Demo01
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class Demo01 {
public static void main(String[] args) {
//获取连接
try (Connection conn = DBUtils.getConn();) {
//创建SQL执行对象
Statement stat = conn.createStatement();
//执行SQL
String sql = "select ename from emp";
ResultSet rs = stat.executeQuery(sql);
while(rs.next()) {
String name = rs.getString("ename");
System.out.println(name);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Demo02
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
public class Demo02 {
public static void main(String[] args)
throws IOException {
//创建读取配置文件数据的对象
Properties p = new Properties();
//获取文件流
InputStream ips =
Demo02.class.getClassLoader()
.getResourceAsStream("jdbc.properties");
//把文件加载到属性对象中
p.load(ips);
//读取数据
String name = p.getProperty("name");
String age = p.getProperty("age");
System.out.println(name+":"+age);
}
}
Demo03
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbcp.BasicDataSource;
public class Demo03 {
public static void main(String[] args) throws SQLException {
//创建数据库连接池对象
BasicDataSource ds = new BasicDataSource();
//设置数据库连接信息
ds.setDriverClassName("com.mysql.jdbc.Driver");
ds.setUrl("jdbc:mysql://localhost:3306/newdb3");
ds.setUsername("root");
ds.setPassword("root");
//设置初始连接数量
ds.setInitialSize(3);
//设置最大连接数量
ds.setMaxActive(5);
//从连接池中获取连接 抛异常
Connection conn = ds.getConnection();
System.out.println(conn);
}
}
Demo04
import java.sql.Connection;
import java.sql.Statement;
import java.util.Scanner;
public class Demo04 {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.println("请输入用户名");
String username = s.nextLine();
System.out.println("请输入密码");
String password = s.nextLine();
//获取连接
try (Connection conn = DBUtils.getConn();) {
Statement stat = conn.createStatement();
String sql = "select count(*) from user "
+ "where username='"+username
+"' and password='"+password+"'";
//输出后在终端中测试
System.out.println(sql);
} catch (Exception e) {
e.printStackTrace();
}
}
}
DBUtils
package com.example.demo;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import org.apache.commons.dbcp.BasicDataSource;
public class DBUtils {
//创建DBCP连接池.BasicDataSource用池来管理Connection
private static BasicDataSource ds;
static {
//创建读取配置文件数据对象
Properties p=new Properties();
//获取文件流
InputStream ips=DBUtils.class.getResourceAsStream("application.yaml");
try {
//把文件加载到属性对象中
p.load(ips);
} catch (Exception e) {
//异常打印堆栈跟踪
e.printStackTrace();
}
String driver=p.getProperty("driver");
String url=p.getProperty("url");
String username=p.getProperty("username");
String password=p.getProperty("password");
//创建数据库连接对象,
ds=new BasicDataSource();
//设置数据库连接信息
ds.setDriverClassName(driver);
ds.setUrl(url);
ds.setUsername(username);
ds.setPassword(password);
//设置数据库连接数量
ds.setInitialSize(5);
//设置最大连接数量
ds.setMaxActive(100);
}
public static Connection getConn() throws Exception {
Connection conn=ds.getConnection();
return conn;
}
}