java - 尝试通过 JDBC 将 mySQL DB 连接到 Android 时出错
问题描述
尝试通过 JDBC 将 mySQL DB 连接到 Android 时出现以下错误：
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836)
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456)
2020-06-28 21:08:57.969 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at java.sql.DriverManager.getConnection(DriverManager.java:580)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at java.sql.DriverManager.getConnection(DriverManager.java:218)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at com.example.mmi.DBUtility.connect(DBUtility.java:14)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at com.example.mmi.MainActivity.checkUser(MainActivity.java:99)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at com.example.mmi.MainActivity$2.onClick(MainActivity.java:49)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.view.View.performClick(View.java:7125)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.view.View.performClickInternal(View.java:7102)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.view.View.access$3500(View.java:801)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.view.View$PerformClick.run(View.java:27336)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.os.Handler.handleCallback(Handler.java:883)
2020-06-28 21:08:57.970 31747-31747/com.example.mmi W/System.err: at android.os.Handler.dispatchMessage(Handler.java:100)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: at android.os.Looper.loop(Looper.java:214)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: at android.app.ActivityThread.main(ActivityThread.java:7356)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: at java.lang.reflect.Method.invoke(Native Method)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
2020-06-28 21:08:57.971 31747-31747/com.example.mmi W/System.err: The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at java.lang.reflect.Constructor.newInstance0(Native Method)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.NativeSession.connect(NativeSession.java:144)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:956)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826)
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: ... 19 more
2020-06-28 21:08:57.972 31747-31747/com.example.mmi W/System.err: Caused by: java.net.SocketException: socket failed: EPERM (Operation not permitted)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at java.net.Socket.createImpl(Socket.java:492)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at java.net.Socket.getImpl(Socket.java:552)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at java.net.Socket.setTcpNoDelay(Socket.java:1012)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.protocol.StandardSocketFactory.configureSocket(StandardSocketFactory.java:94)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:147)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65)
2020-06-28 21:08:57.973 31747-31747/com.example.mmi W/System.err: ... 22 more
2020-06-28 21:08:58.015 31747-31788/com.example.mmi D/EGL_emulation: eglMakeCurrent: 0xe2da9260: ver 3 0 (tinfo 0xe2d99b40)
2020-06-28 21:08:58.026 31747-31788/com.example.mmi D/EGL_emulation: eglMakeCurrent: 0xe2da9260: ver 3 0 (tinfo 0xe2d99b40)
这是我的代码：
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DBUtility
{
public static Connection connect() throws IOException, ClassNotFoundException, SQLException {
Connection con =null;
Class.forName("com.mysql.cj.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://192.168.1.202:3306/mmi?useSSL=false", "username", "password");
return con;
}
}
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class MainActivity extends AppCompatActivity {
EditText mTextUsername;
EditText mTextPassword;
Button mButtonLogin;
TextView mTextViewForgot;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextUsername = (EditText) findViewById(R.id.edittext_username);
mTextPassword = (EditText) findViewById(R.id.edittext_password);
mButtonLogin = (Button) findViewById(R.id.button_login);
mTextViewForgot = (TextView) findViewById(R.id.textview_forgot);
mTextViewForgot.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
Intent forgotIntent = new Intent (MainActivity.this,ForgotActivity.class);
startActivity(forgotIntent);
}
});
mButtonLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view)
{
String user = mTextUsername.getText().toString().trim();
String pwd = mTextPassword.getText().toString().trim();
boolean res = checkUser(user, pwd);
if (res)
{
Toast.makeText(MainActivity.this, "Successfully Logged In", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(MainActivity.this, "Login Error", Toast.LENGTH_SHORT).show();
}
}
});
}
public boolean checkUser(String user, String pass)
{
boolean statement = false;
try {
Connection con = DBUtility.connect();
Statement st = con.createStatement();
statement = true;
ResultSet rs = st.executeQuery("SELECT * FROM mmi_userinfo where USERNAME='"+ user + "' and USER PASSWORD='" + pass + "'");
if (rs.next()) {
statement = true;
}
}catch (Exception e)
{
e.printStackTrace();
}
return statement;
}
}
我已经确认我的数据库正在运行，我已经刷新了我的 DNS，我将 my.cnf 文件适当地更改为 bind-address，并删除了 skip-networking 行。
我不确定是什么阻止了它的工作，任何帮助将不胜感激。
解决方案
您必须获取要连接的计算机的实际 IP 地址。127.0.0.1 指的是本地主机（在你的情况下，你的安卓手机或模拟器），这是一个错误的目的地。看看这里回答的问题
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