JDBC 连接数据库
一、什么是 JDBC
JDBC（Java DataBase Connectivity，Java 数据库连接）是一种用于执行 SQL 语句的 Java API，可以为多种关系型数据库提供统一访问，它由一组用 Java 语言编写的类和接口组成。JDBC 提供了一种基准，据此可以构建更高级的工具和接口，使数据库开发人员能够编写数据库应用程序，同时，JDBC 也是个商标名。
二、JDBC 连接数据库的步骤
（1）利用类的反射来获取驱动
Class.forName(driverClass)
加载 mysql 驱动：Class.forName("com.mysql.jdbc.Driver");
加载 oracle 驱动：Class.forName("oracle.jdbc.driver.OracleDriver");
（2）获得数据库连接对象 Connection
获取 mysql 连接
DriverManager.getConnection("jdbc:mysql://localhost:3306/libin?useUnicode=true&characterEncoding=UTF8",user,password);
获取 oracle 连接
DriverManager.gerConnection(URL,user,password);
DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","scott","123");
（3）创建语句
PreparedStatement ps = conn.prepareStatement(sql);
（4）执行语句得到结果集 ResultSet
ResultSet rs = ps.executeQuery();
（5）遍历结果集 ResultSet
（6）关闭连接、释放资源
三、连接数据的实例
创建项目、导入架包
1、连接 oracle 数据库
package com.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class TestOracleJDBC {
public static void main(String[] args) {
Connection conn = null;
try {
// 1.加载驱动
Class.forName("oracle.jdbc.driver.OracleDriver");
// 2.获取连接Connection对象
conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:orcl", "scott", "123456");
String sql = "select * from emp";
// 3.得到语句PreparedStatement
PreparedStatement ps = conn.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
// 4.遍历结果集
while (rs.next()) {
System.out.println(rs.getString("EMPNO") + " " + rs.getString("ENAME") + " " + rs.getString("MGR") + " " + rs.getString("HIREDATE") + " " + rs.getString("SAL") + " " + rs.getString("COMM") + " " + rs.getString("DEPTNO"));
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (conn != null) {
try {
// 5.关闭连接，释放资源
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
2、连接 mysql 数据库
package com.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class TestMysqlJDBC {
private static final String url = "jdbc:mysql://localhost:3306/springmvc?useUnicode=true&" + "characterEncoding=UTF8";
private static final String username = "root";
private static final String password = "123456";
public static void main(String[] args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
// 1.加载mysql驱动程序
Class.forName("com.mysql.jdbc.Driver");
// 2.获取连接对象
conn = DriverManager.getConnection(url, username, password);
String sql = "select * from student";
// 3.通过连接对象获得ps语句
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
// 4.遍历结果集
while (rs.next()) {
System.out.println(rs.getInt("sno") + " " + rs.getString("sname") + " " + rs.getInt("gender") + " " + rs.getInt("grade") + " " + rs.getInt("age"));
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
// 5.finally语句块中释放资源
} finally {
try {
if (rs != null) {
rs.close();
}
if (ps != null)
ps.close();
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}