MySQL学习笔记_03
1 JDBC入门
1.1 回顾
之前操作mysql数据库：
1）使用mysql客户端工具
2）使用客户端连接mysql服务器
3）发送sql语句到mysql服务器，执行
1.2 什么是JDBC？
使用java程序发送sql语句到数据库服务器端执行，这叫用到了JDBC技术！！！！
dbc是Oracle-Sun公司设计的一套专门用于java程序操作数据库的接口。
1.3 使用jdbc发送sql条件
连接mysql数据库：
数据库主机
端口
数据库用户名
数据库密码
连接的数据库
1.4JDBC的核心API
Connection接口：与具体的数据库的连接对象。
StatementcreateStatement() 创建一个静态sql语句对象
PreparedStatementprepareStatement(String sql) 创建预编译的sql语句对象
CallableStatementprepareCall(String sql) 创建存储过程的sql语句对象
Driver接口：数据库驱动程序的接口，所有具体数据库厂商需要的驱动程序需要实现此接口。
Connectionconnect(String url, Properties info) 用于获取数据库连接
案例：演示三种连接数据库的方式
在写程序之前，先要导入jar包；
步骤：
1.在project中创建一个文件夹lib
2.把jar包复制放入lib
3.在要导入的jar包点右键，build path --> Configure Build Path
public class DriverDemo {
private static String url = "jdbc:mysql://localhost:3306/homework";
private static String user = "root";
private static String password = "root";
public static void main(String[] args) throws Exception {
conn1();
conn2();
conn3();
}
private static void conn3() throws Exception {
//mysql驱动程序的driver实现类对象的静态代码块中已经注册了驱动
//将Driver实现类对象加载到内存中，即可以完成注册
Class.forName("com.mysql.jdbc.Driver");
//获取连接
Connection conn = DriverManager.getConnection(url, user, password);
System.out.println(conn);
}
private static void conn2() throws Exception {
Driver driver = new com.mysql.jdbc.Driver();
//注册驱动
DriverManager.registerDriver(driver);
//获取链接
Connection conn = DriverManager.getConnection(url, user, password);
System.out.println(conn);
}
private static void conn1() throws Exception {
//创建一个驱动类对象Driver
Driver driver = new com.mysql.jdbc.Driver();
Properties prop = new Properties();
prop.setProperty("user", user);
prop.setProperty("password", password);
Connection conn = driver.connect(url, prop);
System.out.println(conn);
}
}
Statement接口：用于执行静态 SQL 语句
nt executeUpdate(String sql) 执行更新操作的sql语句 （create/alter/drop) DDL语句
public class Demo1 {
private static String url = "jdbc:mysql://localhost:3306/homework";
private static String user = "root";
private static String password = "root";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
//注册驱动
Class.forName("com.mysql.jdbc.Driver");
//获取连接
conn = DriverManager.getConnection(url, user, password);
//创建语句执行者
stmt = conn.createStatement();
String sql = "CREATE TABLE student("+
"id INT,"+
"NAME VARCHAR(20),"+
"age INT"+
");";
//执行sql语句
int count = stmt.executeUpdate(sql);
System.out.println(count);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}(insert/update/delete）DML语句
为了使代码更加简洁，我们先写一个JDBCUtil类，供我们使用
public class JDBCUtil {
private static String url = "jdbc:mysql://localhost:3306/homework";
private static String user = "root";
private static String password = "root";
static{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//获取连接
public static Connection getConn(){
try {
Connection conn = DriverManager.getConnection(url, user, password);
return conn;
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException();
}
}
//释放资源
public static void close(Connection conn,Statement stmt,ResultSet rs){
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stmt!=null){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}public class Demo2 {
public static void main(String[] args) {
testInsert();
testUpdate();
testDelete();
}
private static void testDelete() {
Connection conn = null;
Statement stmt = null;
try {
//获取连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "delete from student where id=1";
//获取语句执行者
stmt = conn.createStatement();
int count = stmt.executeUpdate(sql);
System.out.println(count);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new RuntimeException();
}finally{
JDBCUtil.close(conn, stmt, null);
}
}
private static void testUpdate() {
Connection conn = null;
Statement stmt = null;
try {
//创建连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "update student set name='Hins Chueng' where id=1";
//获取语句执行者
stmt = conn.createStatement();
int count = stmt.executeUpdate(sql);
System.out.println(count);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new RuntimeException();
}finally{
//释放资源
JDBCUtil.close(conn, stmt, null);
}
}
private static void testInsert(){
Connection conn = null;
Statement stmt = null;
//获取连接对象
try {
conn = JDBCUtil.getConn();
//定义sql
String sql = "insert into student values(1,'Hins',33)";
//获取语句执行者
stmt = conn.createStatement();
int count = stmt.executeUpdate(sql);
System.out.println(count);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new RuntimeException();
}finally{
JDBCUtil.close(conn, stmt, null);
}
}
}ResultSet executeQuery(String sql) 执行查询操作的sql语句(select)（DQL查询语句）
演示：
public class Demo3 {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
//获取连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "select * from student";
//获取语句执行者对象
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
while(rs.next()){
System.out.println(rs.getInt("ID")+"--"+rs.getString("name")+"--"+rs.getInt("age"));
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(conn, stmt, rs);
}
}
}PreparedStatement接口：用于执行预编译的 SQL语句（是Statement的子接口）
intexecuteUpdate() 执行更新操作的sql语句
ResultSetexecuteQuery() 执行查询操作的sql语句
演示：
public class Demo {
public static void main(String[] args) {
// testInsert();
// testUpdate();
// testDelete();
testSelect();
}
private static void testSelect() {
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = JDBCUtil.getConn();
String sql = "select * from student where id=?;";
stmt = conn.prepareStatement(sql);
stmt.setInt(1, 1);
rs = stmt.executeQuery();
while (rs.next()) {
System.out.println(rs.getInt("id")+"--"+rs.getString("name")+"--"+rs.getInt("age"));
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
JDBCUtil.close(conn, stmt, rs);
}
}
private static void testDelete() {
Connection conn = null;
PreparedStatement stmt = null;
try {
//创建连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "delete from student where id=?;";
//创建语句执行者对象
stmt = conn.prepareStatement(sql);
stmt.setInt(1, 2);
stmt.executeUpdate();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
JDBCUtil.close(conn, stmt, null);
}
}
private static void testUpdate() {
Connection conn = null;
PreparedStatement stmt = null;
try {
//创建连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "update student set name=? where id=?";
//创建语句执行者对象
stmt = conn.prepareStatement(sql);
stmt.setString(1, "Jacky Chueng");
stmt.setInt(2,2);
stmt.executeUpdate();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
JDBCUtil.close(conn, stmt, null);
}
}
private static void testInsert() {
Connection conn = null;
PreparedStatement stmt = null;
try {
//创建连接对象
conn = JDBCUtil.getConn();
//定义sql
String sql = "insert into student values(?,?,?);";
//创建语句执行者对象
stmt = conn.prepareStatement(sql);
stmt.setInt(1, 2);
stmt.setString(2, "Hins Chueng");
stmt.setInt(3, 33);
stmt.executeUpdate();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
JDBCUtil.close(conn, stmt, null);
}
}
}利用数据库完成登陆案例：
public class Login {
private static String user = "uu";
private static String password = "123456";
public static void main(String[] args) {
//用Statement做
Login1();
//用PreparedStatement做
Login2();
}
private static void Login2() {
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = JDBCUtil.getConn();
String sql = "select * from user where name=? and password=?";
stmt = conn.prepareStatement(sql);
stmt.setString(1, user);
stmt.setString(2, password);
rs = stmt.executeQuery();
if(rs.next()){
System.out.println("登陆成功");
}else{
System.out.println("登陆失败");
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(conn, stmt, rs);
}
}
private static void Login1() {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
//创建连接对象
conn = JDBCUtil.getConn();
//设置sql语句
String sql = "select * from user where name='"+user+"' and password='"+password+"'";
//创建语句执行者
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
if(rs.next()){
System.out.println("登陆成功");
}else{
System.out.println("登陆失败");
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(conn,stmt,rs);
}
}
}这里使用了PreparedStatement 和 Statement 两种方法来完成这个功能，但是如果使用Statement 验证登陆的话，会出现不安全的情况，就是在修改输入的用户名，在用户名后加入 ' OR 1=1 -- ，就会使代码恒成立，即当user表中有数据时，即使用户名和密码都错误，也可以完成登陆；
CallableStatement接口：用于执行 SQL 存储过程的接口（是PreparedStatement的子接口）
ResultSet executeQuery() 执行存储过程的sql语句
案例演示：
public class Demo {
public static void main(String[] args) {
//执行带输入输出参数的存储过程
test();
}
private static void test() {
// TODO Auto-generated method stub
Connection conn = null;
CallableStatement stmt = null;
ResultSet rs = null;
try {
conn = JDBCUtil.getConn();
String sql = "call Pro_NameById(?,?);";
stmt = conn.prepareCall(sql);
//给问号赋值
stmt.setInt(1, 1);
//如果存储过程带有输出参数的时候，首先需要注册，输出参数的类型
stmt.registerOutParameter(2, java.sql.Types.VARCHAR);
//发送并执行SQL
stmt.executeQuery();
System.out.println(stmt.getString(2));
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
JDBCUtil.close(conn, stmt, rs);
}
}
}ResultSet接口：结果集对象。 存储所有数据库查询的结果，用该对象进行数据遍历。
booleannext() ： 把光标移动到下一行。如果下一行有数据，返回true，如果没有下一行数据，返回false。
getXXX（列索引|列字段名称）： 获取字段的数据
图解：
使用方法类似迭代器，获取数据时时通过getInt getBoolean 等方法获取该字段数据；