[JAVA] [Android] Connect to MySQL (unfinished)

JDBC download

You can't connect to the DB directly from Android, so you need a JDBC driver. If you didn't install MySQL, you can download and install it from this link called Connector / J. https://dev.mysql.com/downloads/

There is mysql-connector-java-8.0.18.jar in the hierarchy of C: \ Program Files (x86) \ MySQL \ Connector J 8.0, so add it to the build path.

Build path setting

Add the jar file under app / libs. In addition, add the following to build.gradle.

dependencies {
    compile files('libs/mysql-connector-java-8.0.18.jar)
}

After that, the sync button will probably appear, so sync.

・ Reference URL https://qiita.com/icchi_h/items/8ce738ce8511ef69c799

permission

Permission is required because it uses the network. Added the following.

<manifest>
    <uses-permission android:name="android.permission.INTERNET" />
</manifest>

Connection program to MySQL

MainActivity.java

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        try {
 //データベースに接続
            Connection con = MySqlConnect.getConnection();
 //ステートメントオブジェクトを作成
            Statement stmt = (Statement) con.createStatement();

            //SQL
            String mySql = "select date from table;";
            ResultSet rs = stmt.executeQuery(mySql);

            while(rs.next()) {
                Toast.makeText(getApplicationContext(), rs.getString("date"), Toast.LENGTH_LONG).show();
            }

 //オブジェクトを解放
            rs.close();
            stmt.close();
            con.close();

        } catch (Exception e) {
        }

MySqlConnect.java

class MySqlConnect{
  static Connection getConnection() throws Exception {
 //JDBCドライバのロード
    Class.forName("com.mysql.jdbc.Driver");
 //各設定
 String url = "jdbc: mysql: // hostname / dbname";
    String user = "user_name";
    String pass = "password";
 //データベースに接続
    Connection con = DriverManager.getConnection(url,user,pass);
    return con;
  }
}

・ Reference URL https://qiita.com/ks_513/items/0b286c4932a8e36c672e

Where in trouble

Currently, the following error has occurred and it is incomplete. ・ ** ClassLoader referenced unknown path ** -** java.lang.UnsupportedOperationException **

I tried setting the build path, reviewing the gradle file, etc., but I could not break through.

Impressions

I thought it would be easy, but it takes a lot of time. I've seen various sites, but I don't think it's relevant because there wasn't much written about asynchronous processing. But https://qiita.com/ks_513/items/0b286c4932a8e36c672e There is a statement at the bottom of that that asynchronous processing is better, so it seems worth trying.