在 Android 中使用 JDBC 优化 mysql DB 执行

Question

I have some code in android which is running a query to the database which i have hosted online. I have used AsyncTask to perform DB operation in this activity, similarly I have other activities too which are having similar code and connection procedure. I wanted to know if this is the optimal way to connect to mysql db using JDBC connection in android or can this be improved

The code is taking around 3 sec for login as in MainActivity class.

public class MainActivity extends AppCompatActivity {

private ProgressDialog mProgress;
final int REQUEST_PERMISSION_CODE = 1000;

private static final String url = "jdbc:mysql://192.168.0.103/pos";
private static final String user = "root";
private static final String pass = "";
private EditText mPassword, mUsername;
private Button loginBtn;
private ProgressBar mLoginProgress;
private TextView mLoginFeedbackText;
String password, username;
ProgressDialog progressDialog;
Boolean CheckEditText;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    if (!checkPermissionFromDevice())
        requestPermission();

    mPassword = findViewById(R.id.password);
    mUsername = findViewById(R.id.username);
    loginBtn = findViewById(R.id.generate_btn);
    mLoginProgress = findViewById(R.id.login_progress_bar);
    mLoginFeedbackText = findViewById(R.id.login_form_feedback);
    mProgress = new ProgressDialog(this);
    
    loginBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            CheckEditTextIsEmptyOrNot();
            if (CheckEditText) {
                UserLoginFunction(username, password);
            } else {
                Toast.makeText(MainActivity.this, "Please fill all form fields.", Toast.LENGTH_LONG).show();
            }
        }
    });
}

public void CheckEditTextIsEmptyOrNot() {
    username = mUsername.getText().toString();
    password = mPassword.getText().toString();
    if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {
        CheckEditText = false;
    } else {
        CheckEditText = true;
    }
}

private void requestPermission() {
    ActivityCompat.requestPermissions(this, new String[]{
            Manifest.permission.WRITE_EXTERNAL_STORAGE,
            Manifest.permission.RECORD_AUDIO
    }, REQUEST_PERMISSION_CODE);
}

private boolean checkPermissionFromDevice() {
    int write_external_storage_result = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
    int record_audio_result = ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO);
    return write_external_storage_result == PackageManager.PERMISSION_GRANTED &&
            record_audio_result == PackageManager.PERMISSION_GRANTED;
}
public void UserLoginFunction(final String username, final String password) {
    class UserLoginClass extends AsyncTask<String, Void, String> {
        @Override
        protected void onPreExecute() {
            System.out.println("In onPreExecute");
            super.onPreExecute();

            progressDialog = ProgressDialog.show(MainActivity.this, "Loading Data", null, true, true);
        }

        @Override
        protected void onPostExecute(String httpResponseMsg) {
            System.out.println("In onPostExecute");
            super.onPostExecute(httpResponseMsg);

            progressDialog.dismiss();

            if (httpResponseMsg.equalsIgnoreCase("It matches")) {

                finish();

                Intent intent = new Intent(MainActivity.this, StartActivity.class);
                System.out.println("USERNAME" + username);
                intent.putExtra("USERNAME", username);
                startActivity(intent);

            } else {
                mLoginFeedbackText.setText("Verification Failed, please try again.");
                mLoginFeedbackText.setVisibility(View.VISIBLE);
                mLoginProgress.setVisibility(View.INVISIBLE);
                loginBtn.setEnabled(true);
                Toast.makeText(MainActivity.this, httpResponseMsg, Toast.LENGTH_LONG).show();
            }

        }

        @Override
        protected String doInBackground(String... params) {
            System.out.println("In doInBackground");
            try {
                StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
                StrictMode.setThreadPolicy(policy);

                Class.forName("com.mysql.jdbc.Driver");
                Connection con = DriverManager.getConnection(url, user, pass);

                Statement st = con.createStatement();
                ResultSet rs = st.executeQuery("SELECT * FROM `users` WHERE username='BobMartin'");


                while (rs.next()) {
                    String queryPassword = rs.getString("password");
                    String hash_php = queryPassword.replaceFirst("2y", "2a");
                    if (BCrypt.checkpw(password, hash_php)) {
                        con.close();
                        System.out.println("It matches");
                        return "It matches";
                    } else {
                        System.out.println("It does not match");
                        return "It does not match";
                    }
                }
            } catch (ClassNotFoundException | SQLException e) {
                e.printStackTrace();
                System.out.println("result in catch");
            }
            return "It does not match";
        }
    }
    UserLoginClass userLoginClass = new UserLoginClass();
    userLoginClass.execute(username, password);
}


}

Similarly for other activity also im again creating connection and closing them in the similar manner as shown.

public class StartActivity extends AppCompatActivity {
Button startButton;
String userName;
private static final String url = "jdbc:mysql://192.168.0.103/pos";
private static final String user = "root";
private static final String pass = "";

ArrayList<String> dbQuestions = new ArrayList<String>();
ArrayList<String> dbAnswers = new ArrayList<String>();

ProgressDialog progressDialog;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    userName = getIntent().getStringExtra("USERNAME");
    new StartDb().execute();

    startButton = findViewById(R.id.startButton);
    startButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            System.out.println("USERNAMEstart" + userName);
            Intent intent = new Intent(StartActivity.this, BillActivity.class);
            Bundle args = new Bundle();
            args.putSerializable("ANSWERS", (Serializable) dbAnswers);
            args.putSerializable("QUESTIONS", (Serializable) dbQuestions);
            intent.putExtra("USERNAME", userName);
            intent.putExtra("BUNDLE", args);
            startActivity(intent);
        }
    });
}

@Override
public void onBackPressed() {
    // super.onBackPressed();
    Toast.makeText(StartActivity.this, "There is no back action", Toast.LENGTH_LONG).show();
    return;
}

class StartDb extends AsyncTask<String, Void, String> {

    @Override
    protected void onPreExecute() {
        System.out.println("In onPreExecute");
        super.onPreExecute();

        progressDialog = ProgressDialog.show(StartActivity.this, "Loading Data", null, true, true);
    }

    @Override
    protected void onPostExecute(String httpResponseMsg) {
        System.out.println("In onPostExecute");
        super.onPostExecute(httpResponseMsg);
        progressDialog.dismiss();
    }

    @Override
    protected String doInBackground(String... params) {
        System.out.println("In doInBackground");
        try {
            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
            StrictMode.setThreadPolicy(policy);

            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection(url, user, pass);

            Statement st = con.createStatement();
            ResultSet rs = st.executeQuery("SELECT * FROM `company_details`");

            while (rs.next()) {

                String que = rs.getString("questions");
                JSONObject obj1 = new JSONObject(que);
                for (Iterator<String> it = obj1.keys(); it.hasNext(); ) {
                    String key = it.next();
                    dbQuestions.add(obj1.getString(key));
                }

                String ans = rs.getString("answers");
                JSONObject obj2 = new JSONObject(ans);
                for (Iterator<String> it = obj2.keys(); it.hasNext(); ) {
                    String key = it.next();
                    dbAnswers.add(obj2.getString(key));
                }

                con.close();
            }
        } catch (ClassNotFoundException | SQLException | JSONException e) {
            e.printStackTrace();
            System.out.println("resilt in catch");
        }
        return "It does not match";
    }
}

}

Please suggest how can i increase execution time.

Answer 1

The MySQL protocol does not perform at all well over long distances. Its just a fact.

If you need to access MySQL over a long distance, you should put a rest/api in front of the database, running as physically close to the MySQL as you can, then get your app to query that, eg running multiple API-Gateways in containers for fail-over & load-balancing.

[MySQL]-[REST/API Gateway]-----------{Internet}------------[Client]

I've never used it, but looks like this sort of thing will do what you want - https://www.progress.com/odata/mysql

Or this "Auto-generate a REST API from an existing MySQL DB" - https://www.indiehackers.com/product/noco/auto-generate-a-rest-api-from-an-existing-mysql-db--Lt2CGDHrNrZVLZLMpaI

What rest/api you use depends on what back-end languages you feel the most comfortable with.

To be honest, what you really should be doing is putting a application specific rest/api in-front of your database so that, if the database credentials stored in your app get hacked, people can't just trash the database.

ie you should have a rest/api that imposes application specific security restrictions on what the client app can do.