Basic application of JDBC

After downloading and configuring the JDBC driver, we can use it.

First, connect the database

There are three steps to follow when using JDBC to connect to a database to access data:

• Loading and registering the appropriate JDBC driver

Load using

Class.forName ();

After loading, the driver builds a driver object and causes Drivermanager.rigisterdriver () to register the object automatically.

Using URLs to identify the database in JDBC,

jdbc:< Sub-Protocol >:< sub-name >

When using MySQL, the syntax is as follows

Jdbc:mysql://hostname:port/databasename?param=value1

Sub-protocol: MySQL

Sub-name://hostname:port/databasename?param=value1, where param can have more than one.

For example:

jdbc:mysql://localhost:3306/sample?user=root&password=root;

• Establishes a connection object to the specified database

There are two ways of doing this:

1.

String url = "Jdbc:mysql://localhost:3306/sample?user=root&password=root";

Connection con = drivermanager.getconnection (URL);

2.

String url = "Jdbc:mysql://localhost:3306/sample";

String user = "root";

String password= "root";

Connection con = drivermanager.getconnection (Url,user,password);

• Submit database queries and get query objects

After acquiring the connection object for the database, it is possible to create a declarative object that is used primarily to transfer SQL statements to the database server and execute SQL statements.

As follows:

Statement stmt= con.createstatement ();

There are three ways to execute statements on statement objects:

ExecuteQuery (): Executes the query.

Executeupdate (): Perform the update.

Execute (): Do not know what is going to be done.

After execution, the database returns a ResultSet collection object into JDBC. The principle is as follows:

Connection------>preparedstatement-------->resultset

|------>statement----------------->resultset

|-------->callablestatement------>RESULTSET

Ii. using code to connect to a database

We first set up a Testmysql database with a student table in it.

Create Databse testmysql;//View Show databases;//build table user Testmysql;create table student (id int (3), name char, sex Boolean);//Add data insert into student (' 1 ', ' lishengjing ', ' 1 ');//View Data select * from student;

Then we load the JDBC, right-click Project in this project and select MySQL in the user library in Build path.

and finally the code. As follows

Package Chuiyuan;import Java.sql.connection;import Java.sql.drivermanager;import java.sql.resultset;import Java.sql.sqlexception;import Java.sql.statement;public class Jdbcexample {public static void main (String args[]) {try { Class.forName ("Com.mysql.jdbc.Driver"); String url = "Jdbc:mysql://localhost:3306/testmysql?user=root&password=chuiyuan"; Connection Connection = drivermanager.getconnection (URL); Statement stmt = Connection.createstatement (); ResultSet rs = stmt.executequery ("SELECT * from Student"), while (Rs.next ()) {System.out.println ("Student Number:" + Rs.getint (1)); System.out.println ("Student Name:" +rs.getstring (2)); System.out.println ("stutent sex:" + rs.getboolean (3) + "\ n");} Rs.close (); Stmt.close (); Connection.close ();} catch (ClassNotFoundException e) {e.printstacktrace ();} catch (SQLException e) {e.printstacktrace ();}}}

　　

　　

Basic application of JDBC