服务器代码没问题。因为web-〉server = image文件可以上传，而Android -〉server= imge文件不能上传，所以Android代码无法将img发送到jsp（Tomcat服务器）。
Android服务器：

package com.example.nfc_s;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity; import android.content.Intent; import
android.database.Cursor; import android.graphics.Bitmap; import
android.net.Uri; import android.os.Bundle; import
android.os.StrictMode; import android.provider.MediaStore; import
android.util.Log; import android.view.View; import
android.widget.Button; import android.widget.ImageView; import
android.widget.Toast;

import java.io.DataOutputStream; import java.io.FileInputStream;
import java.io.InputStream; import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity2 extends AppCompatActivity {
    ImageView imageView = null;
    Button button = null;
    private final int REQ_CODE_SELECT_IMAGE = 100;
    private String img_path = new String();
    private String serverURL = "http://localhost:8080/testDB2/upload.jsp";
    //<<서버주소
    private Bitmap image_bitmap_copy = null;
    private Bitmap image_bitmap = null;
    private String imageName = null;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
                .permitDiskReads()
                .permitDiskWrites()
                .permitNetwork().build());

        imageView = (ImageView) findViewById(R.id.imageView);
        //이미지를 띄울 위젯
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_PICK);
                intent.setType(MediaStore.Images.Media.CONTENT_TYPE);
                intent.setData(MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                startActivityForResult(intent, REQ_CODE_SELECT_IMAGE);
            }
        });

        button = (Button) findViewById(R.id.button);
        //이미지 전송 버튼
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                DoFileUpload(serverURL, img_path);
                Toast.makeText(getApplicationContext(), "이미지 전송 성공", Toast.LENGTH_SHORT).show();
                Log.d("Send", "Success");
            }
        });
    }//end of onCreate()

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        Toast.makeText(getBaseContext(), "resultCode : " + data, Toast.LENGTH_SHORT).show();

        if (requestCode == REQ_CODE_SELECT_IMAGE) {
            if (resultCode == Activity.RESULT_OK) {
                try {
                    img_path = getImagePathToUri(data.getData()); //이미지의 URI를 얻어 경로값으로 반환.
                    Toast.makeText(getBaseContext(), "img_path : " + img_path, Toast.LENGTH_SHORT).show();
                    //이미지를 비트맵형식으로 반환
                    image_bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(),
data.getData());

                    //사용자 단말기의 width , height 값 반환
                    int reWidth = (int) (getWindowManager().getDefaultDisplay().getWidth());
                    int reHeight = (int) (getWindowManager().getDefaultDisplay().getHeight());

//image_bitmap 으로 받아온 이미지의 사이즈를 임의적으로 조절함. width: 400 , height: 300
                    image_bitmap_copy = Bitmap.createScaledBitmap(image_bitmap, 400, 300, true);
                    ImageView image = (ImageView) findViewById(R.id.imageView);  //이미지를 띄울 위젯 ID값
                    image.setImageBitmap(image_bitmap_copy);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }//end of onActivityResult()

    public String getImagePathToUri(Uri data) {
        //사용자가 선택한 이미지의 정보를 받아옴
        String[] proj = {MediaStore.Images.Media.DATA};
        Cursor cursor = managedQuery(data, proj, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();

        //이미지의 경로 값
        String imgPath = cursor.getString(column_index);
        Log.d("test", imgPath);

        //이미지의 이름 값
        String imgName = imgPath.substring(imgPath.lastIndexOf("/") + 1);
        Toast.makeText(MainActivity2.this, "이미지 이름 : " + imgName, Toast.LENGTH_SHORT).show();
        this.imageName = imgName;

        DoFileUpload("http://localhost:8080/testDB2/upload.jsp",imgPath);

        return imgPath;
    }//end of getImagePathToUri()

    public void DoFileUpload(String apiUrl, String absolutePath) {
        HttpFileUpload(apiUrl, "", absolutePath);
    }

    String lineEnd = "\r\n";
    String twoHyphens = "--";
    String boundary = "*****";

    public void HttpFileUpload(String urlString, String params, String fileName) {
        try {

            FileInputStream mFileInputStream = new FileInputStream(fileName);
            URL connectUrl = new URL(urlString);
            Log.d("Test", "mFileInputStream  is " + mFileInputStream);

            // HttpURLConnection 통신
            HttpURLConnection conn = (HttpURLConnection) connectUrl.openConnection();
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Connection", "Keep-Alive");
            conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);

            // write data
            DataOutputStream dos = new DataOutputStream(conn.getOutputStream());
            dos.writeBytes(twoHyphens + boundary + lineEnd);
            dos.writeBytes("Content-Disposition: form-data; name=\"uploadedfile\"; filename=\"" + fileName + "\"" + lineEnd);
            dos.writeBytes(lineEnd);

            int bytesAvailable = mFileInputStream.available();
            int maxBufferSize = 1024;
            int bufferSize = Math.min(bytesAvailable, maxBufferSize);

            byte[] buffer = new byte[bufferSize];
            int bytesRead = mFileInputStream.read(buffer, 0, bufferSize);

            Log.d("Test", "image byte is " + bytesRead);

            // read image
            while (bytesRead > 0) {
                dos.write(buffer, 0, bufferSize);
                bytesAvailable = mFileInputStream.available();
                bufferSize = Math.min(bytesAvailable, maxBufferSize);
                bytesRead = mFileInputStream.read(buffer, 0, bufferSize);
            }

            dos.writeBytes(lineEnd);
            dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

            // close streams
            Log.e("Test", "File is written");
            mFileInputStream.close();
            dos.flush();
            // finish upload...

            // get response
            InputStream is = conn.getInputStream();

            StringBuffer b = new StringBuffer();
            for (int ch = 0; (ch = is.read()) != -1; ) {
                b.append((char) ch);
            }
            is.close();
            Log.e("Test", b.toString());

        } catch (Exception e) {
            Log.d("Test", "exception " + e.getMessage());
            // TODO: handle exception
        }
    } // end of HttpFileUpload() } //end of class