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前言
在日常的开发当中，我们总是用框架去连接数据库，去完成业务中的需求，但是不可避免的有时候我们需要对数据进行额外的处理，
批量的修改或查询，这时候用框架就显得有点杀鸡用牛刀了，在这里我们将重温原始的JDBC操作，好记性不如烂笔头。
JDBC操作步骤
1.注册驱动
2.获取连接
3.获取预处理语句
4.添加占位符
5.结果遍历或者查询修改记录条数
6.释放资源
代码
1.导入数据库连接需要的jar包，这里使用maven
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
2.增删改查的测试
import org.junit.Test;
import java.sql.*;
public class DBTest {
/**
* 增
*
* @throws ClassNotFoundException
* @throws SQLException
*/
@Test
public void test01() throws ClassNotFoundException, SQLException {
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取连接
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "asdfmin");
//3.获得预处理语句
String sql = "insert into user (name, sex, age) values (? , ?, ?)";
PreparedStatement preparedStatement = conn.prepareStatement(sql);
//4.添加占位符
preparedStatement.setString(1, "jack");
preparedStatement.setString(2, "男");
preparedStatement.setString(3, "18");
//5.执行预处理语句
int i = preparedStatement.executeUpdate();
System.out.println("添加新记录条数：" + i);
//6.释放资源
preparedStatement.close();
conn.close();
}
/**
* 更
*
* @throws ClassNotFoundException
* @throws SQLException
*/
@Test
public void test02() throws ClassNotFoundException, SQLException {
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取连接
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "asdfmin");
//3.获取预处理语句
String sql = "update user set age = ? where name = ?";
PreparedStatement preparedStatement = conn.prepareStatement(sql);
//4.添加占位符
preparedStatement.setString(1, "19");
preparedStatement.setString(2, "jack");
//5.执行预处理语句
int i = preparedStatement.executeUpdate();
System.out.println("更新记录条数：" + i);
//6.释放资源
preparedStatement.close();
conn.close();
}
/**
* 删
*
* @throws ClassNotFoundException
* @throws SQLException
*/
@Test
public void test03() throws ClassNotFoundException, SQLException {
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取连接
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "asdfmin");
//3.获取预处理语句
String sql = "delete from user where id = ?";
PreparedStatement preparedStatement = conn.prepareStatement(sql);
//4.添加占位符
preparedStatement.setString(1, "1");
//5.执行预处理
int i = preparedStatement.executeUpdate();
System.out.println("删除记录条数：" + i);
//6.释放资源
preparedStatement.close();
conn.close();
}
/**
* 查
* @throws ClassNotFoundException
* @throws SQLException
*/
@Test
public void test04() throws ClassNotFoundException, SQLException {
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取连接
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "asdfmin");
//3.获取预处理语句
//String sql = "select * from user";
String sql = "select * from user where name = ?";
PreparedStatement preparedStatement = conn.prepareStatement(sql);
//4.添加站位符
preparedStatement.setString(1, "jack");
//5.执行预处理
ResultSet resultSet = preparedStatement.executeQuery();
//6.遍历结果集
while (resultSet.next()) {
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
String sex = resultSet.getString("sex");
String age = resultSet.getString("age");
System.out.println("id:" + id + " name:" + name + " set:" + sex + " age:" + age);
}
//7.关闭资源
resultSet.close();
preparedStatement.close();
conn.close();
}
}
3.说明
这里用的是预处理语句PreparedStatement（防止sql注入攻击）
对于JDBC的简单封装
对于频繁的注册驱动获取连接我们可以进行简单的封装
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class JDBCUtils {
private static final String DRIVERNAME = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://localhost:3306/test";
private static final String USER = "root";
private static final String PASSWORD = "asdfmin";
static {
try {
//1.注册驱动
Class.forName(DRIVERNAME);
} catch (ClassNotFoundException e) {
System.out.println("注册驱动失败");
e.printStackTrace();
}
}
public static Connection getConn() throws SQLException {
//2.获取连接
Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
//返回连接
return conn;
}
}
测试封装的JDBC工具类
import org.junit.Test;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class DBUtilTest {
/**
* 测试封装的JDBCUtil
*/
@Test
public void test01() {
Connection conn = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
//1.获取连接
conn = JDBCUtils.getConn();
//2.获取执行语句
String sql = "select * from user";
preparedStatement = conn.prepareStatement(sql);
//3.添加占位符
//4.执行预处理语句
resultSet = preparedStatement.executeQuery();
//5.遍历结果集
while (resultSet.next()) {
String name = resultSet.getString("name");
System.out.println("name:" + name);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//6.释放资源
try {
resultSet.close();
preparedStatement.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
API的一些简单说明
执行预处理语句的API
int executeUpdate(); --执行insert update delete语句.
ResultSet executeQuery(); --执行select语句.
boolean execute(); --执行select返回true 执行其他的语句返回false.
后记
温故而知新。