http请求get与post请求的几种实现

/**
*    普通表单调用
*    根据参数url，处理post请求，获取远程返回的response，然后返回相对应的ActionResult
*
*/
public ActionResult post(String url, Map<String,String> params){
    /**
    1.创建httpClient对象
    2.创建HttpPost对象
    3.设置post请求的实体内容
    4.通过HttpPost对象执行post请求，获得response
    5.获得response的实体内容(json格式)，将实体内容转换成字符串(实际上是json格式的字符串)，最后将json字符串转换成ActionResult对象
    */
    DefaultHttpClient httpClient = new DefaultHttpClient();
    
    HttpPost post = new HttpPost(url);
    
    List<NameValuePair> nvps = new ArrayList<NameValuePair>();
    
    for(Map.Entry<String,String> entry : params.entrySet()){
        
        nvps.add(new BasicNameValuePair(entry.getKey(),entry.getValue()));
        
    }
    try{
        
        post.setEntity(new UrlEncodedFormEntity(nvps,charsetName));
        
        HttpResponse response = httpClient.execute(post);
        
        HttpEntity entity = response.getEntity();
        
        return JsonUtils.fromString(EntityUtils.toString(entity,"utf-8"),ActionResult.class);
        
        
    }catch(Exception e){
        
        e.printStackTrace();
        
        return null;
        
    }finally{
        try{
            
            httpClient.getConnetionManager.shutdown();
            
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

/**
*带文件上传的表单
*
*/
public ActionResult postWithFile(String url, Map<String,Object> params){

    DefaultHttpClient httpClient = new DefaultHttpClient();

    HttpPost post = new HttpPost(url);

    MultipartEntity reqEntity = new MultipartEntity();

    try{
        for(Map.Entry<String, Object> entry : params.entrySet()){

            String key = entry.getKey();

            Object value = entry.getValue();

            if(value instanceof File){

                File file = (File)value;

                FileBody fileBody = new FileBody(file);

                reqEntity.addPart(key,fileBody);

            }else{

                StringBody stringBody = new StringBody(String.valueOf(value),Charset.forName("utf-8"));

                reqEntity.addPart(key, stringBody);
            }
        }

        post.setEntity(reqEntity);

        HttpResponse response = httpClient.execute(post);

        HttpEntity entity = response.getEntity();

        return JsonUtils.fromString(EntityUtils.toString(entity,"utf-8"),
                            ActionResult.class);

    }catch(Exception e){

        e.printStackTrace();

        return null;

    }finally{

        try{

            httpClient.getConnetionManager.shutdown();

        }catch(Exception e){

            e.printStackTrace();
        }
    }
}

/**
*不依赖第三发jar包实现，处理get请求以及普通post请求的方法
*
*/
public String getOrPost(String type, String url, String encoding, String contentType, String params, HttpServletRequest request){
    /**
    *    1.确定编码和contentType
        2.确定url：如果传入url不包含http，则应当重新组装url
        3.确定请求参数(GET请求)
        4.创建URLConnection对象
        5.设置URLConnection对象的属性(请求方式/是否使用缓存/本次连接是否自动处理重定向/UA/Accept/)
                如果是post请求，则必须设置DoInput,DoOutput,Content-Type
                post请求不能使用缓存（设置http请求头属性）
        6.创建真实连接
        7.如果是post请求，则设置http请求正文
        8.获取远程返回的InputStream，读取InputStream,返回结果
        9.关闭流，断开连接
    *
    */
    encoding = encoding==null ? "utf-8" : encoding;
    
    contentType = contentType==null ? "application/x-www-form-urlencoded" : contentType;
    
    if(!url.startsWith("http://") && !url.startsWith("https://") && request!=null){
        url = getBasePath(request)+url;
    }
    
    if("GET".equals(type) && notEmtpy(params)){
        if(!url.contains("?")){
            url+="?"+params;
        }else{
            url+="&"+params;
        }
    }
    
    HttpURLConnection conn = (HttpURLConnection)new URL(url).openConnection();
    
    //设置请求头
    conn.setRequestMethod(type);
    conn.setUseCaches(false);
    conn.setInstanceFollowRedirects(true);
    conn.setRequestProperty("user-agent",
                "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31");
    conn.setRequestProperty("accept","*/*");
    
    if("POST".equals(type)){
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setRequestProperty("Content-Type",contentType);
    }
    
    //实际上只是建立了一个与服务器的TCP连接，并没有发送http请求；
    //只有在执行conn.getInputStream()时，才真正发送http请求
    conn.connect();
    
    //设置请求正文(POST请求)
    if("POST".equals(type)){
        OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream(),encoding);
        out.write(params);
        out.flush();
        out.close();
    }
    
    //获取数据
    BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(),Charset.forName(encoding)));
    String str;
    StringBuffer sb = new StringBuffer("");
    while((str = br.readLine())!= null){
        sb.append(str);
    }
    br.close();
    conn.disconnect();
    return sb.toString();
    
}