JDBC Link database MySQL

 PackageCn.itcast.demo2;Importjava.sql.Connection;ImportJava.sql.DriverManager;ImportJava.sql.ResultSet;Importjava.sql.SQLException;Importjava.sql.Statement;Importorg.junit.Test; Public classDemo2 {/** Connect database, get connection even success! * To increase, delete and change the database.*/@Test Public voidFUN1 ()throwsClassNotFoundException, SQLException {/** First, get connection * 1. Prepare four parameters * 2. Load Driver class * 3. Get connection*/        //prepare four parametersString driverclassname = "Com.mysql.jdbc.Driver"; //the format of the JDBC protocol! JDBC: Name of Industry and commerce: Sub-Protocol (stipulated by Industry and commerce)//for MySQL, its sub-protocol structure://Host: Port number/database nameString url = "JDBC:MYSQL://LOCALHOST:3306/MYDB3"; String username= "Root"; String Password= "123"; //Load Driver classClass.forName (driverclassname); //use DriverManager, and save 3 parameters to get connectionConnection con =drivermanager.getconnection (URL, username, password); /** Second, to increase the database, delete, change * 1. Create a sender of statement * > statement statements through Connection objects, which is the function of sending SQL statements to the database! * 2. called its int executeupdate (String sql), which can send DML, DDL*/        //1. Get statement objects by connectionStatement stmt =con.createstatement (); //2. Send SQL statements using Statement! //String sql = "INSERT into Stu VALUES (' itcast_0003 ', ' Wangwu ', ' Male ')";//String sql = "UPDATE stu SET name= ' Zhaoliu ', age=22," +//"gender= ' female ' WHERE number= ' itcast_0003 '";String sql = "DELETE from Stu"; intR =stmt.executeupdate (SQL);    System.out.println (R); }        /*** Query Execution *@throwsClassNotFoundException *@throwsSQLException*/@Test Public voidFun2 ()throwsClassNotFoundException, SQLException {/** First, get connection * Two, get statement, send the SELECT statement * Three, the query returns the "form" to parse! */        /** One, Get connected * 1. Prepare four key connection parameters*/String Driverclassname= "Com.mysql.jdbc.Driver"; String URL= "Jdbc:mysql://localhost:3306/exam"; String username= "Root"; String Password= "123"; /** 2. Load Driver class*/Class.forName (driverclassname); /** 3. Call Drivermanger's getconnection () by the saved three parameters to get the connection*/Connection con=drivermanager.getconnection (URL, username, password); /** Second, get statement, execute SELECT statement * 1. Get Statement object: Connection's Createstatement () method*/Statement stmt=con.createstatement (); /** 2. Call Statement's ResultSet rs = executeQuery (String querysql)*/ResultSet rs= Stmt.executequery ("SELECT * from emp"); /** Three, analysis resultset * 1. Move the line cursor to the first line, you can call the next () method to complete! */         while(Rs.next ()) {//move the cursor down one line and determine if the next line exists!             intEmpno = Rs.getint (1);//get the value of the column by column number! String ename = rs.getstring ("ename");//get the value of the column by column name            DoubleSal = rs.getdouble ("Sal"); System.out.println (Empno+ "," + ename + "," +Sal); }                /** Four, close the resources * reverse off*/Rs.close ();        Stmt.close (); Con.close ();//this stuff, must be closed, not shut dead!     }        //Normalization@Test Public voidFUN3 ()throwsException {Connection con=NULL;//Defining ReferencesStatement stmt =NULL; ResultSet RS=NULL; Try {            /** One, Get connected*/String Driverclassname= "Com.mysql.jdbc.Driver"; String URL= "Jdbc:mysql://localhost:3306/exam"; String username= "Root"; String Password= "123";            Class.forName (Driverclassname); Con= drivermanager.getconnection (URL, username, password);//instantiation of                        /** Second, create statement*/stmt=con.createstatement (); String SQL= "SELECT * from emp"; RS=stmt.executequery (SQL); Rs.last ();//move the cursor to the last lineSystem.out.println (Rs.getrow ());                        Rs.beforefirst (); /** Three, loop through RS, print the data * * getString () and GetObject () is universal! *///While (Rs.next ()) {//System.out.println (Rs.getobject (1) + ","//+ rs.getstring ("ename") + "," + rs.getdouble ("Sal"));//            }                        intCount =rs.getmetadata (). getColumnCount ();  while(Rs.next ()) {//traversing rows                 for(inti = 1; I <= count; i++) {//traversing ColumnsSystem.out.print (rs.getstring (i)); if(I <count) {System.out.print (", ");            }} System.out.println (); }                    } Catch(Exception e) {Throw NewRuntimeException (e); } finally {            //Close            if(rs! =NULL) Rs.close (); if(stmt! =NULL) Stmt.close (); if(Con! =NULL) Con.close (); }            }}

JDBC Link database MySQL