * 设置请求头和超时
     * @param httpRequestBase
     * void
     *
     */
    public static void httpConfig(HttpRequestBase httpRequestBase){
        httpRequestBase.setHeader("Accept-Encoding", "gzip, deflate, br");
        httpRequestBase.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.81 Safari/537.36");
        
        RequestConfig config = RequestConfig.custom().setConnectionRequestTimeout(3000).build();
        httpRequestBase.setConfig(config);
    }
    
    /**
     * GET方法
     * @param url
     * @param param
     * @return
     * String
     *
     */
    public static String sendGet(String url,String param){
        CloseableHttpClient httpClient = HttpClients.custom().setDefaultCookieStore(cookieStore).build();
//      CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpGet get = null;
        CloseableHttpResponse httpResponse = null;
        String actResult = null;
        try {
            if (param == null) {
                get = new HttpGet(url);
            }else {
                get = new HttpGet(url + "?" + param);
            }
            httpConfig(get);
            httpResponse = httpClient.execute(get);
            HttpEntity entity = httpResponse.getEntity();
            actResult = EntityUtils.toString(entity);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                httpResponse.close();
                httpClient.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return actResult;
    }
    
    /**
     * POST方法
     * @param url
     * @param param
     * @return
     * String
     *
     */
    public static String sendPost(String url,String param){
        String actResult = null;
        CloseableHttpClient httpClient = HttpClients.custom().setDefaultCookieStore(cookieStore).build();
//      CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost post = new HttpPost(url);
        CloseableHttpResponse httpResponse = null;
        try {
            httpConfig(post);
            StringEntity stringEntity = new StringEntity(param);
            if (JSONUtil.isJSON(param)) {
                stringEntity.setContentType("application/json");
            }else {
                stringEntity.setContentType("application/x-www-form-urlencoded");
            }
            post.setEntity(stringEntity);
            
            httpResponse = httpClient.execute(post);
            HttpEntity entity = httpResponse.getEntity();
            actResult = EntityUtils.toString(entity);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                httpResponse.close();
                httpClient.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return actResult;
    }
}