1.在安卓端选择从相册还是相机中获取图片
2.用data获取图片，再用crop裁剪图片,并设置头像
3.将Bitmap格式转换为String格式
4.用okhttp post/get的方式向服务器发送String（如果直接用后缀的方式，一般情况下会报错，因为服务器的请求设置了大小限制，在tomacat的话，在server.xml中配置最大限制就可以了）
5.服务端接收到String，并将其保存到数据库

	//全局静态变量
	private static final int PHOTO_REQUEST_CAREMA = 1;// 拍照
    private static final int PHOTO_REQUEST_GALLERY = 2;// 从相册中选择
    private static final int PHOTO_REQUEST_CUT = 3;// 结果

	  // 激活系统图库，选择一张图片
                Intent intent1 = new Intent(Intent.ACTION_PICK);
                intent1.setType("image/*");
                // 开启一个带有返回值的Activity，请求码为PHOTO_REQUEST_GALLERY
                startActivityForResult(intent1, PHOTO_REQUEST_GALLERY);	

 	//激活照相机，省略

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == PHOTO_REQUEST_GALLERY) {
            // 从相册返回的数据
            if (data != null) {
                // 得到图片的全路径
                Uri uri = data.getData();
                crop(uri);
            }
        } else if (requestCode == PHOTO_REQUEST_CUT) {
            // 从剪切图片返回的数据
            if (data != null) {
                Bitmap bitmap = data.getParcelableExtra("data");
                /**
                 * 获得图片
                 */
                imageView1.setImageBitmap(bitmap);
                //转化格式
                String imgString=changeToString(bitmap);
                
                String address="androidtest?imgstring="+imgString;
                
                //上传服务器
                serverPostPicture(address);
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }




 private void crop(Uri uri) {
        // 裁剪图片意图
        Intent intent = new Intent("com.android.camera.action.CROP");
        intent.setDataAndType(uri, "image/*");
        intent.putExtra("crop", "true");
        // 裁剪框的比例，1：1
        intent.putExtra("aspectX", 1);
        intent.putExtra("aspectY", 1);
        // 裁剪后输出图片的尺寸大小
        intent.putExtra("outputX", 250);
        intent.putExtra("outputY", 250);

        intent.putExtra("outputFormat", "JPEG");// 图片格式
        intent.putExtra("noFaceDetection", true);// 取消人脸识别
        intent.putExtra("return-data", true);
        // 开启一个带有返回值的Activity，请求码为PHOTO_REQUEST_CUT
        startActivityForResult(intent, PHOTO_REQUEST_CUT);
    }

	private String changeToString(Bitmap bitmap){

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 80, byteArrayOutputStream);
        //第二步:利用Base64将字节数组输出流中的数据转换成字符串String
        byte[] byteArray = byteArrayOutputStream.toByteArray();
        String imageString = new String(Base64.encodeToString(byteArray, Base64.DEFAULT));
        if(imageString!=null){
            return imageString;
        }
        else {
            return "";
        }

    }

private void serverGetPicture(String address){
            HttpUtil.sendOkHttpRequest(address, new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            textView2.setText("失败");
                        }
                    });
                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    final String responsedata=response.body().string();
                    if(response!=null){
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                changeToBitmap(responsedata);
                            }
                        });
                    }
                }
            });
    }

public class HttpUtil {
    //final static String IP="http://192.168.137.1:8080/caidao/"; //手机连电脑热点，查看本地连接
    final static String IP="http://192.168.43.175:8080/caidao/";//电脑连手机热点，查看wlan连接
    public static void sendOkHttpRequest(String address,okhttp3.Callback callback){
        address =IP+address;
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(address).build();
        client.newCall(request).enqueue(callback);
   	 }
    }

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
		String imgstring=request.getParameter("imgstring");//获得字符串
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html");
		
		System.out.println(“text”);//服务端输出text

		//上传数据库代码省略

		  PrintWriter out = response.getWriter();
		  out.print("上传成功");//利用response返回给android端
		  out.flush();
		  out.close();
		
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}