[英]call method for mysql connection from main in java
我正在學習Java,我用netbeans添加了mysql連接器,我試圖做一個示例應用來查詢數據庫,但是我不知道如何從主方法中調用建立連接的方法。
這是我的代碼:
MySqlJdbcTest.java:
public class MySqlJdbcTest {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
// new com.mysql.jdbc.Driver();
Class.forName("com.mysql.jdbc.Driver").newInstance();
//conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?user=root&password=");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "";
conn = DriverManager.getConnection(connectionUrl, connectionUser, connectionPassword);
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT * FROM java");
while (rs.next()) {
String id = rs.getString("id");
String firstName = rs.getString("name");
String lastName = rs.getString("number");
System.out.println("ID: " + id + ", First Name: " + firstName
+ ", Last Name: " + lastName);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try { if (rs != null) rs.close(); } catch (SQLException e) { e.printStackTrace(); }
try { if (stmt != null) stmt.close(); } catch (SQLException e) { e.printStackTrace(); }
try { if (conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); }
}
}
}
這是test.java文件:
public class Test {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
MySqlJdbcTest prueba = new MySqlJdbcTest();
prueba();
}
}
您有2個main(String[])
方法。 Java要求您將其中之一作為應用程序的入口點。
如果我們假設Test.main()
是應用程序的入口點,則可以將另一個調用為
public static void main(String[] args) {
MySqlJdbcTest.main(args);
}
這等效於調用static
方法。
但是,為了使情況更清楚,建議您將MySqlJdbcTest.main()
方法重命名為其他名稱,並可能刪除static
修飾符和String[]
參數。 最終會像
public class MySqlJdbcTest {
public void executeSql() {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
// new com.mysql.jdbc.Driver();
Class.forName("com.mysql.jdbc.Driver").newInstance();
//conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?user=root&password=");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "";
conn = DriverManager.getConnection(connectionUrl, connectionUser, connectionPassword);
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT * FROM java");
while (rs.next()) {
String id = rs.getString("id");
String firstName = rs.getString("name");
String lastName = rs.getString("number");
System.out.println("ID: " + id + ", First Name: " + firstName
+ ", Last Name: " + lastName);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try { if (rs != null) rs.close(); } catch (SQLException e) { e.printStackTrace(); }
try { if (stmt != null) stmt.close(); } catch (SQLException e) { e.printStackTrace(); }
try { if (conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); }
}
}
}
由於該方法現在是實例方法,因此您需要一個類的實例才能在其上運行
public class Test {
public static void main(String[] args) {
MySqlJdbcTest prueba = new MySqlJdbcTest();
prueba.executeSql();
}
}
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