1.创建连接，下载MySQL驱动(JDBC接口的实现类，就是一个jar包)
public class Demo01 {
public static void main(String[] args)
throws ClassNotFoundException, SQLException {
//1. 注册驱动 告诉虚拟机使用的是哪个数据库软件
Class.forName("com.mysql.jdbc.Driver");
//2. 获取连接对象
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/newdb3", "root", "root");
System.out.println(conn);
//3. 创建SQL执行对象
Statement stat = conn.createStatement();
//4. 执行SQL语句
String sql = "create table jdbct1 (id int primary key,name varchar(10))";
stat.execute(sql);
System.out.println("执行完成！");
//5. 关闭资源
conn.close();
}
}
public class Demo02 {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/newdb3", "root", "root");
Statement stat = conn.createStatement();
String sql = "drop table jdbct1";
stat.execute(sql);
System.out.println("执行完成");
conn.close();
}
}
public class Demo03 {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/newdb3", "root", "root");
Statement stat = conn.createStatement();
//执行增删改SQL
// String sql = "insert into emp(empno,ename) values(100,‘Tom‘)";
// String sql = "update emp set ename=‘Jerry‘ where empno=100";
// String sql = "delete from emp where empno=100";
// stat.executeUpdate(sql);
//执行查询SQL
String sql = "select ename,sal,job from emp";
//查询到的结果装进了rs对象中
ResultSet rs = stat.executeQuery(sql);
//遍历结果集对象获取数据
while(rs.next()) {
//可以通过字段名和字段位置获取参数
String name = rs.getString(1);
double sal = rs.getDouble(2);
String job = rs.getString(3);
System.out.println(name+":"+sal+":"+job);
}
System.out.println("执行成功！");
conn.close();
}
}
2.DBUtil，返回一个Connection对象
public class DBUtils {
public static Connection getConn() throws Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/newdb3", "root", "root");
return conn;
}
}
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();
}
}
}
3.读取properties文件
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);
}
}
4.数据库连接池
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);
}
}
5.DBUtils，增强版本
public class DBUtils {
private static BasicDataSource ds;
static {
Properties p = new Properties();
InputStream ips = DBUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
try {
p.load(ips);
} catch (IOException e) {
e.printStackTrace();
}
String driver = p.getProperty("driver");
String url = p.getProperty("url");
String username = p.getProperty("username");
String password = p.getProperty("password");
//创建数据库连接池对象
ds = new BasicDataSource();
//设置数据库连接信息
ds.setDriverClassName(driver);
ds.setUrl(url);
ds.setUsername(username);
ds.setPassword(password);
//设置初始连接数量
ds.setInitialSize(3);
//设置最大连接数量
ds.setMaxActive(5);
}
public static Connection getConn() throws Exception {
//从连接池中获取连接 抛异常
Connection conn = ds.getConnection();
return conn;
}
}
6.预编译
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);
ResultSet rs = stat.executeQuery(sql);*/
//通过预编译的SQL执行对象解决SQL注入问题
String sql = "select count(*) from user where username=? and password=?";
PreparedStatement ps = conn.prepareStatement(sql);
//把？替换成真正的变量
ps.setString(1, username);
ps.setString(2, password);
//执行SQL语句
ResultSet rs = ps.executeQuery();
while(rs.next()) {
int count = rs.getInt(1);
if(count>0) {
System.out.println("登录成功！");
}else {
System.out.println("登录失败！");
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
7.批量操作
public class Demo05 {
public static void main(String[] args) {
String sql1 = "insert into emp(empno,ename) values(200,‘aaa‘)";
String sql2 = "insert into emp(empno,ename) values(201,‘bbb‘)";
String sql3 = "insert into emp(empno,ename) values(202,‘ccc‘)";
//获取连接
try (Connection conn = DBUtils.getConn();) {
Statement stat = conn.createStatement();
//添加到批量操作
stat.addBatch(sql1);
stat.addBatch(sql2);
stat.addBatch(sql3);
//执行批量操作
stat.executeBatch();
System.out.println("执行完成");
} catch (Exception e) {
e.printStackTrace();
}
}
}
public class Demo06 {
public static void main(String[] args) {
//create table person(name varchar(10),age int);
//获取连接
try (Connection conn = DBUtils.getConn();) {
String sql = "insert into person values(?,?)";
PreparedStatement ps = conn.prepareStatement(sql);
for (int i = 1; i <= 100; i++) {
ps.setString(1, "name"+i);
ps.setInt(2, 100+i);
//添加到批量操作
ps.addBatch();
//避免内存溢出每隔30条执行一次
if(i%30==0) {
ps.executeBatch();
}
}
ps.executeBatch();//执行批量操作
} catch (Exception e) {
e.printStackTrace();
}
}
}
8.返回自增主键
public class Demo08 {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.println("请输入员工姓名");
String name = s.nextLine();
System.out.println("请输入工资");
int sal = s.nextInt();
//获取连接
try (Connection conn = DBUtils.getConn();) {
String sql = "insert into myemp values (null,?,?)";
//设置获取自增主键值
PreparedStatement ps = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
//替换问号内容
ps.setString(1, name);
ps.setInt(2, sal);
ps.executeUpdate();
System.out.println("保存完成！");
//开始获取自增主键值
ResultSet rs = ps.getGeneratedKeys();
while(rs.next()) {
int id = rs.getInt(1);
System.out.println("自增主键值："+id);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
9.获取数据库本身信息
public class Demo10 {
public static void main(String[] args) {
//获取连接
try (Connection conn = DBUtils.getConn();) {
//获取数据库元数据对象
DatabaseMetaData dbmd = conn.getMetaData();
System.out.println("数据库名:"+dbmd.getDatabaseProductName());
System.out.println("数据库驱动版本:"+dbmd.getDriverVersion());
System.out.println("用户名:"+dbmd.getUserName());
//获取和表相关的元数据
String sql = "select * from emp";
Statement stat = conn.createStatement();
ResultSet rs = stat.executeQuery(sql);
//获取元数据对象
ResultSetMetaData rsmd = rs.getMetaData();
//获取字段数量
int count = rsmd.getColumnCount();
//遍历字段名和类型
for (int i = 0; i < count; i++) {
String name = rsmd.getColumnName(i+1);
String type = rsmd.getColumnTypeName(i+1);
System.out.println(name+":"+type);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
原文地址：https://www.cnblogs.com/hello4world/p/12190079.html
时间： 2024-10-14 11:44:54