遠程接口調用方式HttpClient
問題：現在我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
什么是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，並且它支持 HTTP 協議最新的版本和建議。實現了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
下載地址：
http://hc.apache.org/
httpclient作用
在java代碼中，發送Http請求。通常用來實現遠程接口調用。
HttpClient測試
在工程中添加httpclient的pom依賴。
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<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
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執行GET請求
public static void doGet(){
// 創建Httpclient對象
CloseableHttpClient httpclient = HttpClients.createDefault();
// 創建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());
// 判斷返回狀態是否為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(){
// 創建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);
// 創建http GET請求
HttpGet httpGet = new HttpGet(uri);
// 執行請求
response = httpclient.execute(httpGet);
// 判斷返回狀態是否為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(){
// 創建Httpclient對象
CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
// 創建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());
// 判斷返回狀態是否為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{
// 創建Httpclient對象
CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
// 創建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());
// 判斷返回狀態是否為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
原因：網站設置了反爬蟲機制，禁止非法訪問。
解決方案：偽裝瀏覽器。
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，用於創建客戶端對象。
* 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，用於創建客戶端對象。
* 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需要指定重定向的策略，如果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
* 原因：
* 有些網站，設置了反爬蟲機制
* 解決的辦法：
* 設置請求頭，偽裝瀏覽器
*/
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);
}
}