Java程序访问数据库：

• 1、获取数据库厂商提供的驱动（jdbc接口的实现类）

如ojdbc14.jar——Oracle数据库驱动jar包

mysql-connector-java-5.1.8-bin.jar——MySQL数据库驱动jar包

自己去网上下载就行。

• 2、使用JDBC的API访问数据库

连接、SQL语句执行、结果

java.sql.Driver：各个数据库厂商需要实现该接口，驱动的标记

java.sql.Connection：封装和数据库的连接

java.sql.Statement：封装需要执行的SQL语句

java.sql.ResultSet：封装查询的结果集

• 3、JDBC编程步骤

step1——加载驱动

step2——获取连接对象

step3——执行SQL语句

step4——处理结果集

step5——关闭资源

• 4、下面给出连接数据库的工具类（自己写的连接MySql数据库，如要连接Oeacle可修改对应参数）

package com.day03;import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;//加入Java开发交流君样：756584822一起吹水聊天
public class ConnectionUtils {// 线程单例private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();private static String url;private static String driver;private static String username;private static String password;//加入Java开发交流君样：756584822一起吹水聊天static {Properties props = new Properties();try {// 从属性文件中读取数据库配置信息，以加载类的方式加载配置文件props.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");// 装载并注册数据库驱动try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}}//加入Java开发交流君样：756584822一起吹水聊天public static Connection getConnection() throws SQLException {Connection con = tl.get();if (con == null) {con = DriverManager.getConnection(url, username, password);tl.set(con);}return con;}public static void closeConnection() {Connection con = tl.get();try {if (con != null) {con.close();tl.set(null);}} catch (SQLException e) {e.printStackTrace();}}public static void closeStatement(Statement stmt) {try {if (stmt != null) {stmt.close();}} catch (SQLException e) {e.printStackTrace();}}public static void closeResultSet(ResultSet rs) {try {if (rs != null) {rs.close();}} catch (SQLException e) {e.printStackTrace();}}public static void closeAll(Statement stmt, ResultSet rs){closeConnection();closeStatement(stmt);closeResultSet(rs);}public static void main(String[] args) throws Exception{System.out.println(ConnectionUtils.getConnection());}}

5、配置参数文件db_mysql.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
username=root
password=root

6、Dao模式操作数据库下面是代码示例

1）Emp.java

//实体类
public class Emp {private int id;private String name;private double salary;public int getId() {return id;}@Overridepublic String toString() {return "Emp [id=" + id + ", name=" + name + ", salary=" + salary + "]";}//加入Java开发交流君样：756584822一起吹水聊天public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}public Emp(int id, String name, double salary) {super();this.id = id;this.name = name;this.salary = salary;}public Emp() {super();}public Emp(String name, double salary) {super();this.name = name;this.salary = salary;}
}

2)Dao接口类

import java.util.List;public interface EmpDao {List<Emp> findAllEmp() throws Exception;
}

3）工厂类

public class EmpDaoFactory {// 读取文件中实现类的类名，通过反射实例化public static EmpDao getEmpDao(){return new EmpDaoMySQL();}
}

4）Dao接口实现类

public class EmpDaoMySQL implements EmpDao{public static final String FIND_ALL_EMP = "select * from t_emp";//查询语句public List<Emp> findAllEmp() throws Exception{List<Emp> empList = new ArrayList<Emp>();Connection conn = ConnectionUtils.getConnection();PreparedStatement stmt = conn.prepareStatement(FIND_ALL_EMP);ResultSet rs = stmt.executeQuery();while(rs.next()){int id = rs.getInt(1);String name = rs.getString(2);double salary = rs.getDouble(3);Emp emp = new Emp(id, name, salary);empList.add(emp);}//加入Java开发交流君样：756584822一起吹水聊天ConnectionUtils.closeAll(stmt, rs);return empList;}
}

5）测试类

public class EmpBiz {public static void main(String[] args) throws Exception{EmpDao dao = EmpDaoFactory.getEmpDao();List<Emp> empList = dao.findAllEmp();for(Emp e : empList){System.out.println(e);}}
}