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; 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; 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();
}
}
} 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;
}
@Override
public String toString() {
return "Emp [id=" + id + ", name=" + name + ", salary=" + salary + "]";
}
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);
}
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);
}
}
}
到此基本实现了Dao模式通过JDBC操做数据库了。