HttpClient 是apache 組織下面的一個用于處理HTTP 請求和響應的開源工具。所用jar包為httpclient-4.3.6.jar、httpcore-4.3.3.jar、httpmime-4.3.6.jar、commons-codec-1.6.jar。
發送Get請求代碼如下：

package com.zkn.newlearn.httpclient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.List;

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

import com.google.common.collect.Lists;

public class HttpClientTest02 {

    public static void main(String[] args) {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        InputStream is = null;
        String url = "http://localhost:8080/MyWebxTest/getCityByProvinceEname.do";
        //封裝請求參數
        List<NameValuePair> params = Lists.newArrayList();
        params.add(new BasicNameValuePair("cityEname", "henan"));
        String str = "";
        try {
            //轉換為鍵值對
            str = EntityUtils.toString(new UrlEncodedFormEntity(params, Consts.UTF_8));
            System.out.println(str);
            //創建Get請求
            HttpGet httpGet = new HttpGet(url+"?"+str);
            //執行Get請求，
            response = httpClient.execute(httpGet);
            //得到響應體
            HttpEntity entity = response.getEntity();
            if(entity != null){
                is = entity.getContent();
                //轉換為字節輸入流
                BufferedReader br = new BufferedReader(new InputStreamReader(is, Consts.UTF_8));
                String body = null;
                while((body=br.readLine()) != null){
                    System.out.println(body);
                }
            }
        } catch (ParseException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally{
            //關閉輸入流，釋放資源
            if(is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            //消耗實體內容
            if(response != null){
                try {
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            //關閉相應 丟棄http連接
            if(httpClient != null){
                try {
                    httpClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        
    }
}