JDBC Connection Database Create connection object

  

1. Load the JDBC driver:

• Before connecting to the database, first load the driver of the database you want to connect to the JVM (Java Virtual machine),
• This is achieved through the static method forname (String className) of the Java.lang.Class class.
• For example:
• try{
• Load the MySQL driver class
• Class.forName ("Com.mysql.jdbc.Driver");
• }catch (ClassNotFoundException e) {
• System.out.println ("Driver class not found, load driver failed!") ");
• E.printstacktrace ();
• }
• After a successful load, an instance of the driver class is registered in the DriverManager class.
• 2. Provide the URL of the JDBC connection
• ? The connection URL defines the protocol, sub-protocol, and data source identity when the database is connected.
• Writing form: Protocol: Sub-Protocol: Data source identification
• Protocol: Always start with JDBC in JDBC
• Sub-Protocol: A bridge-connected driver or database management system name.
• Data source identification: The tag locates the address of the database source and the connection port.
• For example: (MySQL connection URL)
• Jdbc:mysql:
• LOCALHOST:3306/TEST?USEUNICODE=TRUE&CHARACTERENCODING=GBK;    
• Useunicode=true: Indicates the use of the Unicode character set. If Characterencoding is set to
• gb2312 or GBK, this parameter must be set to true. CHARACTERENCODING=GBK: The character encoding method.
• 3. Create a connection to the database
• To connect to a database, you need to request and obtain a connection object from Java.sql.DriverManager.
• The object represents a connection to a database.
• ? Using the DriverManager getconnectin (string URL, string username,
• String password) method to pass in the path to the specified database to be connected, the user name of the database, and
• Password to get it.
• For example:
• Connect to MySQL database, user name and password are root
• String url = "Jdbc:mysql://localhost:3306/test";
• String username = "root";
• String password = "root";
• try{
• Connection con =
• Drivermanager.getconnection (URL, username, password);
• }catch (SQLException se) {
• SYSTEM.OUT.PRINTLN ("Database connection failed! ");
• Se.printstacktrace ();
• }
• 4. Create a statement
• To execute an SQL statement, you must obtain an java.sql.Statement instance that is divided into the following 3 statement instances
• Type of:
• 1. Execute static SQL statements. Typically implemented through statement instances.
• 2. Execute dynamic SQL statements. Typically implemented through PreparedStatement instances.
• 3. Execute the database stored procedure. Typically implemented through CallableStatement instances.
• The specific implementation method:
• Statement stmt = Con.createstatement ();
• PreparedStatement pstmt = con.preparestatement (sql);
• CallableStatement cstmt =
• Con.preparecall ("{Call Demosp (?,?)}");
• 5. Execute SQL statements
• The statement interface provides three ways to execute SQL statements: ExecuteQuery, executeupdate
• and execute
• 1, ResultSet executeQuery (String sqlString): Execute SQL statement that queries the database
• A result set (ResultSet) object is returned.
• 2, int executeupdate (String sqlString): Used to perform INSERT, UPDATE, or
• Delete statements and SQL DDL statements, such as CREATE table and drop table
• 3. Execute (sqlString): Used to perform a return of multiple result sets, multiple update counts, or a combination of the two
• Statement.
• Specific implementation code:
• ResultSet rs = stmt.executequery ("SELECT * from ...");
• int rows = Stmt.executeupdate ("INSERT into ...");
• Boolean flag = Stmt.execute (String sql);
• 6. Processing results
• Two cases:
• 1. The number of records affected by this operation is returned by performing the update.
• 2. The result of executing the query returned is a ResultSet object.
• ? ResultSet contains all rows that conform to the conditions in the SQL statement, and it provides a set of get methods for these
• Access to the data in the row.
• ? Get data using the access method of the result set (ResultSet) object:
• while (Rs.next ()) {
• String name = rs.getstring ("name");
• String pass = rs.getstring (1); This method is more efficient
• }
• (columns are numbered from left to right and start with column 1)
• 7. Close the JDBC Object
• All JDBC objects used are closed after the operation is complete to release the JDBC resource, turn off order harmony
• The opposite of the Ming Order:
• 1. Close record set
• 2. Closing the statement
• 3. Close the Connection object
• if (rs! = null) {//close Recordset
• try{
• Rs.close ();
• }catch (SQLException e) {
• E.printstacktrace ();
• }
• }
• if (stmt! = null) {//close declaration
• try{
• Stmt.close ();
• }catch (SQLException e) {
• E.printstacktrace ();
• }
• }
• IF (conn! = null) {//close connection object
• try{
• Conn.close ();

}catch (SQLException e) {e.printstacktrace ();

JDBC Connection Database Create connection object