Java DAO mode connects to database through JDBC

Java Program Access database:

1. Get the driver provided by the database vendor (Implementation class for the JDBC interface)

such as Ojdbc14.jar--Oracle database driver jar Package

Mysql-connector-java-5.1.8-bin.jar--mysql database driver jar Package

You can download it online.

2. Use the JDBC API to access the database

Connections,SQL statement execution, results

Java.sql.Driver: Each database vendor needs to implement this interface, the driver's tag

Java.sql.Connection: Encapsulation and database connection

Java.sql.Statement: Encapsulation of SQL statements to execute

Java.sql.ResultSet: Encapsulates the result set of a query

3. JDBC Programming steps

step1--Load Driver

step2--Getting a Connection object

step3--Executing SQL statements

step4--Processing Result Sets

step5--Closing Resources

4, the following gives the Connection database tool class (oneself writes the connection MySQL database, if wants to connect the oeacle can modify the corresponding parameter)

 Packagecom.day03;ImportJava.io.File;ImportJava.io.FileInputStream;Importjava.io.IOException;Importjava.sql.Connection;ImportJava.sql.DriverManager;ImportJava.sql.ResultSet;Importjava.sql.SQLException;Importjava.sql.Statement;Importjava.util.Properties; Public classConnectionutils {//Threading Single Example    Private Staticthreadlocal<connection> TL =NewThreadlocal<connection>(); Private StaticString URL; Private StaticString driver; Private StaticString username; Private StaticString password; Static{Properties props=NewProperties (); Try {            //The dependency file reads the database configuration information to load the configuration file as a class loadprops.load (connectionutils.class. getClassLoader (). getResourceAsStream ("Com/day03/db_mysql.properties")); } Catch(IOException e) {}if(Props! =NULL) {URL= Props.getproperty ("url"); Driver= Props.getproperty ("Driver"); Username= Props.getproperty ("username"); Password= Props.getproperty ("Password"); //mount and register the database driver            Try{class.forname (driver); } Catch(ClassNotFoundException e) {e.printstacktrace (); }        }    }     Public StaticConnection getconnection ()throwsSQLException {Connection con=Tl.get (); if(Con = =NULL) {con=drivermanager.getconnection (URL, username, password);        Tl.set (con); }        returncon; }     Public Static voidCloseConnection () {Connection con=Tl.get (); Try {            if(Con! =NULL) {con.close (); Tl.set (NULL); }        } Catch(SQLException e) {e.printstacktrace (); }    }     Public Static voidclosestatement (Statement stmt) {Try {            if(stmt! =NULL) {stmt.close (); }        } Catch(SQLException e) {e.printstacktrace (); }    }     Public Static voidCloseresultset (ResultSet rs) {Try {            if(rs! =NULL) {rs.close (); }        } Catch(SQLException e) {e.printstacktrace (); }    }         Public Static voidCloseAll (Statement stmt, ResultSet rs) {closeconnection ();        Closestatement (stmt);    Closeresultset (RS); }         Public Static voidMain (string[] args)throwsexception{System.out.println (Connectionutils.getconnection ()); }}

5. Configuration parameter File Db_mysql.properties

driver=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/testusername=Rootpassword =root

6. DAO mode operation database here is the code example

1) Emp.java

//entity class Public classEMP {Private intID; PrivateString name; Private Doublesalary;  Public intgetId () {returnID; } @Override PublicString toString () {return"Emp [id=" + ID + ", name=" + name + ", salary=" + salary + "]"; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     Public Doublegetsalary () {returnsalary; }     Public voidSetsalary (Doublesalary) {         This. Salary =salary; }     PublicEMP (intID, String name,Doublesalary) {        Super();  This. ID =ID;  This. Name =name;  This. Salary =salary; }     PublicEmp () {Super(); }     PublicEMP (String name,Doublesalary) {        Super();  This. Name =name;  This. Salary =salary; }}

2) DAO Interface class

Import java.util.List;  Public Interface Empdao {    Listthrows  Exception;}

3) Factory class

 Public class empdaofactory {    //  reads the class name of the implemented class in the file, instantiates public static by reflection      Empdao Getempdao () {        returnnew  empdaomysql ();}    }

4) DAO Interface implementation class

 Public classEmpdaomysqlImplementsempdao{ Public Static FinalString find_all_emp = "SELECT * from T_emp";//Query Statements         PublicList<emp> findallemp ()throwsexception{List<Emp> emplist =NewArraylist<emp>(); Connection Conn=connectionutils.getconnection (); PreparedStatement stmt=conn.preparestatement (find_all_emp); ResultSet RS=Stmt.executequery ();  while(Rs.next ()) {intid = rs.getint (1); String name= Rs.getstring (2); DoubleSalary = rs.getdouble (3); EMP EMP=NewEmp (ID, name, salary);        Emplist.add (EMP);        } connectionutils.closeall (stmt, RS); returnemplist; }}

5) Test class

 Public class empbiz {    publicstaticvoidthrows  exception{        =  Empdaofactory.getempdao ();        List<Emp> emplist = dao.findallemp ();          for (Emp e:emplist) {            System.out.println (e);     }}}

The basic implementation of the DAO mode through the JDBC operation database.

Java DAO mode connects to database through JDBC