如何检查dynamodb table中是否存在一个项目？
How to check whether an item exists in the dynamodb table?
我正在制作一个 android 应用程序，通过 Facebook 登录并自定义注册。我正在使用 AWS dynamodb 来存储用户数据。
我能够存储来自 Facebook 和自定义注册的数据，但无法扫描该数据。实际上，我希望每当用户使用自定义或 facebook 的 his/her 凭据返回登录时，应用程序应检查输入的字段是否存在于 table 中。如果不可用，应用程序将要求用户先注册。
MainActivity
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
Button login;
TextView signup;
TextView help;
EditText etUsername;
EditText etPassword;
String email;
String pass;
String email1;
String pass1;
private CognitoCachingCredentialsProvider credentialsProvider;
private CallbackManager callbackManager;
private LoginButton loginButton;
private ImageButton btnLoginFb;
private ProgressDialog progressDialog;
User user;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FacebookSdk.sdkInitialize(getApplicationContext());
setContentView(R.layout.activity_main);
etUsername = (EditText) findViewById(R.id.etUsername);
etPassword = (EditText) findViewById(R.id.etPassword);
login = (Button) findViewById(R.id.loginbutton);
signup = (TextView) findViewById(R.id.textViewsignup);
help = (TextView) findViewById(R.id.textViewHelp);
etUsername = (EditText) findViewById(R.id.etUsername);
etPassword = (EditText) findViewById(R.id.etPassword);
login.setOnClickListener(this);
signup.setOnClickListener(this);
help.setOnClickListener(this);
Context mContext = this.getApplicationContext();
credentialsProvider = new CognitoCachingCredentialsProvider(
mContext, // get the context for the current activity
"us-east-1:*******************************",
Regions.US_EAST_1
);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.loginbutton:
email = etUsername.getText().toString();
pass = etPassword.getText().toString();
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
if (email != null && pass != null) {
Intent slideactivity = new Intent(MainActivity.this, Welcome.class);
Bundle bndlanimation =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity, bndlanimation);
return;
}
else {
AlertDialog alertDialog = new AlertDialog.Builder(
MainActivity.this).create();
// Setting Dialog Title
alertDialog.setTitle("Oops");
// Setting Dialog Message
alertDialog.setMessage("No data found. You have to signup first!!!");
// Setting Icon to Dialog
//alertDialog.setIcon(R.drawable.tick);
// Setting OK Button
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// Write your code here to execute after dialog closed
startActivity(new Intent(MainActivity.this, SignUp.class));
}
});
// Showing Alert Message
alertDialog.show();
}
break;
case R.id.textViewsignup:
Intent slideactivity = new Intent(MainActivity.this, SignUp.class);
Bundle bndlanimation =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity, bndlanimation);
break;
case R.id.textViewHelp:
Intent slideactivity1 = new Intent(MainActivity.this, LoginHelp.class);
Bundle bndlanimation1 =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity1, bndlanimation1);
break;
}
}
@Override
protected void onResume() {
super.onResume();
callbackManager = CallbackManager.Factory.create();
loginButton = (LoginButton) findViewById(R.id.login_button);
loginButton.setReadPermissions("public_profile", "email", "user_friends");
btnLoginFb = (ImageButton) findViewById(R.id.btnLoginFb);
btnLoginFb.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setMessage("Loading...");
progressDialog.show();
loginButton.performClick();
loginButton.setPressed(true);
loginButton.invalidate();
loginButton.registerCallback(callbackManager, mCallBack);
loginButton.setPressed(false);
loginButton.invalidate();
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
callbackManager.onActivityResult(requestCode, resultCode, data);
}
private FacebookCallback<LoginResult> mCallBack = new FacebookCallback<LoginResult>() {
@Override
public void onSuccess(LoginResult loginResult) {
progressDialog.dismiss();
// App code
GraphRequest request = GraphRequest.newMeRequest(
loginResult.getAccessToken(),
new GraphRequest.GraphJSONObjectCallback() {
@Override
public void onCompleted(
JSONObject object,
GraphResponse response) {
Log.e("response: ", response + "");
try {
user = new User();
user.facebookID = object.getString("id").toString();
pass = user.facebookID;
Log.e(pass, "id");
user.email = object.getString("email").toString();
email = user.email;
Log.e(email, "email");
user.name = object.getString("name").toString();
user.gender = object.getString("gender").toString();
PrefUtils.setCurrentUser(user, MainActivity.this);
} catch (Exception e) {
e.printStackTrace();
}
Toast.makeText(MainActivity.this, "welcome " + user.name, Toast.LENGTH_LONG).show();
Intent intent = new Intent(MainActivity.this, Welcome.class);
startActivity(intent);
finish();
}
});
Bundle parameters = new Bundle();
parameters.putString("fields", "id,name,email,gender, birthday");
request.setParameters(parameters);
request.executeAsync();
new db().execute("");
}
@Override
public void onCancel() {
progressDialog.dismiss();
}
@Override
public void onError(FacebookException e) {
progressDialog.dismiss();
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private class db extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
Item item = new Item();
mapper.load(Item.class, email, pass);
if(item==null)
{
startActivity(new Intent(MainActivity.this,SignUp.class));
}
else{
item.setEmail(email);
item.setPass(pass);
mapper.save(item);
startActivity(new Intent(MainActivity.this,Welcome.class));
}
mapper.load(Item.class, email,pass);
if(item==null) {
startActivity(new Intent(MainActivity.this,SignUp.class));
}
else{
startActivity(new Intent(MainActivity.this,Welcome.class));
}
return "Executed";
}
@Override
protected void onPostExecute(String result) {
}
@Override
protected void onPreExecute() {
}
@Override
protected void onProgressUpdate(Void... values) {
}
}
Logcat:-
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask.done(AsyncTask.java:309)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
Caused by: com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMappingException: Null key found for public java.lang.String com.ediode.graphics3d.Item.getEmail()
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.getKey(DynamoDBMapper.java:434)
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:387)
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:466)
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:350)
at com.ediode.graphics3d.MainActivity$db.doInBackground(MainActivity.java:339)
at com.ediode.graphics3d.MainActivity$db.doInBackground(MainActivity.java:333)
at android.os.AsyncTask.call(AsyncTask.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
我从 4.5 小时开始就一直卡在这个问题上。如果有人能帮我解决这个问题那就太好了。
谢谢
您的映射器 class 的项目是什么样的？我将假设您将电子邮件作为没有范围键的哈希键，因为登录用户名应该是唯一的。您只需要对象的哈希键即可使用 load method 加载它。这是假设没有范围键。
试试这个。
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
// Use the password as the third parameter if it is a range key.
Item item = mapper.load(Item.class, email1);
if(item == null){
// That email is not in the database
}
else{
// Does exist in database, now compare password.
}
我正在制作一个 android 应用程序，通过 Facebook 登录并自定义注册。我正在使用 AWS dynamodb 来存储用户数据。
我能够存储来自 Facebook 和自定义注册的数据，但无法扫描该数据。实际上，我希望每当用户使用自定义或 facebook 的 his/her 凭据返回登录时，应用程序应检查输入的字段是否存在于 table 中。如果不可用，应用程序将要求用户先注册。
MainActivity
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
Button login;
TextView signup;
TextView help;
EditText etUsername;
EditText etPassword;
String email;
String pass;
String email1;
String pass1;
private CognitoCachingCredentialsProvider credentialsProvider;
private CallbackManager callbackManager;
private LoginButton loginButton;
private ImageButton btnLoginFb;
private ProgressDialog progressDialog;
User user;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FacebookSdk.sdkInitialize(getApplicationContext());
setContentView(R.layout.activity_main);
etUsername = (EditText) findViewById(R.id.etUsername);
etPassword = (EditText) findViewById(R.id.etPassword);
login = (Button) findViewById(R.id.loginbutton);
signup = (TextView) findViewById(R.id.textViewsignup);
help = (TextView) findViewById(R.id.textViewHelp);
etUsername = (EditText) findViewById(R.id.etUsername);
etPassword = (EditText) findViewById(R.id.etPassword);
login.setOnClickListener(this);
signup.setOnClickListener(this);
help.setOnClickListener(this);
Context mContext = this.getApplicationContext();
credentialsProvider = new CognitoCachingCredentialsProvider(
mContext, // get the context for the current activity
"us-east-1:*******************************",
Regions.US_EAST_1
);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.loginbutton:
email = etUsername.getText().toString();
pass = etPassword.getText().toString();
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
if (email != null && pass != null) {
Intent slideactivity = new Intent(MainActivity.this, Welcome.class);
Bundle bndlanimation =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity, bndlanimation);
return;
}
else {
AlertDialog alertDialog = new AlertDialog.Builder(
MainActivity.this).create();
// Setting Dialog Title
alertDialog.setTitle("Oops");
// Setting Dialog Message
alertDialog.setMessage("No data found. You have to signup first!!!");
// Setting Icon to Dialog
//alertDialog.setIcon(R.drawable.tick);
// Setting OK Button
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// Write your code here to execute after dialog closed
startActivity(new Intent(MainActivity.this, SignUp.class));
}
});
// Showing Alert Message
alertDialog.show();
}
break;
case R.id.textViewsignup:
Intent slideactivity = new Intent(MainActivity.this, SignUp.class);
Bundle bndlanimation =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity, bndlanimation);
break;
case R.id.textViewHelp:
Intent slideactivity1 = new Intent(MainActivity.this, LoginHelp.class);
Bundle bndlanimation1 =
ActivityOptions.makeCustomAnimation(getApplicationContext(), R.anim.animation, R.anim.animation2).toBundle();
startActivity(slideactivity1, bndlanimation1);
break;
}
}
@Override
protected void onResume() {
super.onResume();
callbackManager = CallbackManager.Factory.create();
loginButton = (LoginButton) findViewById(R.id.login_button);
loginButton.setReadPermissions("public_profile", "email", "user_friends");
btnLoginFb = (ImageButton) findViewById(R.id.btnLoginFb);
btnLoginFb.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setMessage("Loading...");
progressDialog.show();
loginButton.performClick();
loginButton.setPressed(true);
loginButton.invalidate();
loginButton.registerCallback(callbackManager, mCallBack);
loginButton.setPressed(false);
loginButton.invalidate();
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
callbackManager.onActivityResult(requestCode, resultCode, data);
}
private FacebookCallback<LoginResult> mCallBack = new FacebookCallback<LoginResult>() {
@Override
public void onSuccess(LoginResult loginResult) {
progressDialog.dismiss();
// App code
GraphRequest request = GraphRequest.newMeRequest(
loginResult.getAccessToken(),
new GraphRequest.GraphJSONObjectCallback() {
@Override
public void onCompleted(
JSONObject object,
GraphResponse response) {
Log.e("response: ", response + "");
try {
user = new User();
user.facebookID = object.getString("id").toString();
pass = user.facebookID;
Log.e(pass, "id");
user.email = object.getString("email").toString();
email = user.email;
Log.e(email, "email");
user.name = object.getString("name").toString();
user.gender = object.getString("gender").toString();
PrefUtils.setCurrentUser(user, MainActivity.this);
} catch (Exception e) {
e.printStackTrace();
}
Toast.makeText(MainActivity.this, "welcome " + user.name, Toast.LENGTH_LONG).show();
Intent intent = new Intent(MainActivity.this, Welcome.class);
startActivity(intent);
finish();
}
});
Bundle parameters = new Bundle();
parameters.putString("fields", "id,name,email,gender, birthday");
request.setParameters(parameters);
request.executeAsync();
new db().execute("");
}
@Override
public void onCancel() {
progressDialog.dismiss();
}
@Override
public void onError(FacebookException e) {
progressDialog.dismiss();
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private class db extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
Item item = new Item();
mapper.load(Item.class, email, pass);
if(item==null)
{
startActivity(new Intent(MainActivity.this,SignUp.class));
}
else{
item.setEmail(email);
item.setPass(pass);
mapper.save(item);
startActivity(new Intent(MainActivity.this,Welcome.class));
}
mapper.load(Item.class, email,pass);
if(item==null) {
startActivity(new Intent(MainActivity.this,SignUp.class));
}
else{
startActivity(new Intent(MainActivity.this,Welcome.class));
}
return "Executed";
}
@Override
protected void onPostExecute(String result) {
}
@Override
protected void onPreExecute() {
}
@Override
protected void onProgressUpdate(Void... values) {
}
}
Logcat:-
java.lang.RuntimeException: An error occurred while executing doInBackground() at android.os.AsyncTask.done(AsyncTask.java:309) at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354) at java.util.concurrent.FutureTask.setException(FutureTask.java:223) at java.util.concurrent.FutureTask.run(FutureTask.java:242) at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) at java.lang.Thread.run(Thread.java:818) Caused by: com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMappingException: Null key found for public java.lang.String com.ediode.graphics3d.Item.getEmail() at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.getKey(DynamoDBMapper.java:434) at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:387) at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:466) at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:350) at com.ediode.graphics3d.MainActivity$db.doInBackground(MainActivity.java:339) at com.ediode.graphics3d.MainActivity$db.doInBackground(MainActivity.java:333) at android.os.AsyncTask.call(AsyncTask.java:295) at java.util.concurrent.FutureTask.run(FutureTask.java:237) at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) at java.lang.Thread.run(Thread.java:818)
我从 4.5 小时开始就一直卡在这个问题上。如果有人能帮我解决这个问题那就太好了。
谢谢
您的映射器 class 的项目是什么样的？我将假设您将电子邮件作为没有范围键的哈希键，因为登录用户名应该是唯一的。您只需要对象的哈希键即可使用 load method 加载它。这是假设没有范围键。
试试这个。
AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider);
DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);
// Use the password as the third parameter if it is a range key.
Item item = mapper.load(Item.class, email1);
if(item == null){
// That email is not in the database
}
else{
// Does exist in database, now compare password.
}