JDBC Connection Database Create connection object

Source: Internet
Author: User
Tags stmt

  

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

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