HttpClient發起post、get請求

參考文章:

http://blog.csdn.net/wangpeng047/article/details/19624529

http://blog.csdn.net/zknxx/article/details/51598852

一、所需jar包

HttpClient 是apache 組織下面的一個用於處理HTTP 請求和響應的開源工具。所需jar包:

commons-logging-1.1.1.jar、httpclient-4.5.2.jar、httpcore-4.4.4.jar

二、使用方法

使用HttpClient發送請求、接收響應很簡單,一般需要如下幾步即可。

1. 創建HttpClient對象。

2. 創建請求方法的實例,並指定請求URL。如果需要發送GET請求,創建HttpGet對象;如果需要發送POST請求,創建HttpPost對象。

3. 如果需要發送請求參數,可調用HttpGet、HttpPost共同的setParams(HetpParams params)【過時,不推薦使用】方法來添加請求參數;對於HttpPost對象而言,也可調用setEntity(HttpEntity entity)方法來設置請求參數。對於HttpGet對象,可通過拼接url來添加請求參數。

4. 調用HttpClient對象的execute(HttpUriRequest request)發送請求,該方法返回一個HttpResponse。

5. 調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭;

調用HttpResponse的getEntity()方法可獲取HttpEntity對象,該對象包裝了服務器的響應內容。程序可通過該對象獲取服務器的響應內容。

6. 釋放連接。無論執行方法是否成功,都必須釋放連接

三、示例

package com.learn.http;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
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.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

public class HttpSend {

	public static void main(String[] args) {
		// post請求百度地址,返回404
		new HttpSend().post("http://www.baidu.com");
		new HttpSend().get("http://www.baidu.com");
	}

	/**
	 * 發送 post請求訪問本地應用並根據傳遞參數不同返回不同結果
	 */
	public void post(String url) {

		// 創建默認的httpClient實例.
		CloseableHttpClient httpclient = HttpClients.createDefault();
		// 創建httppost
		HttpPost httppost = new HttpPost(url);
		
		// 創建參數隊列
		List<NameValuePair> formparams = new ArrayList<NameValuePair>();
		// 添加參數
		// formparams.add(new BasicNameValuePair("gg", "1"));

		UrlEncodedFormEntity uefEntity;
		try {
			//傳入空參數,創建實體對象
			uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
			//設置post對象的實體對象
			httppost.setEntity(uefEntity);
			System.out.println("executing post request " + httppost.getURI());
			//執行post請求
			CloseableHttpResponse response = httpclient.execute(httppost);
			try {
				//獲取請求結果對象
				HttpEntity entity = response.getEntity();
				if (entity != null) {
					System.out.println("--------------------------------------");
					System.out.println("Response content: " + EntityUtils.toString(entity));
					System.out.println("--------------------------------------");
				}
			} finally {
				response.close();
			}
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e1) {
			e1.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			// 關閉連接,釋放資源
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 發送 get請求
	 */
	public void get(String url) {

		// 創建默認的httpClient實例.
		CloseableHttpClient httpclient = HttpClients.createDefault();
		
		try {
			// 封裝請求參數
			List<NameValuePair> params = new ArrayList<>();
			params.add(new BasicNameValuePair("cityEname", "henan"));
			//轉換爲鍵值對
			String str = EntityUtils.toString(new UrlEncodedFormEntity(params, "UTF-8"));
			System.out.println(str);
			//創建帶參數get請求(示例)
			HttpGet httpGet = new HttpGet(url+"?"+str);

			// 創建不帶參數get請求
			HttpGet httpget = new HttpGet(url);
			System.out.println("executing get request " + httpget.getURI());
			// 執行get請求.
			CloseableHttpResponse response = httpclient.execute(httpget);
			try {
				// 獲取響應實體
				HttpEntity entity = response.getEntity();
				System.out.println("--------------------------------------");
				// 打印響應狀態
				System.out.println(response.getStatusLine());
				if (entity != null) {
					// 打印響應內容長度
					System.out.println("Response content length: " + entity.getContentLength());
					// 打印響應內容
					System.out.println("Response content: " + EntityUtils.toString(entity));
				}
				System.out.println("------------------------------------");
			} finally {
				response.close();
			}
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (ParseException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			// 關閉連接,釋放資源
			try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}



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