前言

在日常開發中，我們經常需要通過http協議去呼叫網路內容，雖然java自身提供了net相關工具包，但是其靈活性和功能總是不如人意，於是有人專門搞出一個httpclient類庫，來方便進行Http操作。對於httpcore的原始碼研究，我們可能並沒有達到這種層次，在日常開發中也只是需要的時候，在網上百度一下，然後進行呼叫就行。在專案中對於這個工具類庫也許沒有進行很好的封裝。在哪裡使用就寫在哪些，很多地方用到，就在多個地方寫。反正是複製貼上，很方便，但是這樣就會導致專案中程式碼冗餘。所以這裡簡單的對httpcient的簡單操作封裝成一個工具類，統一放在專案的工具包中，在使用的時候直接從工具包中呼叫，不需要寫冗餘程式碼。

httpclient操作例項

首先需要在注意的一點是，這是基於httpclient4.5版本的，我們在使用的時候需要引入具體對應jar。下面是具體程式碼示例

import java.io.IOException;
import java.security.KeyManagementException;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import
 
 java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.net.ssl.SSLContext;

import org.apache.commons.lang3.StringUtils;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.config.RequestConfig;
import
 
 org.apache.http.client.entity.UrlEncodedFormEntity;
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.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.ssl.SSLContextBuilder;
import org.apache.http.ssl.TrustStrategy;
import org.apache.http.util.EntityUtils;

/**
 * 基於 httpclient 4.5版本的 http工具類
 * 
 * @author 愛琴孩
 * 
 */
public class HttpClientTool {

    private static final CloseableHttpClient httpClient;
    public static final String CHARSET = "UTF-8";
    // 採用靜態程式碼塊，初始化超時時間配置，再根據配置生成預設httpClient物件
    static {
        RequestConfig config = RequestConfig.custom().setConnectTimeout(60000).setSocketTimeout(15000).build();
        httpClient = HttpClientBuilder.create().setDefaultRequestConfig(config).build();
    }

    public static String doGet(String url, Map<String, String> params) {
        return doGet(url, params, CHARSET);
    }

    public static String doGetSSL(String url, Map<String, String> params) {
        return doGetSSL(url, params, CHARSET);
    }

    public static String doPost(String url, Map<String, String> params) throws IOException {
        return doPost(url, params, CHARSET);
    }

    /**
     * HTTP Get 獲取內容
     * @param url 請求的url地址 ?之前的地址
     * @param params 請求的引數
     * @param charset 編碼格式
     * @return 頁面內容
     */
    public static String doGet(String url, Map<String, String> params, String charset) {
        if (StringUtils.isBlank(url)) {
            return null;
        }
        try {
            if (params != null && !params.isEmpty()) {
                List<NameValuePair> pairs = new ArrayList<NameValuePair>(params.size());
                for (Map.Entry<String, String> entry : params.entrySet()) {
                    String value = entry.getValue();
                    if (value != null) {
                        pairs.add(new BasicNameValuePair(entry.getKey(), value));
                    }
                }
                // 將請求引數和url進行拼接
                url += "?" + EntityUtils.toString(new UrlEncodedFormEntity(pairs, charset));
            }
            HttpGet httpGet = new HttpGet(url);
            CloseableHttpResponse response = httpClient.execute(httpGet);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode != 200) {
                httpGet.abort();
                throw new RuntimeException("HttpClient,error status code :" + statusCode);
            }
            HttpEntity entity = response.getEntity();
            String result = null;
            if (entity != null) {
                result = EntityUtils.toString(entity, "utf-8");
            }
            EntityUtils.consume(entity);
            response.close();
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * HTTP Post 獲取內容
     * @param url 請求的url地址 ?之前的地址
     * @param params 請求的引數
     * @param charset 編碼格式
     * @return 頁面內容
     * @throws IOException
     */
    public static String doPost(String url, Map<String, String> params, String charset) 
            throws IOException {
        if (StringUtils.isBlank(url)) {
            return null;
        }
        List<NameValuePair> pairs = null;
        if (params != null && !params.isEmpty()) {
            pairs = new ArrayList<NameValuePair>(params.size());
            for (Map.Entry<String, String> entry : params.entrySet()) {
                String value = entry.getValue();
                if (value != null) {
                    pairs.add(new BasicNameValuePair(entry.getKey(), value));
                }
            }
        }
        HttpPost httpPost = new HttpPost(url);
        if (pairs != null && pairs.size() > 0) {
            httpPost.setEntity(new UrlEncodedFormEntity(pairs, CHARSET));
        }
        CloseableHttpResponse response = null;
        try {
            response = httpClient.execute(httpPost);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode != 200) {
                httpPost.abort();
                throw new RuntimeException("HttpClient,error status code :" + statusCode);
            }
            HttpEntity entity = response.getEntity();
            String result = null;
            if (entity != null) {
                result = EntityUtils.toString(entity, "utf-8");
            }
            EntityUtils.consume(entity);
            return result;
        } catch (ParseException e) {
            e.printStackTrace();
        } finally {
            if (response != null)
                response.close();
        }
        return null;
    }

    /**
     * HTTPS Get 獲取內容
     * @param url 請求的url地址 ?之前的地址
     * @param params 請求的引數
     * @param charset  編碼格式
     * @return 頁面內容
     */
    public static String doGetSSL(String url, Map<String, String> params, String charset) {
        if (StringUtils.isBlank(url)) {
            return null;
        }
        try {
            if (params != null && !params.isEmpty()) {
                List<NameValuePair> pairs = new ArrayList<NameValuePair>(params.size());
                for (Map.Entry<String, String> entry : params.entrySet()) {
                    String value = entry.getValue();
                    if (value != null) {
                        pairs.add(new BasicNameValuePair(entry.getKey(), value));
                    }
                }
                url += "?" + EntityUtils.toString(new UrlEncodedFormEntity(pairs, charset));
            }
            HttpGet httpGet = new HttpGet(url);

            // https  注意這裡獲取https內容，使用了忽略證書的方式，當然還有其他的方式來獲取https內容
            CloseableHttpClient httpsClient = HttpClientTool.createSSLClientDefault();
            CloseableHttpResponse response = httpsClient.execute(httpGet);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode != 200) {
                httpGet.abort();
                throw new RuntimeException("HttpClient,error status code :" + statusCode);
            }
            HttpEntity entity = response.getEntity();
            String result = null;
            if (entity != null) {
                result = EntityUtils.toString(entity, "utf-8");
            }
            EntityUtils.consume(entity);
            response.close();
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 這裡建立了忽略整數驗證的CloseableHttpClient物件
     * @return
     */
    public static CloseableHttpClient createSSLClientDefault() {
        try {
            SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, new TrustStrategy() {
                // 信任所有
                public boolean isTrusted(X509Certificate[] chain, String authType) throws CertificateException {
                    return true;
                }
            }).build();
            SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext);
            return HttpClients.custom().setSSLSocketFactory(sslsf).build();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyStoreException e) {
            e.printStackTrace();
        }
        return HttpClients.createDefault();
    }
}

總結

上面就是對於httpclient的簡單工具類，對於httpclient，還有很多知識點需要仔細研究，後面再和大家一起來總結學習！