HttpClient 遠程接口調用方式

遠程接口調用方式HttpClient

問題：如今咱們已經開發好了接口了，那該如何調用這個接口呢？

答：使用Httpclient客戶端。

 

Httpclient簡介

什麼是httpclient

HttpClient 是 Apache Jakarta Common 下的子項目，用來提供高效的、最新的、功能豐富的支持 HTTP 協議的客戶端編程工具包，而且它支持 HTTP 協議最新的版本和建議。實現了全部 HTTP 的方法（GET,POST,PUT,HEAD 等）

下載地址：http://hc.apache.org/

 

httpclient做用

在java代碼中，發送Http請求。一般用來實現遠程接口調用。

HttpClient測試

在工程中添加httpclient的pom依賴。

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
</dependency>

 

執行GET請求

public static void doGet(){ // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClients.createDefault(); // 建立http GET請求
        HttpGet httpGet = new HttpGet("http://www.oschina.net/"); CloseableHttpResponse response = null; try { // 執行請求
            response = httpclient.execute(httpGet); System.out.println(response.getStatusLine()); // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println("內容長度：" + content.length()); } }catch(Exception e){ e.printStackTrace(); } finally { if (response != null) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { e.printStackTrace(); } }

 

 

執行GET帶參數

public static void doGetParam(){ // 建立Httpclient對象
CloseableHttpClient httpclient = HttpClients.createDefault(); CloseableHttpResponse response = null; try { // 定義請求的參數
        URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "數據庫").build(); System.out.println(uri); // 建立http GET請求
        HttpGet httpGet = new HttpGet(uri); // 執行請求
            response = httpclient.execute(httpGet); // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } }catch(Exception e){ e.printStackTrace(); }finally { if (response != null) { try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block
e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block
e.printStackTrace(); } } }

 

執行post請求

public static void doPost(){ // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build(); // 建立http POST請求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/"); CloseableHttpResponse response = null; try { // 執行請求
            response = httpclient.execute(httpPost); System.out.println(response.getStatusLine()); // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } }catch(Exception e){ e.printStackTrace(); }finally { if (response != null) { try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block
e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block
e.printStackTrace(); } } }

 

 

執行post帶參數

public static void doPostParam() throws Exception{ // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build(); // 建立http POST請求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/search"); // 設置2個post參數，一個是scope、一個是q
        List<NameValuePair> parameters = new ArrayList<NameValuePair>(); parameters.add(new BasicNameValuePair("scope", "project")); parameters.add(new BasicNameValuePair("q", "java")); // 構造一個form表單式的實體
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters); // 將請求實體設置到httpPost對象中
 httpPost.setEntity(formEntity); CloseableHttpResponse response = null; try { // 執行請求
            response = httpclient.execute(httpPost); System.out.println(response.getStatusLine()); // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } } finally { if (response != null) { response.close(); } httpclient.close(); } }

 

 

httpclient常見問題及解決方案

請求參數亂碼

設置請求的編碼格式：

obj.addHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF-8"); 

 

 

 

響應HTTP/1.1 403 Forbidden

緣由：網站設置了反爬蟲機制，禁止非法訪問。

解決方案：假裝瀏覽器。

obj.addHeader("User-Agent"," Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537. 36 (KHTML, like Gecko) Chrome/31.0.1650.63") 

 

 

封裝通用工具類HttpClientUtils

package org.chu.ego.base.utils; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Map; import org.apache.http.HttpEntity; import org.apache.http.NameValuePair; 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.client.utils.URIBuilder; 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.impl.client.LaxRedirectStrategy; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; /** * --發送get請求的api * CloseableHttpClient類 ，client實現類 * HttpClients類 ，client工具類，用於建立客戶端對象。 * CloseableHttpResponse接口，請求的響應對象 * URIBuilder類 ：url構建類，用於設置get請求的路徑變量 * HttpGet類 ：get請求的發送對象 * EntityUtils類 實體處理類 * * --發送post 請求使用的api * CloseableHttpClient類 * HttpClientBuilder client構建對象，用於建立客戶端對象。 * LaxRedirectStrategy類，post請求重定向的策略 * CloseableHttpResponse 請求的響應對象 * HttpPost post請求的發送對象 * NameValuePair 類，用於設置參數值 * UrlEncodedFormEntity：用於設置表單參數給發送對象HttpPost * * @author ranger * */
public class HttpClientUtils { public static String doGet(String url,Map<String, String> params){ //獲取httpclient客戶端
        CloseableHttpClient httpclient = HttpClients.createDefault(); String resultString = ""; CloseableHttpResponse response = null; try { URIBuilder builder = new URIBuilder(url); if(null!=params){ for (String key:params.keySet()) { builder.setParameter(key, params.get(key)); } } HttpGet get = new HttpGet(builder.build()); response = httpclient.execute(get); System.out.println(response.getStatusLine()); if(200==response.getStatusLine().getStatusCode()){ HttpEntity entity = response.getEntity(); resultString = EntityUtils.toString(entity, "utf-8"); } } catch (Exception e) { e.printStackTrace(); } finally { if(null!=response){ try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block
 e.printStackTrace(); } } if(null!=httpclient){ try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block
 e.printStackTrace(); } } } return resultString; } public static String doGet(String url){ return doGet(url, null); } public static String doPost(String url,Map<String,String> params){ /** * 在4.0及以上httpclient版本中，post須要指定重定向的策略，若是不指定則按默認的重定向策略。 * * 獲取httpclient客戶端 */ CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy( new LaxRedirectStrategy()).build(); String resultString = ""; CloseableHttpResponse response = null; try { HttpPost post = new HttpPost(url); List<NameValuePair> paramaters = new ArrayList<>(); if(null!=params){ for (String key : params.keySet()) { paramaters.add(new BasicNameValuePair(key,params.get(key))); } UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity (paramaters); post.setEntity(formEntity); } /** * HTTP/1.1 403 Forbidden * 緣由： * 有些網站，設置了反爬蟲機制 * 解決的辦法： * 設置請求頭，假裝瀏覽器 */ post.addHeader("user-agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"); response = httpclient.execute(post); System.out.println(response.getStatusLine()); if(200==response.getStatusLine().getStatusCode()){ HttpEntity entity = response.getEntity(); resultString = EntityUtils.toString(entity, "utf-8"); } } catch (Exception e) { e.printStackTrace(); } finally { if(null!=response){ try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block
 e.printStackTrace(); } } if(null!=httpclient){ try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block
 e.printStackTrace(); } } } return resultString; } public static String doPost(String url){ return doPost(url, null); } }