【java基础】JDBC实现增删改查

package jdbc;
/**
* Java 在jdbc中的增删改查操作
* 1.PrepareStatement 是Statement的子接口，拥有其所有功能
* 2.PrepareStatement在大部分情况下性能更优
* 3.PrepareStatement能阻断大部分的sql注入攻击
* 综上所述，优先使用PrepareStatement
* @author Solitude
*
*/

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class MyJDBC {
private static final String url = "jdbc:mysql://localhost:3306/zsdx";
private static final String username = "root";
private static final String password = "root";

static{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}

// main方法，主函数入口
public static void main(String[] args) {
System.out.println("start");
MyJDBC.addUser();
MyJDBC.deleteUser(4);
User user = MyJDBC.selectUser(5);
System.out.println(user.getName() +" " + user.getPassword());
MyJDBC.alterUser(6);
System.out.println("stop");

}

//取得数据库链接
public static Connection getConn(){
Connection conn = null;
try {
conn = DriverManager.getConnection(url, username, password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}

//增加一个user
public static void addUser(){
String sql = "insert into user(name,password) values(?,?)";
Connection conn = MyJDBC.getConn();
try {
PreparedStatement ptst = conn.prepareStatement(sql);
ptst.setString(1, "hongda");
ptst.setString(2, "lilong123");
ptst.executeUpdate();
ptst.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

// delete a user
public static void deleteUser(int id){
String sql = "delete from user where id = ?";
Connection conn = MyJDBC.getConn();
try {
PreparedStatement ptst = conn.prepareStatement(sql);
ptst.setInt(1, id);
ptst.executeUpdate();
ptst.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

//Alter a user
public static void alterUser(int id){
String sql = "update user set name = ? where id = ?";
try {
PreparedStatement ptst = MyJDBC.getConn().prepareStatement(sql);
ptst.setString(1, "李龙");
ptst.setInt(2, id);
ptst.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public static User selectUser(int id) {
        String sql = "select * from user where id = ?";
        User user = new User();
        try {
            PreparedStatement ptst = MyJDBC.getConn().prepareStatement(sql);
            ptst.setInt(1, id);
            ResultSet rs = ptst.executeQuery();
            if(rs!= null){
                rs.next(); //把指针指向第一条数据
                user.setName(rs.getString("name"));
                user.setPassword(rs.getString("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return user;
    }
}

class User{
private int id;
private String name;
private String password;

public User() {

}

public User(String name, String password) {
super();
this.name = name;
this.password = password;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

}