Java网络请求（get/post）工具类实现的两种方式

1. 基于HttpClient实现

   基本思路都是一样的，通过HttpResponse实例获得请求返回的数据体，具体数据封装在HttpEntity对象中。

/**
 * Created by Song on 2016/11/28.
 * 基于HttpClient提供网络访问工具
 */
public final class NetUtil {
    public static CloseableHttpClient httpClient = HttpClientBuilder.create().build();

    /**
     * get请求获取String类型数据
     * @param url 请求链接
     * @return
     */
    public static String get(String url){
        StringBuffer sb = new StringBuffer();
        HttpGet httpGet = new HttpGet(url);
        try {
            HttpResponse response = httpClient.execute(httpGet);           //1

            HttpEntity entity = response.getEntity();
            InputStreamReader reader = new InputStreamReader(entity.getContent(),"utf-8");
            char [] charbufer;
            while (0new char[10])){
                sb.append(charbufer);
            }
        }catch (IOException e){//1
            e.printStackTrace();
        }finally {
            httpGet.releaseConnection();
        }
        return sb.toString();
    }

    /**
     * post方式请求数据
     * @param url 请求链接
     * @param data post数据体
     * @return
     */
    public static String post(String url, Map data){
        StringBuffer sb = new StringBuffer();
        HttpPost httpPost = new HttpPost(url);
        List valuePairs = new ArrayList();
        if(null != data) {
            for (String key : data.keySet()) {
                valuePairs.add(new BasicNameValuePair(key, data.get(key)));
            }
        }
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(valuePairs));
            HttpResponse response = httpClient.execute(httpPost);
            HttpEntity httpEntity = response.getEntity();
            BufferedInputStream bis = new BufferedInputStream(httpEntity.getContent());
            byte [] buffer;
            while (0new byte[128])){
                sb.append(new String(buffer,"utf-8"));
            }
        }catch (UnsupportedEncodingException e){//数据格式有误
            e.printStackTrace();
        }catch (IOException e){//请求出错
            e.printStackTrace();
        }finally {
            httpPost.releaseConnection();
        }
        return sb.toString();
    }
 }

1. 基于Java net工具包
   基本思路是通过HttpURLConnection 对象设置网络连接参数，建立网络连接，与获得请求返回的网络数据输入流，并从中获得数据。对于JSON格式的数据体，可进一步封装为JSONObject。

import net.sf.json.JSONObject;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * 实现GET以及POST请求
 * mail:[email protected]
 */
public class UrlReqUtil {
    public static JSONObject get(String url){
        HttpURLConnection http = null;
        InputStream is = null;
        try {
            URL urlGet = new URL(url);
            http = (HttpURLConnection) urlGet.openConnection();

            http.setRequestMethod("GET");
            http.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
            http.setDoOutput(true);
            http.setDoInput(true);
            System.setProperty("sun.net.client.defaultConnectTimeout", "30000");
            System.setProperty("sun.net.client.defaultReadTimeout", "30000");

            http.connect();

            is =http.getInputStream();
            int size =is.available();
            byte[] jsonBytes =new byte[size];
            is.read(jsonBytes);
            String message=new String(jsonBytes,"UTF-8");
            return JSONObject.fromObject(message);
        } catch (Exception e) {
            return null;
        }finally {
            if(null != http) http.disconnect();
            try {
                if (null != is) is.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }

    }

    public static String post(String url,String data){
        HttpURLConnection http = null;
        PrintWriter out = null;
        BufferedReader reader = null;
        try {
            //创建连接
            URL urlPost = new URL(url);
            http = (HttpURLConnection) urlPost
                    .openConnection();
            http.setDoOutput(true);
            http.setDoInput(true);
            http.setRequestMethod("POST");
            http.setUseCaches(false);
            http.setInstanceFollowRedirects(true);
            http.setRequestProperty("Content-Type",
                    "application/x-www-form-urlencoded");

            http.connect();

            //POST请求
            OutputStreamWriter outWriter = new OutputStreamWriter(http.getOutputStream(), "utf-8");
            out = new PrintWriter(outWriter);
            out.print(data);
            out.flush();
            out.close();
            out = null;

            //读取响应
            reader = new BufferedReader(new InputStreamReader(
                    http.getInputStream()));
            String lines;
            StringBuffer sb = new StringBuffer("");
            while ((lines = reader.readLine()) != null) {
                lines = new String(lines.getBytes(), "utf-8");
                sb.append(lines);
            }
            reader.close();
            reader = null;
            System.out.println(sb.toString());
            return sb.toString();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }finally {
            if(null != http) http.disconnect();
            if(null != out) out.close();
            try{
                if(null != reader) reader.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }

    }
}