[英]Error connecting Android Studio app to remote MySQL: java.sql.SQLNonTransientConnectionException: Could not create connection to database server
我正在尝试将 Android Studio 应用程序连接到远程 MYSQL 数据库，但显示无法创建与数据库的连接的错误。
我做了一些故障排除：
--- 有了这个，我认为这不是服务器问题。 ---
implementation group: 'mysql', name: 'mysql-connector-java', version: '8.0.22'
implementation group: 'mysql', name: 'mysql-connector-java', version: '8.0.23'
implementation group: 'mysql', name: 'mysql-connector-java', version: '8.0.13'
--- 有了这个，我注意到在 Gradle 中实现驱动程序不是错误，因为它显然正在识别驱动程序 ---注意：我目前正在使用 gradle 实现。
<uses-permission android:name="android.permission.INTERNET" />
Main class WITH ASYNCTASK (MainActivity.java) * 注意：这个 class 中的代码只是为了测试我是否能够从数据库中获取数据。 与我试图在应用程序本身中实现的任何功能无关。
public class MainActivity extends AppCompatActivity {
AlertDialog.Builder builder;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("Data");
new GetCultivos().execute();
builder.setPositiveButton("Accept", null);
AlertDialog dialog = builder.create();
dialog.show();
}
});
class GetCultivos extends AsyncTask<Void, Void, Void>{
String list = "Data = ";
@Override
protected Void doInBackground(Void... voids) {
CultivoDao cultivoDao = new CultivoDao();
List<Cultivo> listaCultivos = cultivoDao.obtenerCultivos();
for (Cultivo i : listaCultivos){
list = i.getIdCultivo() + " " + i.getNombre() + ", ";
}
return null;
}
@Override
protected void onPostExecute(Void eVoid){
builder.setMessage(list);
}
}
}
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.appmov, PID: 5699
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$4.done(AsyncTask.java:399)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:919)
Caused by: java.lang.NoClassDefFoundError: Failed resolution of: Ljava/sql/SQLType;
at com.mysql.cj.jdbc.DatabaseMetaData.getInstance(DatabaseMetaData.java:729)
at com.mysql.cj.jdbc.ConnectionImpl.getMetaData(ConnectionImpl.java:1180)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:446)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
at java.sql.DriverManager.getConnection(DriverManager.java:580)
at java.sql.DriverManager.getConnection(DriverManager.java:218)
at com.DAO.appmov.CultivoDao.StartConnection(CultivoDao.java:30)
at com.DAO.appmov.CultivoDao.obtenerCultivos(CultivoDao.java:49)
at com.example.appmov.MainActivity$GetCultivos.doInBackground(MainActivity.java:228)
at com.example.appmov.MainActivity$GetCultivos.doInBackground(MainActivity.java:220)
at android.os.AsyncTask$3.call(AsyncTask.java:378)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:919)
Caused by: java.lang.ClassNotFoundException: Didn't find class "java.sql.SQLType" on path: DexPathList[[zip file "/data/app/com.example.appmov-U33MrmDYU8kMl3MFpFCdcA==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.appmov-U33MrmDYU8kMl3MFpFCdcA==/lib/arm64, /system/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:196)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at com.mysql.cj.jdbc.DatabaseMetaData.getInstance(DatabaseMetaData.java:729)
at com.mysql.cj.jdbc.ConnectionImpl.getMetaData(ConnectionImpl.java:1180)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:446)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
at java.sql.DriverManager.getConnection(DriverManager.java:580)
at java.sql.DriverManager.getConnection(DriverManager.java:218)
at com.DAO.appmov.CultivoDao.StartConnection(CultivoDao.java:30)
at com.DAO.appmov.CultivoDao.obtenerCultivos(CultivoDao.java:49)
at com.example.appmov.MainActivity$GetCultivos.doInBackground(MainActivity.java:228)
at com.example.appmov.MainActivity$GetCultivos.doInBackground(MainActivity.java:220)
at android.os.AsyncTask$3.call(AsyncTask.java:378)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:919)
I/Process: Sending signal. PID: 5699 SIG: 9
Class 我用来连接数据库（CultivoDao.java）
public class CultivoDao {
private Connection connection;
private Statement statement;
//Method to start the connection
private void StartConnection() {
String url = "jdbc:mysql://remotemysql.com:3306/hUfMa4wLpe";
String usuario = ***HERE IS THE USERNAME***;
String password = ***HERE IS THE PASSWORD***;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
connection = DriverManager.getConnection(url, usuario, password);
statement = connection.createStatement();
} catch (Exception e) {
e.printStackTrace();
}
}
//Method to close the connection
private void CloseConnection(){
try {
connection.close();
} catch (Exception e) {
e.printStackTrace();
}
}
//Methog to get the data
public List<Cultivo> obtenerCultivos(){
List<Cultivo> listaCultivos = new ArrayList<>();
try {
StartConnection();
ResultSet rs = statement.executeQuery("Select * from cultivo");
while(rs.next()){
Cultivo cultivo = new Cultivo(rs.getInt("idCultivo"), rs.getString("nombre"));
listaCultivos.add(cultivo);
}
}catch (Exception e){
e.printStackTrace();
}
CloseConnection();
return listaCultivos;
}
}
Main class WITHOUT ASYNCTASK (MainActivity.java) * 注意：此 class 中的代码只是为了测试我是否能够从数据库中获取数据。 与我试图在应用程序本身中实现的任何功能无关。
public class MainActivity extends AppCompatActivity {
AlertDialog.Builder builder;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
builder = new AlertDialog.Builder(MainActivity.this);
String list = "Database list = ";
CultivoDao cultivoDao = new CultivoDao();
List<Cultivo> listaCultivos = cultivoDao.obtenerCultivos();
for (Cultivo i : listaCultivos){
list = i.getIdCultivo() + " " + i.getNombre() + ", ";
}
builder.setTitle("Data");
builder.setMessage(list);
builder.setPositiveButton("Accept", null);
AlertDialog dialog = builder.create();
dialog.show();
}
});
}
}
我使用的实际版本是没有 ASYNCTASK 的版本
我正在物理设备上测试这个应用程序。 我不知道这会以某种方式影响。
错误日志：
W/System.err: java.sql.SQLNonTransientConnectionException: Could not create connection to database server.
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:110)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
W/System.err: at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:1008)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
at java.sql.DriverManager.getConnection(DriverManager.java:580)
at java.sql.DriverManager.getConnection(DriverManager.java:218)
at com.DAO.appmov.CultivoDao.StartConnection(CultivoDao.java:30)
at com.DAO.appmov.CultivoDao.obtenerCultivos(CultivoDao.java:49)
at com.example.appmov.MainActivity$1.onClick(MainActivity.java:88)
at android.view.View.performClick(View.java:7870)
at android.widget.TextView.performClick(TextView.java:14970)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
at android.view.View.performClickInternal(View.java:7839)
at android.view.View.access$3600(View.java:886)
at android.view.View$PerformClick.run(View.java:29363)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
W/System.err: Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1565)
at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:115)
at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
at java.net.InetAddress.getAllByName(InetAddress.java:1152)
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:132)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65)
at com.mysql.cj.NativeSession.connect(NativeSession.java:152)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955)
... 22 more
java.lang.NullPointerException: Attempt to invoke interface method 'java.sql.ResultSet java.sql.Statement.executeQuery(java.lang.String)' on a null object reference
at com.DAO.appmov.CultivoDao.obtenerCultivos(CultivoDao.java:50)
at com.example.appmov.MainActivity$1.onClick(MainActivity.java:88)
at android.view.View.performClick(View.java:7870)
at android.widget.TextView.performClick(TextView.java:14970)
W/System.err: at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
at android.view.View.performClickInternal(View.java:7839)
at android.view.View.access$3600(View.java:886)
at android.view.View$PerformClick.run(View.java:29363)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
java.lang.NullPointerException: Attempt to invoke interface method 'void java.sql.Connection.close()' on a null object reference
at com.DAO.appmov.CultivoDao.CloseConnection(CultivoDao.java:40)
at com.DAO.appmov.CultivoDao.obtenerCultivos(CultivoDao.java:58)
at com.example.appmov.MainActivity$1.onClick(MainActivity.java:88)
at android.view.View.performClick(View.java:7870)
at android.widget.TextView.performClick(TextView.java:14970)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
at android.view.View.performClickInternal(View.java:7839)
at android.view.View.access$3600(View.java:886)
at android.view.View$PerformClick.run(View.java:29363)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
如何在不实施 PHP 的情况下解决此问题，这是我发现的另一种方式，因为我无法编辑托管数据库的服务器的任何内容。
谢谢！
ClassNotFoundException: Didn't find class "java.sql.SQLType"
Since java.sql.SQLType was added in Java 8, and doesn't exist at all on Android, you need to use a JDBC driver that is Java 7 compatible, which means you cannot use Connector/J 8.0, but must use version 5.1 .
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