Quick start JDBC

Quick start JDBC

1. The steps of writing code

1. Create a project , Import mysql Connected driver jar package
   Under the project under construction src Create a special storage driver in the directory jar The folder of the package – lib Local jar Copy to this directory
   take jar Add package as library file , Here's the picture ：
   
   

2. Registration drive
   Tips ：1.MySQL 5 Later driver package , You can omit the steps of registering the driver
   2. Automatic loading jar In bag META-INF/services/java.sql.Driver Driver class in file

Class.forName("com.mysql.jdbc.Driver");

3. Get the connection
   Java The code needs to be sent SQL to MySQL Server side , You need to establish a connection first

String url = "jdbc:mysql://127.0.0.1:3306/db1";
String username = "root";
String password = "1234";
Connection conn = DriverManager.getConnection(url, username, password);

4. Definition SQL sentence
   Define a String Data of type , Initialize to SQL sentence , Some operations on the database .（ Additions and deletions ）

5. Get the executed SQL sentence
   perform SQL Sentence needs SQL Perform object , And the execution object is Statement object

Statement stmt = conn.createStatement();

6. perform SQL sentence

stmt.executeUpdate(sql);// Return to one int Data of data type , Indicates the number of rows affected after execution 

7. Release resources

8. Return processing results

Sample code implementation ：

/** * JDBC Quick start  */
public class JDBCDemo {
    

    public static void main(String[] args) throws Exception {
    
        //1.  Registration drive 
        //Class.forName("com.mysql.jdbc.Driver");
        //2.  Get the connection 
        // If you access the local database locally , Can be abbreviated  jdbc:mysql:/// Database name ? Parameter key value pair 
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String username = "root";
        String password = "1234";
        Connection conn = DriverManager.getConnection(url, username, password);
        //3.  Definition sql
        String sql = "update account set money = 2000 where id = 1";
        //4.  Access to perform sql The object of  Statement
        Statement stmt = conn.createStatement();
        //5.  perform sql
        int count = stmt.executeUpdate(sql);// Rows affected 
        //6.  Processing results 
        System.out.println(count);
        //7.  Release resources 
        stmt.close();
        conn.close();
    }
}