Understanding of JDBC Fundamentals in Java EE learning

Definition of JDBC:

Java Data Base Connectivity,java database connection; is a Java API for executing SQL statements;

The steps of the JDBC operation:

　1. Registration Driver

Class.forName ();

2. Get the connection

Connection xxx=drivermanager.getconnection ();

3. Writing SQL

String sql= "";

4. Create PRECOMPILED statement performers

Preparestatement yyy=xxx.preparestatement (Sql,username,password);

5. Setting parameters

Yyy.getstring () or yyy.getint ();

6. Execute the query

Query operations

Yyy.executequery ();

Adding and removing changes operation

Yyy.executeupdate ();

7. Releasing Resources

???. close ();

Case:

1  PackageCn.it.jdbc;2 3 Importjava.sql.Connection;4 ImportJava.sql.DriverManager;5 Importjava.sql.PreparedStatement;6 ImportJava.sql.ResultSet;7 Importjava.sql.SQLException;8 Importjava.sql.Statement;9 Ten Importorg.junit.Test; One  A Importcom.jdbc.utlis.jdbcUtils; - ImportCom.jdbc.utlis.jdbcUtilsDemo; -  the  Public classHellodemo { - @Test -      Public voidMYJDBC ()throwsClassNotFoundException, SQLException { -         //1. Registration Driver +Class.forName ("Com.mysql.jdbc.Driver"); -         //2. Get the connection +Connection Connection =Drivermanager.getconnection ( A"Jdbc:mysql://localhost:3306/day01", "root", "root"); at         //3. Writing SQL -String sql = "SELECT * from User"; -         //4. Create a statement performer -PreparedStatement statement =connection.preparestatement (SQL); -         //5. Setting Parameters -  in         //6. Execute SQL statements -ResultSet ResultSet =statement.executequery (); to         //7. Traverse the results +          while(Resultset.next ()) { -System.out.println (resultset.getstring ("id") + "----" the+ resultset.getstring ("username")); *  $         }Panax Notoginseng resultset.close (); - statement.close (); the connection.close (); +     } A  the     //Test jdbcutils test method + @Test -      Public voidUtils () { $Connection Connection =NULL; $PreparedStatement statement =NULL; -  -         //Get Connections the         Try { -Connection =jdbcutils.getconnection ();Wuyi             //Writing SQL statements theString sql = "INSERT into user VALUES (?,?)"; -             //Statement pre-compilation Wustatement =connection.preparestatement (SQL); -             //Setting Parameters AboutStatement.setint (1, 5); $Statement.setstring (2, "Xiaoming"); -             //Execute SQL -             inti =statement.executeupdate (); -             //To determine if the statement executed successfully A             if(i = = 1) { +SYSTEM.OUT.PRINTLN ("OK!!!"); the}Else { -SYSTEM.OUT.PRINTLN ("NO!!!"); $             } the  the}Catch(ClassNotFoundException e) { the             //TODO auto-generated Catch block the e.printstacktrace (); -}Catch(SQLException e) { in             //TODO auto-generated Catch block the e.printstacktrace (); the}finally { About jdbcutils.closestatent (statement); the Jdbcutils.closeconn (connection); the  the         } +  -     } the Bayi     //Update Action the @Test the      Public voidUpdate () { -Connection Connection =NULL; -PreparedStatement statement =NULL; the         Try { the             //Registration Driver theClass.forName ("Com.mysql.jdbc.Driver"); the             //Get Connections -Connection =Drivermanager.getconnection ( the"Jdbc:mysql://localhost:3306/day01", "root", "root"); the             //SQ1 Statements theString sql = "UPDATE user SET username=?" where id=? ";94             //Create statement performer thestatement =connection.preparestatement (SQL); the             //Setting Parameters theStatement.setstring (1, "Er kang");98Statement.setint (2, 6); About             //Execute SQL statement - statement.executeupdate ();101}Catch(ClassNotFoundException e) {102             //TODO auto-generated Catch block103 e.printstacktrace ();104}Catch(SQLException e) { the             //TODO auto-generated Catch block106 e.printstacktrace ();107         }108         Try {109 statement.close (); the connection.close ();111}Catch(SQLException e) { the             //TODO auto-generated Catch block113 e.printstacktrace (); the         } the  the     }117 118     //Delete Operation119 @Test -      Public voidDelete () {121Connection Connection =NULL;122PreparedStatement preparestatement =NULL;123         Try {124Class.forName ("Com.mysql.jdbc.Driver"); theConnection =Drivermanager.getconnection (126"Jdbc:mysql://localhost:3306/day01", "root", "root");127String sql = "Delete from user where id=?"; -Preparestatement =connection.preparestatement (SQL);129Preparestatement.setint (1, 5); the             inti =preparestatement.executeupdate ();131             if(i = = 1) { theSystem.out.println ("OK");133             }134}Catch(ClassNotFoundException e) {135             //TODO auto-generated Catch block136 e.printstacktrace ();137}Catch(SQLException e) {138             //TODO auto-generated Catch block139 e.printstacktrace (); $         }141 142         Try {143 preparestatement.close ();144 connection.close ();145}Catch(SQLException e) {146             //TODO auto-generated Catch block147 e.printstacktrace ();148         }149  Max     }151}

JDBC

Understanding of JDBC Fundamentals in Java EE learning